Degenerative
Structural Disorders
Compressive
Structural Disorders
Compressive
disorders of the Median nerve
Compressive
disorders of the Ulnar nerve
Compressive
disorders of the Radial nerve
Compressive
disorders of the Sciatic,Peroneal and Tibial nerves
Other
compressive disorders of the lower extremities
A variety of neurological disorders
result from abnormalities of bones, ligaments, muscles, and other mesenchymal
tissue that compress the nervous system. In many instances the result is a
focal disorder of nervous system function such as a mononeuropathy, a root
syndrome, or the compression of intracranial contents by abnormalities of the
skull. Much of our clinical knowledge of the peripheral system is derived from
these kinds of lesions--for instance, the dermatomal map, which every student
of the nervous system carries in his or her black bag, is in part derived from
the study of patients with a herniated disc and root compression. Much of the
standard neurological examination of the sensory system is derived from studies
carried out by Henry Head 80 years ago in patients (including himself) who had
lesions of individual peripheral nerves.
Pathogenesis and
Pathophysiology. The vertebral disc is composed of the inner
gelatinous nucleus pulposus and the surrounding annulus fibrosus. Vertebral
disc herniation refers to rupture of the annulus with displacement of the
central nucleus. In youth, the disc is highly elastic. With the passage of
time, the direct vascular supply to the vertebrae and discs decreases, and they
undergo the accumulated effects of axial loading. The resulting decreases in
water and oxygen content, and metabolic efficiency lead to a disc that is more
compressible, less elastic, and more prone to tear and rupture. Disc rupture
and herniation can cause pain by several mechanisms. The periosteum of the bony
spine, the ligaments, the outer fibrous annulus of the vertebral discs, and the
dura are all innervated by nociceptive afferents from the spinal nerves. A
ruptured or torn fibrous disc may generate local pain owing to mechanical
stress on these pain-sensitive structures. Also, the exposed disc material has
a direct toxic effect and elicits a local inflammatory response, both of which
may promote increased pain sensitivity. In addition to these local effects, the
mass of the herniated disc material may compress the spinal roots by protruding
into the lateral recess or the neural foramen, or it may protrude into the
spinal canal, compressing the spinal cord in the cervical or thoracic region or
the cauda equina in the lumbosacral region. Details of the mechanisms by which
compression causes neurological dysfunction are complex and probably include
mechanical alteration of axonal membranes, impaired axonal flow, and ischemia
due to compromise of the microcirculation with resultant edema and eventual
demyelination. Finally, regional muscle spasm may accompany other effects,
adding to the pain and disability.
The accumulation of degenerative
lesions in the lumbosacral spine may compromise the area of the central canal
available to the cauda equina enough to cause symptomatic lumbar spinal
stenosis with or without discrete disc herniation. Most commonly, these lesions
include degenerative discs that bulge posteriorly, a hypertrophied ligamentum
flavum that bulges anteriorly, and hypertrophied facet joints that crowd into
the bony canal posterolaterally. Less common lesions may contribute to the
problem, hastening significant stenosis: congenitally short pedicles,
spondylolisthesis without spondylolysis, or abnormal angulation of the bony
spine.
Epidemiology and
Risk Factors. Vertebral disc degenerative changes are a universal
accompaniment of aging. Teenagers rarely develop symptomatic disc herniation.
The peak incidence of symptoms occurs between the ages of 30 and 50. Patients
often describe the onset of low back pain, usually remittent and without
specific features, in their twenties, perhaps after identifiable trauma, and
the onset of more specific symptoms that leads to the diagnosis of disc
herniation is often not preceded by further trauma. Probably the accumulation
of degenerative changes to the annulus and the preservation of the expansile
gelatinous nucleus, overlapping with a period of life when job and
sports-related activities increase the amount of mechanical stress on the body,
account for this peak in the incidence of disease. The incidence then falls off
in the older population, probably due to the lack of mobility of the desiccated
disc and the relative lack of physical activity. Women and men are affected
approximately equally.
There is a tendency toward disc
herniation in some families, such as those with congenital spinal anomalies,
including fused and malformed vertebrae and lumbar spinal stenosis due to short
pedicles. Patients with increased weight and tall stature are at increased risk
for this condition. Also, acquired spinal disorders, such as common
degenerative arthritis and ankylosing spondylitis, predispose to disc
degeneration. Various behaviors that increase risk include sedentary
occupations, physical inactivity, motor vehicle use, vibration, and smoking. In
younger women, pregnancy and delivery are associated with lumbosacral
herniation, and new symptoms of cervical disc herniation may occur in part
because of the bending and lifting involved in child rearing.
Clinical Features
and Associated Disorders. The most common site of disc herniation in the
cervical region is the C6-C7 level, followed by C5-C6, C7-T1, and C4-C5.
Patients typically develop some local pain in the neck that radiates to the
shoulders or the interscapular region. In the most common lateral herniations,
radicular symptoms ensue. These symptoms include pain in the shoulder and arm,
which may follow a dermatomal pattern but more typically is deep and aching and
only roughly corresponds to the involved dermatome. At the cervical levels, the
roots emerge laterally to exit through the neural foramina above the
correspondingly numbered vertebral bodies. Because the spinal cord and bony
vertebral levels are roughly aligned in the neck, the level of herniation
corresponds to the level of root irritation. Hence, C6-C7 herniation affects
the C7 root. Pain may be exacerbated by coughing or straining. Numbness is more
likely to supply reliable localizing information than pain. Compression of the
C6 root typically causes numbness in the thumb and index finger, and
compression of the C7 root typically involves the index and middle fingers.
When compression is severe, myotomal weakness, reflex loss, and, with time,
fasciculations and atrophy may ensue. With C6 compression, the biceps,
brachioradialis, pronator teres, and radial wrist extensors may be weak, and
the brachioradialis and biceps reflexes may be diminished or lost. With C7
weakness, the wrist and finger extensors and the triceps are typically weak.
The triceps reflex may also be diminished or lost. With C8 compression, there
is often interscapular pain and pain in the medial aspect of the arm and hand
with weakness of the hand intrinsic muscles. The finger flexor reflex may be
lost. Lesions above C6 are less common and are associated with correspondingly
more proximal sensory symptoms and weakness. Lesions of the C5 root may cause
shoulder pain and pain and numbness in the lateral aspect of the upper arm.
Many muscles can be used to test the C5 root, including the infraspinatus,
supraspinatus, deltoid, biceps, and supinator. Lesions above this level may
cause neck pain and sensory loss in the neck, supraclavicular area (C3), and
acromioclavicular area (C4) of the shoulder. Lesions involving the spinal cord
or roots above C4 may paralyze the diaphragm and cause respiratory compromise (
Table 29-1 ).
In the lumbosacral region, the most
common site of
TABLE 29-1 -- CERVICAL RADICULOPATHIES |
||||
Root |
Muscle
Weakness |
Action |
Location
of Pain |
Reflex
Change |
C5 |
Deltoid |
Shoulder
abduetion (15-90 degrees) |
Lateral shoulder |
Biceps |
Biceps |
Elbow
flexion |
Lateral
upper arm |
||
Supraspinatus |
Shoulder
abduction (0-15 degrees) |
Lateral
epicondyle |
||
Infraspinatus |
Humerus
external rotation |
|||
C6 |
Brachioradialis
(C5-C6) |
Elbow
flexion in semipronation |
Posterior
shoulder |
Brachioradialis |
Pronator
teres (C6-C7) |
Pronation |
Lateral
forearm |
||
ECR
(C6-C7) |
Radial
wrist extension |
Thumb and
index finger |
||
C7 |
Triceps
(C6-C8) |
Elbow
extension |
Posterior
shoulder |
Triceps |
ECR
(C6-C7) |
Radial
wrist extension |
Medial
forearm |
||
ED
(C7-C8) |
Finger
extension |
Index and
middle fingers |
||
C8 |
Flexor
pollieis longus |
Thumb
flexion |
Interscapular
medial forearm |
Finger
flexors |
FDS, FDP |
Finger
flexion |
Little
finger |
||
T1 |
Interossei |
Finger
abduction |
Medial
forearm |
None |
Abductor
digiti minimi |
Little
finger abduction |
Medial
epicondyle |
||
ECR,
Extensor carpi radialis; ED, extensor digitorum; FDS, Flexor digitorum
superficialis; FDP Flexor digitorum profundus Actual motor innervation is
multisegmental. Most of the myotomal overlap is disregarded here to emphasize
clinically useful localization. |
herniation is the L5-S1 level, followed by the L4-L5 level and then higher
levels. Symptoms of lumbosacral herniation often follow lifting or twisting
injuries, or they may result from accumulated low-level trauma. Pain typically
occurs in the parasacral area and radiates to the buttocks. Below C8, the roots
exit through the neural foramina below the correspondingly numbered
vertebral bodies. In patients with the most common posterolateral herniation,
dermatomal radicular pain typically occurs at the level below the emerging
root, which usually escapes entrapment above the protruding disc. Hence, L4-L5
herniation affects the L5 root . With posterolateral L5-S1 herniations and S1
root entrapment, the pain radiates to the posterior aspect of the thigh and,
especially when the root is stretched, into the posterolateral lower leg,
lateral heel, and sole. This pattern can be demonstrated by straight-leg
raising, in which the smaller the angle of elevation required to elicit pain,
the greater the suggestion that root compression is responsible. Characteristic pain on Some patients with symptoms elevation of
the opposite leg may be even stronger evidence of root compression. that
are exacerbated by root traction avoid full weight bearing on the heel of the
involved side, standing with the knee flexed and the heel off the floor. When
pain is less severe, symptoms may be elicited by having the patient walk on the
heels. Numbness is felt in the posterolateral leg, lateral aspect of the heel,
and the sole of the foot. The gastrocnemius and hamstrings may be weak, and the
ankle jerk may be diminished or lost. More lateral herniation of the L5- S1
disc or herniation of the L4-L5 disc may entrap the L5 root. Here the pain may
be similar, with adjustment of the findings to fit the L5 dermatome and
myotome. Numbness is most marked on the dorsum of the foot. Weak muscles
include the foot elevators (tibialis anterior group), everters (peronei), and
invertors (tibialis posterior), and the toe extensors (extensor hallucis
longus). Herniations at higher levels in the lumbosacral region cause pain and
deficits that correspond to the roots involved ( Table 29-2 ).
In addition to these radicular
syndromes, patients with central herniations in the cervical or thoracic region
may develop pain and acute myelopathic symptoms with spasticity and
quadriparesis or paraparesis, sensory loss at or below the segmental dermatome
of the lesion, hyperactive reflexes, and Babinski's signs. Soon after an acute
lesion develops, the reflexes may diminish because of spinal
TABLE 29-2 -- LUMBOSACRAL RADICULOPATHIES |
||||
Root |
Muscle
Weakness |
Action |
Location
of Pain |
Reflex
Change |
L1 |
Iliopsoas
(sometimes, but mainly L2-L3) |
Hip
flexion (mainly L2-L3) |
Inguinal
crease |
None |
L2 |
Iliopsoas
(L2-L3) |
Hip
flexion |
Anterior
and lateral thigh |
Cremasteric |
L3 |
Adductor
group |
Hip
adduction |
Medial
thigh and knee |
Knee |
Quadriceps |
Knee
extension |
|||
L4 |
Quadriceps |
Knee
extension |
Medial
lower leg |
Knee |
Tibialis
anterior |
Foot
dorsiflexion |
Medial
malleolus |
||
L5 |
EHL, EHB |
Great toe
extension |
Anterolateml
lower leg |
Tibialis
posterior |
EDL, EDB |
Toe
extension |
Dorsum of
foot |
Internal
hamstrings |
|
Tibialis
anterior |
Foot
dorsiflexion |
|||
Peroneii |
Foot
eversion |
|||
Tibialis
posterior |
Foot
inversion |
|||
Gluteus
medius |
Hip
abduction |
|||
Internal
hamstrings |
Knee
flexion |
|||
S1 |
Biceps
femoris |
Knee
flexion |
Lateral
heel |
Ankle |
Gastrocnemius
soleus |
Foot
plantar fiexion |
Sole of
foot |
||
FDB |
Toe
flexion |
|||
Gluteus
maximus |
Hip
extension |
|||
EHL,
Extensor hallucis longus; EHB, extensor hallucis brevis; EDL, extensor
digitorum longus; EDB, extensor digitorum brevis; FDB, flexor digitorum
brevis Actual motor innervation is multisegmental. Most of the myotomal
overlap is disregarded here to emphasize clinically useful localization. |
shock. Patients with lumbosacral central herniation may develop acute
compression of the cauda equina. This causes radicular pain, paresthesias, and
sensory loss referable to multiple bilateral roots, bilateral leg weakness, and
loss of the lower extremity reflexes. Bowel and bladder dysfunction may occur
early. When subtle, this dysfunction may be limited to asymptomatic bladder
retention noted only on postvoid catheterization. When dysfunction is more
severe, there may be perianal and perineal sensory loss, loss of anal tone and
reflexes (the reflex anal sphincter constriction due to perianal skin
stimulation or anal wink and the bulbocavernosus reflex), and fecal and urinary
retention and incontinence.
Degenerative herniations in the
thoracic region are uncommon, and symptoms and findings at these levels should
raise a suspicion of other underlying lesions, such as tumor or abscess. Disc
herniations at this level may cause radiating dermatomal pain resulting from
root compression; more frequently, they progress to spinal cord compression.
The symptom most suggestive of
lumbar spinal stenosis is neurogenic claudication. Low back pain radiates to
the buttocks and thighs and may extend more distally along the lumbosacral
dermatomes. This pain is brought on by walking. Unlike vascular claudication,
rest in the upright position does not relieve the pain, but rest while seated
or forward bending, such as leaning on a shopping cart, may provide relief.
Pain is exacerbated by spinal extension, such as downhill walking. When spinal
stenosis is severe, patients bend forward while walking. Symptoms and signs may
be either mechanical, due to bone, ligament, and joint involvement, or
radicular, due to compromise of the lateral recesses or neural foramina.
Proximal compression resulting from
root entrapment may increase the vulnerability of nerves to dysfunction due to
distal entrapment. This double crush phenomenon is presumed to be a result of
disturbed axoplasmic flow and disrupted architecture of the neurofilaments.
Therefore, when surgical repair of a distal entrapment fails to provide the
expected relief, a contributing radiculopathy resulting from degenerative disc
disease should be considered.
Differential
Diagnosis. Disc herniations must be differentiated from other
causes of acute and chronic neck, back, and extremity pain, radiculopathy, and
myelopathy. Malignant and benign tumors affecting the spine, infection,
epidural hematoma, various arthritides, including rheumatoid arthritis,
ankylosing spondylitis, and Reiter's syndrome, and other spondyloarthropathies
may present with similar early symptoms and signs. Various anomalies, such as
conjoined spinal roots and multiple roots emerging through a single foramen,
may also be confused with disc disease. Degenerative arthritis of the spine can
cause symptoms by many mechanisms, including disc herniation, and the various
lesions that are causing symptoms in a particular person should be
differentiated as clearly as possible to allow directed therapy.
Evaluation. A
careful history and physical examination are critical in the evaluation of disc
herniation. It has been well established with all imaging modalities that
asymptomatic patients have a high incidence of anatomical lesions. To properly
detect clinically relevant illness, it is therefore essential to establish the
closest possible clinical correlation of the symptoms and signs with the
anatomical findings of the various imaging studies. The initial history should
screen for problems that raise a suspicion of severe underlying disease. All
patients should be questioned about trauma, cancer, infections, recent fever,
and the use of anticoagulant medications. The underlying family history and
risk factors for tumor, infection, hematoma, and various disorders that
predispose to disc disease should be sought. The physical examination,
likewise, is undertaken to seek evidence of other severe underlying disease and
to localize and classify the pain and any deficits as mechanical, radicular, or
myelopathic. It is most important immediately to establish the presence of
major deficits that demand rapid diagnosis and treatment. These include the
cauda equina or conus syndrome, acute or progressive myelopathy, and severe
radicular motor deficits. If, on the other hand, the findings are consistent
with a ruptured disc and either no deficit or a mild to moderate one, it is
reasonable to temporize before pursuing a workup to fully evaluate the cause.
If plain radiographs of the affected area reveal no evidence of unexpected
lesions, conservative therapy for disc herniation may be tried before further
imaging is performed. This approach is justified by the good prognosis for
spontaneous recovery of patients with acute radiculopathy with mild to moderate
deficits. When the clinical examination leaves doubt about the localization of
the lesion, electromyography (EMG) can supplement the diagnosis of
radiculopathies and suggest other localizations, such as plexopathies and
neuropathies. Electromyography is more sensitive if it is delayed until at
least 10 to 14 days after the onset of a new deficit.
The tests available for imaging
include plain radiographs, computed tomography (CT), myelography with or
without CT, and magnetic resonance imaging (MRI). X-ray studies can be used to
screen for unexpected infection, tumor, or deformity of the bony spine.
Radiographs cannot show the neural tissues or the disc itself, but loss of disc
space height and other degenerative changes may provide some indirect
diagnostic information. Interpretation of plain radiographs must be tempered by
an awareness of the high frequency of degenerative findings in asymptomatic
populations. Plain radiographs taken under conditions of flexion and extension
can also be used to assess spinal stability. Myelography is invasive, indirect,
and nonspecific; however, it retains certain advantages in the era of MRI. It
can visualize the entire length of the spine and best defines the root sleeves.
Although myelography alone cannot distinguish between osteophytes and a
herniated disc compromising a foramen, when combined with CT, it provides the
best visualization of lateral pathology and small osteophytes. It is now most
commonly used to answer specific questions that remain after the MRI
examination. CT is superior to MRI in distinguishing soft tissue from bone. MRI
has emerged as the preferred imaging choice in most cases. It demonstrates bone
and soft tissues directly, easily allows multiplanar visualization, and is
suited to the visualization of multiple levels. The high contrast of epidural
fat and the cerebrospinal fluid (CSF)-filled thecal sac allows accurate
assessment of subtle compression in most cases.
Lumbar spinal stenosis is evaluated
by CT or MRI. MRI best demonstrates the relationship of the bony and neural
structures. CT best demonstrates lateral recess stenosis. Although the
dimensions of the bony canal can be used as guidelines, diagnosis must
ultimately be based on the correlation of stenosis with the clinical findings.
The transverse interfacet dimension should be greater than 16 mm. A dimension
of less than 10 mm indicates severe stenosis. An anteroposterior dimension of
less than 12 mm suggests stenosis; however, this finding is less sensitive in
patients with symptomatic disease. A lateral recess of 3 mm or less suggests
stenosis.
Management. The
crucial initial step in management of patients with disc herniation syndrome is
to identify those lesions that merit further evaluation and immediate therapy.
In the remaining cases, the good prognosis for early recovery justifies a trial
of conservative therapy before definitive imaging is done. Conservative therapy
includes rest in a position of comfort followed by early remobilization, gentle
exercises, and analgesics for pain as needed. Nonsteroidal anti-inflammatory
agents probably provide little relief in most cases. For severe pain, judicious
time- limited use of narcotics should be considered. Oral and epidural
corticosteroids can be helpful. Many other modalities are available, but there
are few reliable data about their effectiveness in populations: medical and
physical measures (e.g., ice, heat, massage, and ultrasound) that address
secondary muscle spasm, transcutaneous electrical nerve stimulation (TENS),
acupuncture, exercise, and traction. If improvement within the initial 4 to 6
weeks is not satisfactory, it is helpful to confirm the diagnosis by imaging.
This may provide a diagnosis of an unsuspected condition, localization for
epidural steroid injection, or information about suitability for eventual
surgery.
Clear indications for surgery
include the presence of acute myelopathy, cauda equina syndrome, severe or
progressive motor deficits, and intractable pain. When conservative measures
fail to provide a satisfactory response within 6 to 12 weeks, surgery should
also be considered. Studies comparing the outcome of surgical therapy with
conservative care suggest that early recovery occurs more often with surgery.
Although the benefits of surgery are lost with prolonged follow-up periods, it
is important to point out that in an often cited study, patients in the
conservative therapy group who had not responded to this therapy received
surgery. Newer microsurgical techniques allow shorter
hospitalization and rehabilitation periods but have not been shown to improve
long-term outcome. The success rate of chymopapain chemonucleolysis has not
reached that of surgery in most hands, and this treatment carries significant
risks. Percutaneous nucleotomy has also been disappointing and should not be pursued
given the current level of experience.
For patients with lumbar spinal
stenosis, initial therapy is symptomatic, with analgesics, pain-modulating
medications, and physical and occupational therapy. When significant disability
and pain remain despite conservative measures, referral for surgical
decompression should be considered.
Prognosis and
Future Perspectives. The prognosis for the relief of pain and a full
functional recovery is good. With bed rest alone, Weber found that 70 percent
of patients experienced decreased pain and improved function within 4 weeks,
and 60 percent had returned to work. Seventy percent were functionally
unrestricted at 1 year. With selective surgery, 90 percent of patients should
have a good functional recovery within a year. Patients with psychosocial
problems tend to do worse with either therapy, but those with appropriate
indications respond better to surgery. Sensory dysfunction does not recover as
fully as motor function, and a large proportion of patients retain some sensory
deficits. Patients in whom relapse occurs should be re-evaluated for new
lesions that are potentially addressable by surgery; however, the success rate
of surgery declines with follow-up procedures, and a significant proportion of
patients with disc herniation experience relapse with chronic low back pain.
Research into the mediators and
biomechanics of pain may further elucidate the mechanisms of pain in disc
disease and provide other conservative therapies. Improved imaging techniques
may further refine the selection of patients for surgery. It is hoped that
improved surgical selection and further refinements in surgical technique may
continue to improve outcome and shorten the period of disability.
Pathogenesis and
Pathophysiology. Degenerative changes of the spine universally
accompany aging, and the accumulation of such degenerative changes in the
cervical spine constitutes cervical spondylosis. These spondylotic changes
become clinically important when they cause pain or neurological dysfunction.
Aging leads to desiccation and shrinkage of the intervertebral discs. The
resultant loss of vertebral height narrows the intervertebral foramina. The
weakening of the containing fibrous annulus allows bulging of the desiccated
discs, which may then form transverse bars that protrude posteriorly,
compromising the spinal canal. Their protrusion more laterally into the
foramina may further compromise this space. Osteophytes and hypertrophic
osteoarthritic changes of the facet and uncovertebral joints may further
impinge on the spinal canal and foramina. Hypertrophy of the ligamentum flavum,
which runs longitudinally along the posterior wall of the spinal canal, may
compromise this space even more . Intuition suggests that compression of the
cervical spinal cord and nerve roots by the stenosis of the spinal canal and
foramina is responsible for the myelopathy and radiculopathies characteristic
of cervical spondylosis. However, a finer understanding of the pathogenesis of
this disorder has been elusive. Proposed explanations of the neurological
deficit include (1) direct compression by stenosis adequate to compromise the
cord and roots, (2) rubbing of the spinal cord and roots on protruding skeletal
structures that may not themselves be severely compressive, and (3) arterial or
venous compromise. All of these factors may play a role. Pathological study
shows the presence of distorted and flattened spinal cords that correspond to
spondylitic bars. Demyelination of the lateral columns occurs at the stenotic
site and caudally and of the posterior columns rostrally. This demyelination
corresponds to the sites of rubbing: anteriorly and inferiorly with neck
flexion and posteriorly and superiorly with extension. In the central gray
matter ischemic changes with neuronal loss are seen. Sometimes syringomyelia
can be found. Root sleeves may be thickened and rootlets adherent.
Epidemiology and
Risk Factors. The major risk factor for cervical spondylosis is
aging. Although trauma may contribute, there is usually no history of
significant trauma. Screening of asymptomatic patients shows a high frequency
of spondylotic changes that increases with advancing age. By age 59, 70 percent
of women and 85 percent of men have changes on radiographs, and by age 70, the
number increases to 93 percent of women and 97 percent of men. Up to 75 percent of these patients have
abnormal neurological findings by age 65, but fewer have symptoms of
spondylosis.
Heavy labor
and especially occupations that expose the patient to vibration probably
increase the risk of spondylosis.
Clinical Features
and Associated Disorders. The major clinical features are the symptoms and
signs referable to cervical myelopathy and radiculopathy. Patients may complain
of neck pain and pain radiating into the arms. There may be weakness of the
legs and sensory loss, especially of position sense. The weakness or sensory
loss may be discovered when an elderly patient presents for gait problems or
falls rather than as a direct complaint. Bowel and bladder dysfunction are
uncommon complaints accompanying advanced cervical myelopathy. Most commonly,
the onset of symptoms is insidious; however, occasionally an elderly patient
with spondylosis presents with catastrophic onset of quadriparesis or
paraparesis after a fall.
Typically, there is some limitation
of neck mobility. Examination of the cranial nerves should be normal, although
the jaw jerk may be increased in some cases. Weakness is common in the lower
extremities, especially in the iliopsoas, hamstrings, and extensors of the feet
and toes. Tone in the lower extremities is spastic, and Babinski's sign may be
present. Sensory loss to light touch, vibration, and joint position is
sometimes found. The major deficits in lower extremity function are determined
by the degree of myelopathy. Findings in the upper extremities vary depending
on the level of central canal stenosis and the degree of cervical root
involvement. Patients may have mild weakness with brisk reflexes. When roots
are compromised, especially in the lower cervical myotomes, atrophy, weakness,
and fasciculations may be found, at times mimicking the signs of amyotrophic
lateral sclerosis. Sensory loss in the upper extremities may also be seen,
following a simple radicular pattern or, more commonly, a patchy distribution,
presumably due to multiple root and cord involvement.
The main associated features are
those of disorders that compromise the cervical spine and predispose to
osteoarthritis. These include prior trauma, prior disc herniation, various
congenital anomalies of the cervical spine, and underlying systemic arthritic
disorders.
Differential
Diagnosis. The issue of differential diagnosis is particularly
important when one is dealing with a condition that is commonly present as an
asymptomatic radiological finding. When a patient presents with a combination
of radicular signs and symptoms accompanied by cervical myelopathy, the
diagnosis of spondylotic disease is not difficult. However, this clinical
presentation is not common, and most patients have either myelopathy resulting
from central protrusions or radiculopathy resulting from lateral protrusions,
but not both. The differential diagnosis must therefore cover conditions that
cause pure myelopathy, motor neuron disease, and combined myelopathy and
radicular or neuropathic lesions.
The syndrome of slowly progressive
spastic weakness of the extremities, worse in the lower than in the upper
extremities, may be produced by a variety of pathological causes. Some of these
are listed here along with clues that may help to distinguish them from
spondylotic myelopathy.
Multiple
Sclerosis Age of onset, gender, and types of neurological
findings do not reliably distinguish chronic spinal multiple sclerosis. Early
onset of bladder symptoms, visual complaints, and mental status changes should
be sought. Cranial MRI may demonstrate periventricular bright lesions on
T2-weighted images in the majority of patients with multiple sclerosis. Visual
evoked responses and oligoclonal bands in the CSF, if abnormal, are helpful.
Amyotrophic
Lateral Sclerosis In most
patients with amyotrophic lateral sclerosis, lower motor neuron signs are
evident from the beginning, but spasticity predominates in a few. The finding
of atrophy of muscle and increased reflexes in the same myotome strongly
suggests amyotrophic lateral sclerosis. Bulbar symptoms or signs should be
carefully sought on examination and should be evaluated with EMG. The sensory
loss from radicular or long tract involvement, common in cervical spondylosis,
should be absent. In one recent series, 5 percent of patients with amyotrophic
lateral sclerosis underwent a cervical laminectomy in the hope of arresting
progressive spasticity, emphasizing how commonly the two conditions coexist.
Primary Lateral
Sclerosis. A few patients with a slowly progressive, purely
spastic condition are found to have a degenerative disease allied to
amyotrophic lateral sclerosis, but without lower motor neuron features.
Subacute Combined
Degeneration of the Spinal Cord Vitamin B12
deficiency should never be overlooked. A low serum B12 level, hypersegmented polymorphonuclear leukocytes,
and macrocytic anemia are some of the abnormalities found in early cases. The
lesions of B12 deficiency begin
in the cervical or thoracic cord, and deficits are often primarily sensory,
which is quite uncommon in patients with cervical spondylosis.
Dural
Arteriovenous Fistula.Several decades ago it was believed that spinal
arteriovenous malformations presented either as subarachnoid hemorrhage or as
the lumbar syndrome of painful cauda equina deficit. It is now known that small
arteriovenous fistulas in the spinal dura can cause myelopathy with either a
stepwise progression or abrupt onset. Most malformations are seen on MRI or
myelography; however, some require selective angiography of the segmental
arteries that supply the cord for definitive diagnosis.
Myelopathy
Associated with AIDS A subacute vacuolar change in the spinal cord may
develop in patients with human immunodeficiency virus (HIV) infection, usually
in those with frank acquired immune deficiency syndrome (AIDS) and a history of
multiple opportunistic infections. Most patients are younger than the average
patient with spondylosis. The clinical findings often emphasize an ascending
sensory disorder.
HTLV-I Myelopathy A slowly progressive spastic paraparesis
with early bladder involvement in a patient from a region endemic for human
T-cell leukemia-lymphoma virus (HTLV)-I infection should prompt suspicion of
this infectious cause. Patients typically have milder spasticity of the upper
extremities. Diagnosis can be made by identifying the presence of antibodies to
HTLV-I in serum.
Familial Spastic
Paraplegia. These patients can be recognized by their family
history, usually that of an autosomal dominant disorder. No direct DNA testing
is available.
Syringomyelia.
Cervical syringomyelia may occur in isolation or in association with the Chiari
malformation, trauma, or tumor. Patients typically have lower motor neuron signs
in the upper extremities due to involvement of the central gray matter and
upper motor neuron signs in the upper and lower extremities due to involvement
of the descending corticospinal tracts. The segmental loss of spinothalamic
modalities of sensation and the neuropathic quality of the accompanying neck,
back, and extremity pain as well as the context of an associated underlying
problem suggest the diagnosis. MRI demonstrates the syrinx.
Compressive
Lesions at the Craniocervical Junction. The Chiari malformation
may cause myelopathy, vertigo, and ataxia. There may be an associated
syringomyelia. Basilar impression due to instability of the atlanto-occipital
joint or atlantoaxial instability, as in rheumatoid arthritis, may cause slowly
progressive myelopathy. These lesions often occur in the context of spondylotic
lesions, and it is very important to clarify the source of progressive
findings. Certain tumors, such as meningiomas and schwannomas, at the
craniocervical junction may also mimic the signs of cervical spondylosis. Often
the history suggests a loss of function on one side followed by progression of
signs to all four extremities. Down-beating nystagmus suggests the
localization. Imaging high enough to demonstrate the craniocervical junction is
crucial before cervical myelopathy is attributed to spondylotic lesions.
Evaluation.
Evaluation begins with a careful history and examination. This is especially
important because of the known high rate of radiological spondylotic
abnormalities in asymptomatic populations. It is very important to establish
the best possible correlations between the clinical findings and the imaging
abnormalities. Available imaging modalities include plain radiographs, CT
myelography, and MRI. Plain films can show many of the degenerative changes of
bony elements; however, they do not reveal the relationship of these to the
neural structures. Simple flexion and extension films performed with care can
also demonstrate spinal instabilities that are not apparent on MRI or CT myelography.
MRI is the easiest noninvasive means of diagnosis. MRI can demonstrate the
dimensions of the spinal canal and foramina and distortion of the spinal cord
and roots caused by the impingement of bony structures. Gadolinium enhancement
can demonstrate the presence of various alternative lesions that may be under
consideration. CT myelography can be used to answer any questions that remain
after MRI. The myelogram may fail to show complete block even when significant
spondylotic myelopathy is present.
Management.
Conservative management of cervical spondylosis includes immobilization with a
cervical collar and the use of non-narcotic, nonsteroidal medications for pain.
The symptoms and signs in most patients stabilize with this therapy; that is,
the myelopathy does not progress, and in some patients it improves. Yet
controlled studies evaluating the benefit of immobilization have not been done.
When radicular pain is the major problem demanding further intervention,
epidural steroid injections can be effective. We refer patients for
neurosurgical evaluation and surgical therapy when their myelopathy progresses
despite these conservative measures, after careful consideration of other
diagnostic possibilities as listed earlier. There has been no documentation of
long-term benefit from surgery, although many series have shown evidence of
benefit in the short term. Posterior decompressive laminectomy is the
procedure that has the longest history. However, unless it is performed over
many levels, it will not relieve multilevel compression. Wide decompression
performed over a number of segments may be complicated in later years by a swan
neck deformity owing to the loss of posterior supporting elements. The anterior
approach with interbody fusion is especially suitable for patients with single
level nerve root compression. Its benefits for cord compression are less well
defined. When radicular symptoms are due to bony osteophytes, foraminotomy may
relieve the symptoms and signs of root compression. Although the benefit of
surgery has not been systematically validated, and many patients improve
spontaneously or with immobilization by a collar, clinical experience with
individual cases suggests that selected patients do benefit and show marked
improvement shortly after decompressive surgery.
Prognosis and
Future Perspectives. The natural history of cervical spondylosis is not
known. Although the course of the disease is progressive and most patients have
chronic symptoms, the large majority remain stable for many years and do not
require surgical intervention.
MRI has greatly advanced the
precision of diagnosis while sparing most patients the discomfort and risk of
myelography. Future advances in imaging may further facilitate diagnosis.
Rowland has pointed out our great lack of knowledge of the natural history of
cervical spondylosis as well as the need for controlled trials to demonstrate
the effects of surgery and clarify surgical indications. Such studies, if they are done, will require
a cooperative effort and careful definition of clinically relevant questions.
Ankylosing spondylitis (AS) is one
of the group of seronegative forms of arthritis, which also includes Reiter's
syndrome and psoriatic arthritis. There is a close association with the HLA-B27
type, and the disease is more than three times more common in men than in
women. In many patients, the disease seems to progress slowly for years,
primarily with back pain, and then stabilizes without much disability. In some
cases the disease progresses to total spinal fusion, producing a typical bamboo
spine on x-ray criteria. In all patients, the presence of sacroiliac joint
disease on radiographs is required to make the diagnosis. There are two major
neurological complications of AS: a cauda equina syndrome of unclear etiology,
and several types of cervical spinal cord compression due to dislocation or
deformity.
Ankylosing spondylitis is less
common in black populations and in people of Japanese ancestry, in parallel
with the lower expression of HLA-B27 in these groups. There is a considerable
familial incidence of AS. Approximately 20 percent of patients with AS have
joint disease in the peripheral joints, not in the vertebral column or pelvis,
and it is in this group that the neurological complications seem to be most
frequent.
Patients with the cauda equina
syndrome of AS
have a gradual
and relatively symmetrical loss of function in the L5, S1, and S2 roots. Both
motor and sensory fibers are affected. Foot drop, weakness of plantar flexion,
and perianal sensory loss are typical. Nearly all patients develop bladder and
bowel incontinence. The cervical spine disorder most often associated with AS
is instability at the craniocervical junction because of ligamentous laxity at
the level of the odontoid process. Some patients have stepwise subluxation of
the cervical spine, resembling that seen in seropositive rheumatoid arthritis.
In either case, myelopathy may develop, often with significant sensory loss in
the hands, as well as quadriparesis. As in rheumatoid arthritic disease, there
may be marked instability of the cervical spine or craniocervical junction with
much local pain, sudden changes in neurological symptoms with postural change,
and eventual requirement for surgical fusion. Patients with AS may have uveitis
or cardiac disease. Fractures of the fully or partially fused spine, especially
if osteopenia exists, are common.
The cauda equina syndrome can be
confused with lumbar disc disease, but the distinguishing features of the
former are symmetry and early loss of bladder function. The craniocervical
instability of AS produces a myelopathy that may be insidious and difficult to
distinguish from general weakness, myopathy, nerve entrapment, or generalized
neuropathy.
The diagnosis should be confirmed
radiologically; there are specific criteria for the diagnosis of AS. Cauda equina syndrome is accompanied by a
distinctive radiological change, consisting of a wide patulous distention of
the subarachnoid space in the sacral region, often with erosion of the
overlying sacral bone. The cause of this distended space is unknown, nor is it
clear how this distention contributes to nerve root dysfunction. CSF
examination does not suggest an arachnoiditis. The cervical spine should be
fully visualized by MRI, and the position of the odontoid should be carefully
noted. In rheumatoid arthritis patients, asymptomatic widening of the space
between the odontoid and the arch of C1 (normally 3 mm or less) is observed. In
AS, unrecognized fracture, odontoid dislocation, or atlantoaxial dislocation
can occur.
Unfortunately, no specific therapy
is available for patients with the cauda equina syndrome. A scattering of case
reports indicate that some authors have attempted decompression of the thecal
sac. Decompressive
laminectomy is of no value. Fractures or cervical dislocations may
require fusion.
Pathogenesis and
Pathophysiology. Our understanding of the pathogenesis of fibrous
dysplasia has advanced greatly in recent years. Several investigators have
identified a point mutation in the gene that codes for the alpha subunit of the
G-protein, Gsa, in affected bone and other tissues in patients with fibrous
dysplasia. The absence of this mutation in non-affected tissues in patients
with the disease suggests that a somatic mutation occurs early in embryogenesis
to create a genetic mosaic. The mutated Gsa proteins activate adenylate cyclase
and increase signaling through the cyclic adenosine monophosphate (cAMP)-
protein kinase A pathway. Recent work suggests that the resultant
phosphorylation of transcription factors enhances transcription of the
proto-oncogene c-fos and translation of c-fos protein in affected
tissues. These findings surely represent only part of
the molecular story, and it is likely that enhanced production of other
oncoproteins is yet to be discovered. These molecular changes result in a gain of
function that probably underlies the bony and endocrinological lesions
characteristic of fibrous dysplasia. The functional result is a disorder of
lamellar bone remodeling and repair. The pathological result is a replacement
of normal bone and marrow elements by a vascular fibrous tissue composed of
whorls of proliferating fibroblasts with haphazardly arranged trabeculae of
metaplastic bone and fluid-filled cystic areas lined by multinucleated giant
cells. The appearance is similar to that of osteitis fibrosa cystica due to
hyperparathyroidism but is distinguished by the absence of osteoblasts. The
abnormal bone originates from the medullary cavity and grows outward thinning
the bony cortex.
The high
prevalence in puberty, the accelerated expansion of lesions during pregnancy,
and the association with precocious puberty in females in the McCune-Albright
syndrome , suggest a hormonal influence that is, so far,
poorly understood. Estrogen and progesterone receptors have been identified in
affected bone.
Patients with
fibrous dysplasia have an accelerated turnover of bone, and many have elevated
serum alkaline phosphatase levels, reflecting increased osteoblastic activity.
Those with extensive disease also have elevated urinary hydroxyproline,
reflecting increased turnover of collagen, a measure of the activity of
osteoclasts. Serum calcium and inorganic phosphorus remain normal, reflecting
compensatory increases in bone formation and resorption. Fibrous dysplasia is
generally considered to occur sporadically. Sassin and Rosenberg found no
positive family histories among 50 cases with cranial fibrous dysplasia. This result is consistent with the current
hypothesis that the disorder results from a somatic mutation early in
embryological development.
Epidemiology and
Risk Factors. The age of onset is variable, but the disorder most
commonly presents in childhood, especially during the period of most rapid bone
TABLE 29-3 -- FREQUENCY OF SKULL BONE
INVOLVEMENT OF SKULL BONE BY FIBROUS DYSPLASIA |
||
Bone |
Number of Cases |
|
(N = 50) |
|
|
Frontal |
28 |
|
Sphenoid |
24 |
|
Frontal
and sphenoid |
18 |
|
Optic
canal involved |
10 (3
bilateral) |
|
Temporal |
8 |
|
Parietal |
6 |
|
Occipital |
2 |
|
Adapted
from Sassin JF, Rosenberg RN: Neurological complications of fibrous dysplasia
of the skull. Arch Neurol 1968;18:363-369. |
|
growth. However, in one series of 50 patients with fibrous dysplasia of the
skull, over half came to medical attention after age 18. There is no difference
in incidence based on race or sex for the most typical forms. However, the McCune-Albright syndrome occurs
more frequently in females. As noted earlier, the bony lesions may expand at an
accelerated rate during pregnancy.
Clinical Features
and Associated Disorders. About 70 percent of patients have the monostotic form
involving a single bone. The remainder have the disseminated polyostotic form,
which is often predominantly unilateral. Sites of involvement vary, the ribs
and long bones being the most common sites. The skull is involved in about 50
percent of polyostotic cases and in 10 to 27 percent of monostotic cases. Most of the clinical manifestations that
prompt neurological evaluation are due to skull involvement ( Table 29-3 ).
Patients may present with a variety of focal neurological findings secondary to
the compressive effects of the involved bone . Visual impairment followed by
hearing loss and tinnitus are the most common presenting neurological deficits.
Although various other cranial neuropathies may occur as a result of the
compressive effects of involved bone, these are rare enough that none were seen
in two large studies of cases involving the skull. , 20 Optic nerve compression with visual
symptoms is common when the frontal and sphenoid bones are involved. A
proptotic and downward displaced eye is often seen when these bones are
involved and should prompt questions about visual symptoms and a radiological
evaluation of the optic canal. Patients with stenosis of the optic canal may
complain of decreased acuity or blurring of vision, scintillating scotoma,
flashing light, or graying of vision when pressure is applied to the globe.
Optic atrophy may be seen on funduscopic examination. The visual symptoms may
be slowly progressive, and they have often been present for some time when the
patient presents. Patients may also have progressive facial asymmetry and
deformity resulting from facial nerve involvement. Patients with hearing
deficits typically have conductive loss due to stenosis of the external canal
and middle ear by the involved temporal bone. A nonthrobbing headache may be a
common complaint as well. Sassin and Rosenberg's patients also had an increased
incidence of seizures (6 of 50), confirming the findings of prior reports. The reason for this association is not known.
Fibrous dysplasia has been
associated with various other disorders. Cutaneous pigmentation occurs in over
50 percent of those with the polyostotic form. The McCune- Albright syndrome
consists of polyostotic fibrous dysplasia, usually largely unilateral, with
cafe(c) au lait spots, and various forms of endocrine hyperfunction, especially
precocious puberty in females. , Rarely, other endocrine abnormalities,
including hyperthyroidism, acromegaly, Cushing's syndrome, hyperparathyroidism,
and diabetes mellitus, may occur. Some patients may have a progressive diffuse
facial deformity called leontiasis ossea; however, this facies may be caused by
other disorders as well, including Paget's disease and craniometaphyseal
dysplasia. Malignant transformation to sarcoma occurs in
about 0.5 percent of patients with fibrous dysplasia and 4 percent of those
with the McCune-Albright syndrome. This tumor is rare in the skull.
Differential
Diagnosis. Fibrous dysplasia must be differentiated from benign
and malignant neoplasms, including meningioma with adjacent hyperostosis,
sarcomas or fibromas replacing bone, bone cysts, and various orbital masses,
including eosinophilic granuloma, Hand-Schuller- Christian disease, and orbital
pseudotumor.
, In addition, other metabolic diseases of bone
must be considered, including Paget's disease, hyperparathyroidism,
hyperostosis frontalis interna, osteopetrosis, and craniometaphyseal dysplasia
(Pyle's disease). In general, age of onset, other clinical features, and
radiological features easily distinguish these disorders. Rarely, the cranial
hyperostosis found in hematological disorders causing bone marrow hyperplasia
or cyanotic heart disease may cause confusion.
Evaluation.
Evaluation should seek to distinguish fibrous dysplasia from other tumors or
metabolic diseases and to assess the presence of deficits that require follow-
up or surgical intervention. Plain x-ray films, CT, and MRI can distinguish
fibrous dysplasia from tumors and characterize other metabolic disorders.
Meningioma with adjacent hyperostosis is distinguishable on CT and MRI by its
typical enhancement and its extension into the cranial cavity. Fibrous
dysplasia expands into the outer table, leaving the inner table and cranial
contents undisturbed. Imaging dedicated to the optic foramina
should be done when the frontal and sphenoid bones are involved. Skeletal
survey and increased uptake on bone scintiscanning can identify asymptomatic
areas of involvement. Serum alkaline phosphatase levels are often elevated, but
serum calcium and inorganic phosphorus are normal, helping to differentiate
hyperparathyroidism. When following patients with frontal and sphenoid
involvement who have not had surgery, photographs of the head, quantitation of
proptosis, documentation of acuity and visual fields, and funduscopic
examinations for optic atrophy should be performed along with radiological
views of the optic canal. These parameters may then be followed every 3 to 6
months until it is clearly established that no progressive visual loss has
occurred. The onset of pain, increasing alkaline phosphatase levels, rapid
growth, or invasion into cortical bone should raise a suspicion of possible
malignant transformation. Biopsy may be needed to distinguish progression of
fibrous dysplasia from malignant transformation.
Management.
Treatment is indicated when clinical function is significantly threatened. When
visual symptoms are present in patients with a small or diminishing optic
canal, surgical decompression by unroofing the optic canal can in most cases
arrest progression. Such treatment rarely leads to significant return of
function; therefore, patients at risk for visual loss must be closely followed.
The lesions are highly vascular, and intraoperative bleeding and intrabony
hematomas may complicate surgery. Radiotherapy is contraindicated because it
greatly increases the risk of malignant transformation. Because lesions may
progress more rapidly during pregnancy, careful follow-up, especially for
visual symptoms, must be maintained. Decisions about surgery during pregnancy
should be based on the neurological status of the patient.
Prognosis and
Future Perspectives. The course in most cases is benign. Leeds and
colleagues followed 15 patients for 6 to 39 years and found that radiological
progression was slight or equivocal in all except two patients. Yet although the lesions become less active
after skeletal maturation, progression does not necessarily stop with bone
growth, and the lesions may reactivate during maturity. Recent success in
elaborating the molecular mechanisms of intracellular signaling and their
alterations in fibrous dysplasia and other diseases opens a rich field in which
our understanding of the pathogenesis of fibrous dysplasia can be deepened. The
elaboration of this work is likely to clarify the endocrinological
manifestations of fibrous dysplasia. A better understanding of the molecular
pathogenesis may eventually produce effective therapies, as it has in Paget's
disease of bone.
Pathogenesis and
Pathophysiology. Paget's disease (osteitis deformans) is a metabolic
bone disease of un known etiology characterized by increased osteoclast size
and activity that results in resorption of bone followed by reactive new bone
formation. This process produces areas of bone resorption with new bone laid
down in an abnormally dense mosaic pattern. The osteoclasts in affected bone
contain nuclear and cytoplasmic virus-like inclusions, and evidence has been
presented of an association with various paramyxoviruses, including measles
virus, respiratory syncytial virus, and canine distemper virus. It has been
speculated that the disorder represents the late effect of viral infection on
osteoclasts or their precursors and that affected osteoclasts tend to form
multinucleated syncytia, which have increased resorptive activity. Normal
osteoblasts may then be stimulated by the primary pathological osteolytic
disorder.
Epidemiology and
Risk Factors. Paget's disease is the second most common metabolic
bone disease in the elderly population, after osteoporosis. It is most common
in patients of northern European ancestry and is uncommon among Asians and
Africans. Males predominate slightly. The prevalence in the elderly population
of the United States is 1 to 3 percent, with 0.1 to 0.2 percent of patients
having significant symptoms. The risk is increased in relatives of those
affected, but pedigrees do not support direct inheritance.
Clinical Features
and Associated Disorders. The disease typically begins in middle age or later
and varies from limited asymptomatic involvement of a single or few sites to
widespread symptomatic disease. The femur, pelvis, and spine are most commonly
affected, although any bone may be involved. Skull involvement is also common.
The most typical presenting symptoms are focal progressive bone pain, deformity
due to expansion of bone, and structural failure such as vertebral compression
fracture or bowing of weight-bearing long bones. Enlarging hat size due to
progressive skull expansion is a classic symptom. Other typical facial changes
include enlarged and coarsened orbits and prognathism. Patients may also notice
focal increases in skin temperature due to increased blood flow at affected
sites. The most common neurological symptoms are headache, deafness, and
problems resulting from spinal disease. The cause of the deafness is unclear.
Both auditory nerve compression and involvement of the middle ear ossicles have
been suggested as mechanisms; however, autopsy studies have not borne out
either hypothesis. , The main mechanisms presumed to cause
neurological symptoms are compression of neural and vascular structures by
overgrowth of bone into limited spaces, traction on neural structures displaced
by bony deformity, and possibly a vascular steal phenomenon resulting from the
local high blood flow demand of pagetic bone ( Table 29-4 ). Involvement of the
skull may cause basilar impression with consequent problems, including
headache, ataxia, hydrocephalus, myelopathy, or cranial neuropathies. Patients
may develop intradiscal lesions with spinal stenosis and, rarely,
extramedullary hematopoiesis. These lesions may cause back pain or may progress
to cause spinal cord and nerve root compression. Yet compressive symptoms due
to spinal disease are uncommon, and when they occur in patients with Paget's
disease, the possibility of sarcomatous degeneration should be considered.
High-output heart failure due to the highly vascular shunts is rare.
TABLE 29-4 -- NEUROLOGICAL COMPLICATIONS OF
PAGET'S DISEASE |
|
Deficit/Localization |
Proposed
Mechanisms of Injury |
Hearing
loss |
|
Conductive |
Involvement
of middle ear ossicles |
Sensorineural |
Compression/traction
of auditory nerve |
Spinal
cord and root involvement |
Compression
of central canal and foramina |
Radiculopathy
(esp. lumbosaeral) |
Compression,
traction |
Myelopathy
(esp. thoracie) |
Compression,
vascular compromise (?steal) |
Cranial
nerves and brain stem |
|
Olfactory
nerve |
Sphenoid
thickening compromising lamina cribosa |
Optic
nerve |
Optic
canal stenosis, orbital compression, ?vascular steal |
Oculomotor
nerves |
Superior
orbital fissure stenosis, ?vascular steal |
Trigeminal
nerve |
Foraminal
compression, ?vascular steal |
Facial
nerve |
Facial
canal stenosis, ?vascular steal |
Lower
cranial nerve, brain stem, cerebellum |
Foraminal
stenosis, basilar impression, platybasia, and vertebral artery compression
from compression within foramina tranversaria |
Major
categories are listed in order of decreasing relative frequency. Among
cranial nerve deficits, those of the lower cranial nerves are most common. |
From 1 to 5.5 percent of patients
with Paget's disease develop osteogenic sarcoma. Other tumors, such as giant cell tumor of
bone, are less common. The pagetic osteogenic sarcoma is osteolytic, and
pathologic fracture is the most common presentation. Malignant degeneration
should also be suspected when a rapid increase in pain or growth is noted or
when compressive spinal findings emerge. About 5 percent of patients have
hyperparathyroidism, but the mechanism of this association is not known. A
complex array of vitamin D-related disorders may also accompany Paget's
disease.
Differential
Diagnosis and Evaluation. The differential diagnosis includes primary and
metastatic bony tumors, especially prostate cancer, and other metabolic bone
disorders that produce lytic lesions and hyperostosis. Degenerative arthritis
may cause confusion, especially when one is trying to determine the source of
symptoms when the two diseases coexist.
Plain radiographs of affected bones
are still the primary means of diagnosis. The bones are expanded, often with
thickening of the cortex. There may be a peripheral edge of lytic fronts and a
small intracortical lytic area. It is common to find lytic lesions
predominating in the skull. The most striking feature is typically
osteosclerosis, which may have a fluffy appearance. The sclerosis is often
intermixed with lytic disease. Uniformly sclerotic ivory vertebrae may be seen.
Radionuclide scanning demonstrates greatly increased uptake and is the most
sensitive test to establish the extent of involvement. Computed tomography can
be used to distinguish osteolytic lesions missed on plain radiographs and can
identify soft tissue masses . In this regard, it may be an important adjunct in
the differentiation of benign lesions from tumor. The urinary
hydroxyproline-creatinine ratio is elevated, reflecting increased bone
resorption. Greatly elevated bone alkaline phosphatase levels reflect increased
osteoblastic activity and are characteristic. The relative elevations of these
values reflect the predominance of either lytic (early) or blastic (late)
disease. Serum calcium is usually normal unless some other factor, such as
immobilization, tips the balance in favor of resorption and hypercalcemia.
Inorganic phosphorus is normal or slightly elevated. When malignant
degeneration is suspected, as in a patient with a pathological fracture, early
biopsy should be pursued.
Management. The
management of Paget's disease has changed in recent years. Both bisphosphonate
and calcitonin attack the underlying metabolic disorder by inhibiting bone
resorption. Although there is no consensus on the best therapy, both are now
being applied to prevent the development of long-term complications.
Etidronate, the first bisphosphonate available, provides definite benefit by
inhibiting osteoclast activity. However, it interferes with the normal
mineralization of new bone. The newer bisphosphonates, such as pamidronate, are
similarly effective without impairing mineralization. These agents may be given
in short courses intravenously or chronically by mouth. The urinary
hydroxyproline level begins to fall within days of an intravenous dose, and the
serum alkaline phosphatase declines later and more gradually. These substances
remain in bone for a long time and may promote prolonged remissions.
Subcutaneous or nasally administered calcitonins also inhibit osteoclasts.
Symptomatic relief follows; however, the effect is short-lived, and the agents
must be continued to maintain this effect. A loss of effect during therapy may
be due to the formation of neutralizing antibodies, which occurs in about one
fourth of those treated. The cytotoxic plicamycin used for hypercalcemia of
malignancy causes a rapid improvement but is more toxic than the
bisphosphonates or calcitonins. Gallium nitrate has antiosteoclastic activity,
but data on its clinical use do not yet support its use outside of controlled
trials. The goals of treatment are to normalize metabolism as evidenced by
biochemical markers and to relieve symptoms. Most patients obtain relief from
bone pain. Reversal of neurological deficits and stabilization--and rarely
improvement--of hearing often follows therapy. There has been radiological
evidence of healing of osteolytic lesions. Malignant lesions should be treated
aggressively with radical resection for best results. Chemotherapy has not yet
been shown to be effective. Early detection is currently the only available way
to improve survival. Patients require life-long surveillance for tumor
recurrence. With the currently available array of effective therapies for
Paget's disease, it is most important that patients be properly referred for
expert care.
Prognosis and
Future Perspectives. Many patients remain asymptomatic. Newer drug
therapies can now address bone pain and other rarer symptoms and may offer
long-term remission. However, as noted previously, prevention or early
detection of neurological deficits is essential to avoid loss of function,
since therapy is more likely to arrest than to reverse them. The prognosis
after malignant degeneration has occurred, however, remains poor, with only
about 10 percent of patients surviving 5 years. Research in Paget's disease has produced
advances in the understanding of the possible underlying etiology, the
metabolic processes that promote the disorder, and the application of several
new therapies. Further clarification of the viral hypothesis, development of
improved diagnostic metabolic markers, and refinement of management with
antiosteoclastic agents are expected in the future.
Numerous other less common
structural disorders are occasionally associated with compressive neurological
signs and symptoms, including hyperostosis frontalis interna, anomalies of the
craniocervical junction, congenital and acquired abnormalities of the spinal
cord, generalized skeletal abnormalities, and such miscellaneous disorders as
arachnoid diverticula. The clinical signs and symptoms of these disorders are
summarized in Table 29-5.
Pathogenesis and
Pathophysiology. The median nerve is subject to compression at the
wrist, where it accompanies the flexor tendons as they pass beneath the volar
carpal ligament. This region, the carpal tunnel, is a closed space within which
pressure may rise. Studies with recording wicks placed in the canal show that
flexion or extension elevate the canal pressure and that thickening of tendon
sheaths or encroachment by other structures leads to a sustained rise in
pressure within the canal. Compression of the median nerve at the wrist
then leads to the carpal tunnel syndrome (CTS), the most common of the
TABLE 29-5 -- OTHER STRUCTURAL DISORDERS
AND ASSOCIATED NEUROLOGICAL SYNDROMES |
|
Disorder |
Neurological
Syndrome |
Hyperostosis
frontalis interna |
Headache |
Anomalies
of the craniocervical junetion region |
|
Basilar
impression |
Brain
stem, cerebellar, and cranial nerve compression |
Chiari malformations |
Brain
stem, cerebellar, and cranial nerve compression |
Atlantoaxial
subluxation (e.g., congenital, rheumatoid arthritis, Down's syndrome) |
Cord and
lower brain stem compression |
Congenital
and acquired abnormalities of the spinal cord |
|
Klippel-Feil
syndrome |
Cord and
root compression |
Scoliosis |
Cord and
root compression |
Kyphosis |
Cord and
root compression |
Generalized
skeletal abnormalities |
|
Achondroplasia |
Spinal
stenosis, disc disease, basilar impression |
Mucopolysaccharidoses |
Cord and
root compression, basilar impression |
Down's
syndrome |
Atlantoaxial
subluxation, basilar impression |
Osteoporosis |
Cord and
root compression |
Osteoporosis |
Brain
stem and cord compression |
Osteomalacia |
Cord and
root compression, basilar impression |
Osteitis
fibrosa cystica (hyperparathyroidism) |
Basilar
impression |
Osteogenesis
imperfecta |
Basilar
impression |
Miscellaneous
disorders |
|
Arachnoid
diverticula |
Cord and
root compression |
entrapment neuropathies. Although nonspecific tenosynovitis is the most common cause of
rising canal pressure, other causes may be relevant: amyloidosis may infiltrate
the tendon sheaths, rheumatoid arthritis may cause synovial tissue to invade
the canal, or hypothyroidism may cause tissue edema.
The median nerve is subject to
compression at proximal sites near the elbow by a hypertrophied pronator teres
muscle, by a vascular anomaly, or by trauma .The symptoms and signs of proximal
median neuropathy differ from those of CTS because the entire median nerve,
including the motor branches to the flexors of fingers and thumb, is affected.
The archetypal motor and sensory
loss anticipated with a lesion of the median nerve at three different levels is
summarizedin Table 29-6 . Not all listed muscles are always affected, and EMG
testing is more sensitive than manual muscle testing.
Epidemiology and
Risk Factors. The degree to which CTS is an occupational disorder
is still disputed. Reported work- and trauma-related disorders
of the upper extremities have increased tenfold in the past two decades,
although only a small proportion relate to CTS. There is no consistent
agreement about the diagnostic criteria, particularly whether the diagnosis
requires confirmation by nerve conduction velocity (NCV) testing. In a Mayo
Clinic retrospective chart review, using both NCV and clinical criteria, the
prevalence of CTS was 125 per 100,000.
It is estimated, based only on
clinical criteria, that half of the cases of CTS seen in the United States are
work- related. Motions of the wrist that require frequent rotation or
flexion-extension, especially with force, seem to produce the highest incidence
of disease. Carpenters, butchers, office workers who use keyboards, dental
assistants, and musicians have a high incidence of CTS. Many workplaces have
made ergonomic redesign a priority because of the rising medical costs of
overuse syndromes, including CTS. Other overuse syndromes include tendinitis,
tenosynovitis, local arthritis, vasospastic conditions due to vibration, and
functional thoracic outlet syndrome. The last of these is discussed
subsequently.
Symptoms of CTS are common in the
latter months of pregnancy, probably because of rising tissue pressures due to
fluid retention. In the majority of instances, the symptoms
TABLE 29-6 -- MEDIAN NERVE COMPRESSION |
|||
Location |
Muscles
Affected |
Action |
Sensory
Loss |
At the
wrist |
Abductor
pollicis |
Abduction |
Palmar
and dorsal surfaces of thumb, index, middle fingers |
Opponens
pollicis |
Opposition |
||
Near
elbow (pronator syndrome) |
Abductor
pollicis |
Abduction |
Palm,
palmar and dorsal surfaces of thumb, index, middle fingers (no loss on
forearm) |
Opponens
pollicis |
Opposition |
||
Pronator
quadratus |
Pronation |
||
Pronator
teres |
Pronation |
||
Flexor
pollicis longus |
Flex
thumb, distal joints |
||
Flexor
digitorum sublimis |
Flex
fingers |
||
Flexor
digitorum profundus |
Flex
fingers, median side |
||
Flexor
carpi ulnaris |
Wrist
flexion |
||
Lumbricals |
Extend MP
joint |
||
Below
elbow |
Flexor
pollicis longus |
Flex
thumb, distal joint |
None |
Flexor
digitorum profundus II |
Flex
index finger, distal joint |
promptly
resolve with delivery. Women are more likely to be diagnosed with CTS than men
by a ratio of 60:40. In patients with occupational CTS, this ratio may be
reversed. The higher frequency in women may reflect smaller wrist
circumference, which correlates with CTS in some studies, or the different work
conditions experienced by women.
Clinical Features
and Associated Disorders. Patients with classic CTS report nocturnal distal
pain and paresthesias. Pain may be present throughout the arm up to the level
of the shoulder, but tingling is typically felt more distally. Some patients
can detect the location of the tingling in the index and middle fingers, but
many find it more difficult. Typically, patients rub and shake the hand because
it feels asleep. On examination, patients in the early stages of disease have
slight weakness of thumb abduction (away from the plane of the palm) and slight
sensory loss, which is sometimes best detected on the dorsum of the index and
middle fingers. There may be paresthesias into the palm with tapping over the
wrist crease (Tinel's sign) and with forced wrist flexion for 30 seconds
(Phalen's sign). In the later stages, patients have visible thenar atrophy and
marked weakness of thumb abduction and opposition. Atypical forms of CTS exist,
and one may observe marked autonomic dysfunction, acute onset, marked sensory
loss, or unexpected neurological findings due to anatomical variations.
Patients with proximal median
neuropathy may have partial or confusing deficits. Often the diagnosis is
suspected because deep palpation over the course of the median nerve is painful
and causes paresthesias.
In about 75 percent of patients, CTS
is accompanied by nonspecific tendinitis in the flexor tendons. Hypothyroidism,
atypical mycobacterial infection, diabetes, rheumatoid arthritis, and
acromegaly are also associated with CTS. Pregnancy accounts for about 1 percent
of CTS cases. In half the patients with symptomatically unilateral CTS, NCV in
the opposite extremity is delayed. Additional ulnar nerve compression, cervical
radiculopathy, bursitis, tendinitis, and osteoarthritis often occur in CTS
patients, as well as an array of rheumatological complaints.
Differential
Diagnosis. Cervical radiculopathy is a common diagnostic issue
when the diagnosis of CTS is under consideration. Patients with radiculopathy
are more likely to report neck pain, radiating pain with coughing or sneezing,
and daytime (as opposed to nocturnal) paresthesias. With C6 or C7
radiculopathy, the biceps or triceps tendon reflex may disappear. Sensory loss
proximal to the wrist is not characteristic of median neuropathy. A theory that
proximal compression of a nerve root will worsen distal entrapment by impairing
axonal transport (the so-called double-crush syndrome) has not been proved. Most investigators believe that in patients
with two sites of compression, for instance, C6 radiculopathy plus CTS, the
disabilities are purely additive.
Large vessel vascular disease,
leading to hemispheric transient ischemic attacks (TIAs), must be considered
because the paresthesias of CTS may be brief enough to suggest TIAs. However,
TIAs are rarely nocturnal and are not painful or unpleasant. Furthermore, hand
tingling in a person with a TIA is usually associated with other neurological signs.
Diffuse peripheral neuropathy is a
diagnostic problem with respect to CTS; it may complicate the
electrophysiological investigation. Diabetic axonal neuropathy is the commonest
coexisting neuropathy.
Evaluation. A
diagnosis of CTS is usually evident from the history, and the neurological
examination should focus on excluding other possible diagnoses. Tinel's and
Phalen's signs are present in about half of patients with CTS and may be
helpful. Electrophysiologic testing is important for the diagnosis of CTS and should be carried out in nearly every
instance prior to surgical release. If the clinical picture is straightforward
and no therapy is planned other than conservative measures,
electrophysiological testing can be omitted. Testing depends on the measurement
of sensory action potentials from median innervated digits, especially the
index finger, and comparison with other sensory potentials in that hand, such
as radial or ulnar. Comparison with the opposite hand is usually done, but the
results are limited by the high frequency of bilateral nerve conduction
abnormalities. In a typical patient with mild CTS, the size of the median
sensory action potential is maintained, but demyelination causes delay when it
is measured at the wrist. In more advanced cases the compound muscle action
potential is also delayed.When the findings are not clear-cut, other
comparisons can be made, and sequential recordings over the nerve as it passes
through the palm can demonstrate the actual site of sensory delay when that is
necessary. EMG recordings from abductor pollicis brevis and comparison with
other intrinsic hand muscles can be made to be certain that only the muscles
innervated by the median nerve are affected; this is especially helpful when
cervical root disease is being considered. There are numerous pitfalls provided
by anatomic variations, such as the Martin-Gruber anastomosis, in which nerve
fibers destined to innervate the thenar muscles are found in the median nerve
at the elbow but join the ulnar nerve in the forearm and pass the wrist in the
ulnar nerve, giving the electrophysiological appearance of a marked loss of
motor potential with stimulation of the median at the wrist. When median
neuropathy near the elbow is being considered, the EMG pattern is most helpful
because nerve conduction tests show diagnostic changes in no more than a third
of cases.
Management. Many
patients with CTS are managed successfully by conservative means, with reduction of any activity that may
exacerbate tenosynovitis, use of a wrist splint, and oral nonsteroidal
anti-inflammatory drugs (NSAIDs), such as ibuprofen 1600 mg/day or naproxen 750
mg/day. The splint should hold the wrist in a few degrees of extension and may be worn at night or during wrist use.
Prolonged or continued wrist splint use may lead to reduced range of motion and
should be discouraged.
Steroid injection within the carpal
canal is a time-honored technique and may be helpful diagnostically. After
local anesthesia of skin and subcutaneous tissue, 15 to 30 mg of a depot
preparation of methyl prednisolone is injected. The needle should be introduced
2 to 3 cm proximal to the palm itself and to the ulnar side of the palmaris
longus tendon; injection into the nerve is to be avoided. No more than three
injections should be done, since damage to the tendons may occur with frequent
use of local steroids. Injection may provide relief of symptoms for several
months, but symptoms recur in over 80 percent of patients. Injection is
particularly suitable for pregnancy-related CTS.
Patients who have persistent
symptoms following conservative management should be referred for surgical
release, and those with sensory or motor deficits normally require surgery.
Advanced disease, especially in the elderly, will not improve motorically, so
the only reason for surgery is to provide relief from pain. The degree of
slowing of NCV is not a good predictor either of the need for surgery nor for
outcome. The results of surgery are generally excellent. Forty percent of
patients are asymptomatic following surgery, and another 40 percent have only
trivial residual symptoms. Long-lasting incisional pain, slight weakness of the
wrist, and a small number of patients who are neurologically worse after
surgery are found in 10 percent of surgical outcome studies.
Prognosis and
Future Perspectives. In general, the prognosis for CTS is good. The
condition is not disabling unless there are compounding problems such as
compensation issues, psychological impairment, reflex sympathetic dystrophy, or
an occupation requiring great strength or precise control of the digits (as in
instrumental musicians).
Surgical techniques are under
constant review and modification. Several procedures for endoscopic carpal
tunnel release have been introduced. Overall, these seem to have efficacy that
is about equal to that achieved with standard release procedures, as judged by
randomized trials reported thus far. There have been reports of hemorrhage within
the palm, ulnar nerve compromise, and other complications that do not occur
with standard release. The endoscopic procedure needs further evaluation.
In many industries, major efforts
have been made to avoid the risk of occupational CTS, along with other overuse
syndromes, by undertaking ergonomic redesign of work stations and tools. These
efforts will continue in the future, since the economic consequences of these
conditions can be very severe. In fact, within the last 2 years, premiums for
worker compensation insurance have fallen slightly in many parts of the United
States, possibly signaling a change in incidence of overuse and CTS in the
workplace.
Pathogenesis and
Pathophysiology. The ulnar nerve is subject to entrapment at the elbow
and, less commonly, can be traumatized in the palm or at the wrist. The common
site of compression is at the cubital tunnel, which consists of the edge of
aponeurosis of the flexor muscles, beneath which the nerve must pass . This
area is located about 3 to 5 cm distal to the medial epicondyle. Compression
within the cubital tunnel is increased by elbow flexion. Less commonly, the
nerve can be compressed externally at the elbow groove (for instance, during
anesthesia), or by synovium in rheumatoid arthritis patients, or by callus
following a fracture.
Epidemiology and
Risk Factors. The prevalence of ulnar nerve disorders is unknown.
Based on the apparent frequency of abnormalities in routine EMG/NCV studies,
asymptomatic or minimally symptomatic ulnar neuropathy is very common,
approaching the range of incidence of CTS.
Risk factors for ulnar neuropathy
are poorly defined. Arthritis of the elbow may be a contributing cause. Persons
who habitually rest the flexed elbow on a table or chair, specifically those
with chronic pulmonary disease, can compress the nerve. There is a much lower
incidence of ulnar neuropathy as an occupational disorder compared with CTS,
but musicians who use one arm in a flexed position (cellists, violinists)
commonly develop ulnar neuropathy. In baseball pitchers, particularly those who
employ the slider and curve ball pitch are more at risk than fast ball
pitchers. Other than these exposures, ulnar neuropathy is more common in the
nondominant side, suggesting that repeated elbow flexion is more important
etiologically than is repeated muscular usage. Ulnar neuropathy at the elbow is
the most common anesthesia-related compressive neuropathy.
Ulnar neuropathy at the wrist can be
caused by ulnar artery thrombosis at that site, by lacerations or ganglia. The
ulnar nerve lies outside the carpal tunnel adjacent to the ulnar artery. The
first occupational focal neuropathy described was observed by Ramsay Hunt, who
reported compression of the ulnar nerve at the wrist in telegraph operators,
who used the proximal palm to tap the key.
Clinical Features
and Associated Disorders. The first symptoms in the majority of patients with
cubital tunnel syndrome involve intermittent hypesthesia in the ulnar
distribution. This is often associated with elbow flexion and dissipates with
elbow extension. These symptoms may vary during the day and from day to day,
disappearing for a period of time. Pain around the elbow, tenderness over the
cubital tunnel, or radiating pain traveling into the palm may also be present.
The amount of pain and paresthesia vary, and for some individuals the sensory
loss is not bothersome. Although most patients present with sensory complaints,
motor dysfunction, including weakness of intrinsic hand muscles and decreased
grasp or pinch, or a loss of dexterity, can occur. An early motor symptom can
include a loss of control of the fifth digit due to weakness of the third
palmar interosseous muscle. In other patients, no early symptoms are noted, and
the patient eventually presents with marked muscular atrophy and weakness. (See
Table 29-7 for individual muscles and sensory distribution.)
Diabetes mellitus may be a comorbid
illness and seems to predispose to ulnar neuropathy, possibly by impairing the
microvasculature of the nerve. Rheumatoid arthritis may cause synovial
overgrowth and compress the ulnar nerve.
Differential
Diagnosis. Neurogenic thoracic outlet syndrome, due to an
aberrant ligament or band compressing the inferior trunk of the brachial
plexus, is described later. The clinical findings may resemble those of ulnar
neuropathy. This entity can be detected by finding weakness in median
innervated muscles as well as ulnar innervated muscles and by the presence of
sensory loss on the medial forearm. The same anatomical features pertain to
metastases or a primary tumor within the brachial plexus or to radiation
plexopathy. Cervical spondylosis affecting the C8 nerve root is quite rare;
most radiculopathies affect the C6 or C7 root. Symptomatic thoracic outlet
syndrome, in which the plexus is compressed by elevated arm positions or by
muscular spasm, does not cause sustained neurological abnormalities.
Evaluation. The
sensory examination is important, particularly in cases of early disease, in
which sensory abnormalities may be the only findings. Sensory loss with ulnar
neuropathy typically stops at the wrist creases. If the ulnar neuropathy is at
the level of the wrist, the dorsum of the hand will be spared. Clinical
evaluation should include a careful study of the pattern of weakness. Ulnar
neuropathy causes weakness of adduction and abduction of all fingers, and
adduction of the thumb. Importantly, flexion of the terminal phalanx of the
fifth (or fourth and fifth) digit is carried out by the flexor digitorum
profundus IV and V, a muscle that is located in the forearm. If this is the
only flexor found weak, cubital tunnel syndrome is very likely.
With lesions of the ulnar nerve
above and at the elbow, there can be atrophy and flattening of the hypothenar
eminence and interossei. The hand may demonstrate a "claw-hand"
deformity (main en griffe), with the fifth, fourth, and, to a lesser
degree, the third fingers hyperextended at the metacarpophalangeal joints and
flexed at the interphalangeal joints. The hyperextension at the
metacarpophalangeal joints results from paralysis of the interossei and ulnar
lumbricals. This results in the unopposed action of the long finger extensors;
the flexion at the interphalangeal joints is due to tension from the long
finger tendons. Ulnar paresis or paralysis also affects extension at the
interphalangeal joints of the second to fifth fingers, adduction and abduction
of the second to fifth fingers, and abduction and opposition of the fifth
finger. Froment's prehensile thumb sign (signe du journal) may be
present as a result of adductor pollicis weakness. This sign occurs when a
sheet of paper, grasped between the thumb and index finger, is pulled; the
proximal phalanx of the thumb is extended, and the distal phalanx is flexed.
Electrophysiological testing focuses
on the demonstration of slowing of motor and sensory fibers at the elbow. Sometimes it is possible to show that only
the ulnar nerve is affected but not to localize the disorder well. This happens
particularly when there is significant axonal loss in patients with
long-standing neuropathies.
Management.
Conservative management consists of reducing occupational exposure, if any,
using NSAIDs, and using a half-splint held in place with a wrap, so that the
elbow is maintained in gentle extension. Such a splint can be worn at night as
well as during the day. Steroid
injections
TABLE 29-7 -- ULNAR NERVE COMPRESSION |
|||
Location |
Muscles
Affected |
Action |
Sensory
Loss |
At elbow
(cubital tunnel syndrome) |
Flexor
digitorum profundus V |
Flexes
little finger, distal joint |
Medial
side of hand and fingers to wrist crease |
Interossei |
Adducts
and abducts |
||
Flexor
pollicis brevis |
Adducts
thumbs |
||
Opponens
V |
Adducts
little finger |
||
At wrist |
Interossei |
Adducts
and abducts |
Palmar
and medial hand and finger |
Flexor
pollicis brevis |
Adducts
thumb |
||
Opponens
V |
Adducts
little finger |
have no role in the treatment of patients with the cubital tunnel syndrome.
The decision to refer patients for
surgery should be based chiefly on the presence of a demonstrated worsening
deficit, even if mild. Many ulnar neuropathies stabilize and remain
mild. Pain may be a significant problem and may force an early decision for
surgery. The choice of a procedure is not without controversy. Many surgeons
prefer a simple cubital tunnel release, by sectioning the taut aponeurosis.
Others remove the medial epicondyle, which forms the medial wall of the ulnar
groove, in order to decompress the nerve. Mobilization of the nerve and moving
it to a position above the epicondyle and beneath the flexor muscles produces a
definitive decompression. Attention to arm position during anesthesia will help
to cut down on perioperative neuropathy. In many patients the condition
stabilizes at a mild or moderate degree of nerve dysfunction.
The radial nerve is subject to
compression at several sites ( Table 29-8 ). An acute compression can occur at distal
parts of the brachial plexus, in which the nerve is compressed against the
humerus, usually when the patient falls asleep with the arm draped over a
chair; this is the so-called Saturday night palsy. Fractures involving the
shaft of the humerus can damage the nerve, since it is closely applied to the
bone through much of its course. There is a radial tunnel located beneath the
extensor carpi radialis, 3 to 4 cm distal to the lateral epicondyle. Finally,
the radial sensory branch, supplying the dorsum of the wrist and hand, is
subject to laceration or contusion .
Persons subject to acute intoxication
from alcohol or drugs are those most likely to develop an acute radial nerve
compression. The radial tunnel syndrome is usually chronic and is associated
with anatomical variations near the elbow that have no predictable risk
factors.
Radial nerve palsy causes wrist drop
with paralysis of finger and thumb extension. Because the intrinsic hand
muscles are weak in this position, apparent palsy of finger abduction is seen;
this can be corrected by supporting the fingers. In patients with acute
Saturday night palsy, the brachioradialis is weak, but the triceps muscle is
usually only partially affected. Sensory loss is usually slight. The radial
tunnel syndrome affects the posterior interosseous nerve, so that wrist
extension can be spared because the extensor carpi radialis is above the level
of the compression. Local pain and a Tinel's sign at the site of the radial
tunnel help to identify this uncommon syndrome.
Radial tunnel syndrome can resemble
the signs of a C7 radiculopathy, but the weakness of the finger flexor muscles
seen with the C7 deficit soon leads to correct localization. Acute radial palsy
is usually painless, but the pattern of weakness, including pseudo-weakness of
intrinsics, is readily recognizable. Focal motor neuropathy, which is probably
a variant of chronic inflammatory neuropathy, often affects the radial nerve at
the region of the elbow; usually other nerves are affected too. Radiological
studies are usually not required. If there is a question of hematoma or
fracture, plain films or ultrasound examination will suffice.
TABLE 29-8 -- RADIAL NERVE COMPRESSION |
|||
Location |
Muscles
Affected |
Action |
Sensory
Loss |
At elbow
(posterior interosseus syndrome) |
Extensor
carpi ulnaris |
Extends
wrist |
None |
Extensor
digitorum communis |
Extends
fingers |
||
Extensor
pollicis |
Extends
thumb |
||
Abductor
pollicis |
Extends,
abducts |
||
Below
elbow (sensory radial branch) |
None |
|
Lateral
side of forearm and hand |
If nerve conduction studies are carried out acutely, they will show conduction
block because the acute disorders are demyelinative in most instances.
Electromyographical studies in patients with radial tunnel syndrome can be very
helpful in locating the exact site of nerve compression.
If an acute radial palsy lasts for
more than a few days, the patient should be referred for physiotherapy and for
occupational therapy to allow fitting of a spring-loaded brace for finger and
wrist extension. Radial tunnel syndrome patients may require surgical
exploration; the two indications for surgery are pain and established or
progressing weakness. Acute radial palsy patients usually recover
completely within 4 to 6 weeks. Even after severe injury to the nerve, full
late recovery can occur. With bracing, acceptable use of the hand can be
maintained.
True neurogenic thoracic outlet
syndrome (TOS) is due to an aberrant band or ligament crossing the brachial
plexus, usually between the transverse process of the C7 vertebra and the
sternum or first or second rib. The inferior trunk of the plexus, consisting of
fibers derived from C8 and T1 nerve roots, is compressed. The syndrome is very
rare. Symptomatic, or secondary, TOS does not
involve an identifiable anatomical structure causing nerve compression and is
believed to be due to an abnormal shoulder posture or to muscle spasm. It is
most often diagnosed with certainty in persons who use one or both arms above
the head or in instrumental musicians. Sometimes there is a preceding history
of minor cervical or shoulder trauma precipitating muscle spasm or a change in
shoulder or neck posture. Some patients are tall, slender, and more round-
shouldered than average ("droopy shoulder syndrome"). In addition,
vascular types of compression can occur within the thoracic outlet, usually
affecting the subclavian artery. Surprisingly, neurogenic and vascular
compression do not usually coexist, most patients demonstrating one pattern or
the other, but not both. There are no known risk factors for vascular TOS.
Since some patients develop thrombosis of the subclavian or innominate artery,
a thrombotic disorder would be a risk factor.
The diagnosis of true neurogenic TOS
requires an anatomical abnormality, which is presumably congenital. Symptomatic
TOS may be occupational. There may be an overlap with overuse syndrome or with
other nerve entrapments, and if the clinical findings are slight, a firm
diagnosis may not be possible. True neurogenic TOS causes a stereotyped
clinical picture. Patients complain of numbness and pain in the affected arm.
There is weakness of all intrinsic muscles of the hand, corresponding to the C8
and T1 myotomes, and often starting with the thenar muscles. Sensory loss, if
present, is located on the ulnar side of the hand and forearm. With further
compression of the plexus, extensors of the thumb and index finger and pronator
quadratus are affected.
Symptomatic TOS causes positional
numbness and pain without demonstrable neurological deficit. There may be pain
on palpation over muscles or nerve trunks. The radial pulse may diminish with
arm abduction, but the value of this observation is much reduced by the fact
that it is present in 15 percent of normals.
Alternative diagnoses center around
other conditions that affect the lower plexus. These include metastatic cancer,
radiation injury, syringomyelia, and, rarely, lower cervical disc herniations.
Nerve conduction testing is important, mainly to exclude atypical median or
ulnar neuropathies. The plexus injury in true neurogenic TOS is axonal in type,
so that reductions in ulnar sensory action potentials, accompanied by EMG
findings in the C8 and T1 myotomes, are to be expected. An MRI scan of the
plexus and cervical spine is advisable to exclude tumor. Many tests of pulse
volume in various arm positions have been described in the past, but they have
little role in modern medicine. If there is a suspicion of subclavian stenosis
or occlusion, angiography or MR angiography should be carried out without
delay.
Symptomatic TOS is treated by
physiotherapy, consisting of a program to strengthen the muscles and improve
cervical and periscapular strength and posture. Neurogenic TOS may require
surgical release; for proper visualization, a retroclavicular approach is best,
although an extensive literature describes transaxillary first rib removal, an
unproven procedure that has many described complications. The prognosis of patients with symptomatic
TOS depends on proper management through physiotherapy. The prognosis of those
with neurogenic TOS is unknown owing to the marked rarity of the disorder.
The sciatic nerve and its branches
are resistant to entrapment, and there is no consistent area in the lower
extremity where entrapment occurs. Compression of the sciatic nerve can occur
in situations in which there is variation in the course of the sciatic nerve
between parts of the piriformis muscle, or by a myofascial band in the distal
portion of the thigh between the biceps femoris and the abductor magnus. The
sciatic nerve can be acutely compressed or injured by retroperitoneal bleeding
in the setting of anticoagulant therapy. Surgical trauma from hip replacement,
gunshot wounds, fractures of the hip or femur, and infarction are some of the causes
of sciatic nerve lesions. Such compression may occur following fractures or
other acute traumatic lesions. Forcible inversion of the foot, which results in
stretching of the nerve and damage at the level of the fibular head, may cause
peroneal dysfunction. Other causes of peroneal damage include improperly
applied casts or tight garters, bandages, or stockings. Some patients may be
susceptible to peroneal compression including those who were unconscious from
drugs, anesthesia, or illness with coma. Excessive weight loss in the presence
of chronic illness may also predispose the patient to peroneal compression.
Certain occupations including those that require prolonged sitting, squatting,
or kneeling may provoke peroneal dysfunction. Finally, ganglia or tumors of the
nerve or neighboring structures may be associated with compression of the
peroneal nerve. Tibial nerve dysfunction resulting from tarsal tunnel syndrome
consists of entrapment of the posterior tibial nerve at the level of the medial
malleolus. This syndrome is quite rare and usually occurs after ankle fracture
or in patients with rheumatoid arthritis. Any or all of these divisions of the
posterior tibial nerve may be affected.
The risk factors for peroneal or
sciatic mononeuropathy are those associated with any acute compression, namely,
local trauma, fracture, or prolonged unconsciousness. Peroneal nerve
compression can occur with prolonged squatting and has been seen in vegetable
or fruit pickers working in fields.
Diabetes is a risk factor for
sciatic or peroneal neuropathy, probably because it contributes to vascular
insufficiency and predisposes to nerve infarction or conduction failure if the
nerve is compressed.
The sciatic nerve innervates the
knee flexors and all the muscles below the knee. Therefore, complete palsy of
the sciatic nerve leads to marked instability of the foot and to a severe
impairment of gait. A complete palsy of the sciatic nerve is extremely rare and
would not be expected from sciatic nerve entrapment. The entire foot except for
a small region supplied by the saphenous nerve over the medial malleolus is
supplied by the sciatic nerve. With entrapment, pain or paresthesia may radiate
into these territories.
Peroneal palsy is usually acute and
is the result of external pressure applied to the nerve in its vulnerable fixed
position against the fibula. Loss of eversion (if the superficial division is
involved) or of dorsiflexion of the toes and ankle (if the deep division), or
both, are found. Sensory loss is much more apparent with lesions of the
superficial division, and such loss involves the lateral calf, the lateral
malleolus, the dorsum of the foot, and the medial three or four toes up to the
interphalangeal joint. With lesions of the deep division, the sensory loss is
smaller and involves the small area between the first and second toes and the
web space and the adjacent portion of the dorsum of the foot. In common acute
compressive peroneal lesions, pain is not a typical complaint, and there are
few or no sensory symptoms. With entrapment or chronic lesions, patients may
experience radiating pain and slowly progressive motor and sensory
disturbances.
The primary symptom of tarsal tunnel
syndrome is a burning, unpleasant pain in the sole of the foot. This pain may
become worse during rest or while sleeping at night. Pain and sensory
disturbances over the entire plantar surface of the foot may occur. With
involvement of one or two divisions of the posterior tibial nerve, these
findings may be restricted to only a portion of the plantar surface.
Lesions of the sciatic nerve must be
distinguished from herniated lumbar disc disease. Most patients with sciatic
pain due to lumbar disc disease have monoradicular symptoms. Thus, pain
radiating to the lateral side of the foot and small toe is associated with S1
lesions; pain radiating to the dorsum of the foot with L5 lesions; and pain
radiating to the medial part of the calf with L4 lesions. Marked weakness of
both the anterior tibial and gastrocnemius muscles suggests sciatic neuropathy.
Other disorders to be considered in the clinical setting of sciatic nerve
dysfunction include lumbar spinal stenosis (see earlier discussion) and
vascular (diabetic) neuropathy . In patients with progressive sciatic deficits
with pain as the initial symptom, intraspinal carcinoma, lymphoma, and myeloma
should be included in the differential diagnosis.
L5 radiculopathy may resemble
peroneal dysfunction, yet in most patients there is accompanying back pain or
sciatic pain. In these cases, weakness of both eversion and inversion and the
loss of sensation above the midpoint of the calf of the outer surface, together
with the greater weakness of the extensor hallucis than of the anterior tibial
muscle, suggest an L5 radiculopathy.
In distinguishing tarsal tunnel
syndrome from other disorders, the examiner should consider the varied causes
of foot pain. These include plantar fasciitis, stress fractures, bursitis, and
trauma to the plantar nerve distal to the tarsal tunnel. Diabetic neuropathy
causing burning painful feet may also be difficult to distinguish from
bilateral tarsal tunnel syndrome.
Electromyography and NCV testing are
very helpful in the diagnosis of disorders of the sciatic nerve and its
branches. Focal slowing at the fibular head, implying a
demyelinating process, is usually found in patients with acute or chronic
peroneal mononeuropathies. Sometimes in those with severe lesions, there is
enough axon loss to obscure this important finding. Many sciatic lesions of
diverse causes result in marked axon loss, and no demonstrable area of focal
slowing will be found even though the lesion is anatomically focal. In these
situations, reliance on the pattern of EMG abnormality is still very helpful.
Computed tomography or MRI scanning of the lumbar spine, the retroperitoneal
space, and the course of the nerve may be needed to establish an exact
anatomical diagnosis. Spontaneously arising and progressive mononeuropathy in
the lower extremity always presents the possibility of unrecognized tumor.
Management of these lesions depends
entirely on their cause. Pain control with sciatic lesions is best achieved by
pharmacological means. In patients with peroneal palsy, a fitted brace (ankle
foot orthosis AFO ) should be used to
protect against ankle joint damage and improve gait unless the muscle paresis
is mild. Even in patients with acute lesions, the prognosis of sciatic or
peroneal neuropathy is at best, fair. Too often there is extensive axon loss
and a resulting lasting deficit.
There are other uncommon compressive
neuropathies of the lower extremities including those involving the femoral,
TABLE 29-9 -- OTHER NERVES IN THE LOWER
EXTREMITY AND ASSOCIATED COMPRESSIVE SYNDROMES |
|||||
Nerve |
Muscles
Affected |
Reflex
Changes |
Sensory
Loss |
Compressive
Causes |
Etiological
and Anatomic Differential Diagnosis |
Femoral |
Hip
flexors |
Reduced
knee reflex |
Anterior
thigh, medial ealf |
Idiopathic,
iatrogenic by surgery, retroperitoneal, hemorrhage, tumor |
Infarction
trauma radiculopathies |
Knee
extensors |
|||||
Lateral
femoral cutaneous |
None |
None |
Lateral
thigh |
Entrapment |
|
Saphenous,
ilioinguinal and iliohypogastric |
None |
None |
Medial
calf, low abdomen |
Iatrogenic
surgery, scar after surgery |
Trauma,
infarction |
None |
None |
||||
Obturator |
Thigh
adductors |
None |
Medial
thigh (smal1 area) |
Pelvic
tumor, hematoma |
Trauma |
Interdigital
nerve (Morton's neuroma) |
|
|
|
Head of
fourth metatarsal |
Trauma |
lateral femoral cutaneous, saphenous, ilioinguinal-iliohypogastric, and
obturator nerves. The clinical syndromes and common causes are reviewed in Table
29-9 .