Page 705 - Motor Disorders Third Edition

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Other shortcomings of MRI include reduced detail of bony
structures, inability to clearly delineate soft disc from osteo-
phytic spurs, and the exaggeration of cord compression by
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studies employing needle electromyography (EMG) are of
particular value in assessing concomitant cervical polyra-
diculopathy, the abnormal findings of which were associ-
ated with later development of symptomatic CSM (30).
TREATMENT
The natural history of CSM (30) is variable with many
patients experiencing a slow, stepwise decline, while long
periods of quiescence are not uncommon. CSM of several
years duration is associated with pathological progression
of CSM, associated with marked atrophy, neuronal loss in
spinal gray matter, and severe degeneration in the white
matter columns, similar to that seen in hypoperfusion (12,
19, 31). Gray matter infarction and cavitation is associ-
ated with white matter demyelination in affected patients
(12). An anteroposterior compression ratio of up to 40%
of normal was associated with flattening of the gray mat-
ter with mild demyelination at postmortem examination
(12). With further progression of indices of anatomic com-
pression there was a further deterioration, from gray mat-
ter cavitation and white matter demyelination to extensive
gray matter necrosis with white matter gliosis. Clinically
objective measurable deterioration rarely occurred in sub-
jects younger than 75 years of age, some of whom actually
improved (32, 33). In this cohort, non-operative manage-
ment is assured by a stable clinical course over 36 months,
and functional measures of the modified Japanese Ortho-
paedic Association (mJOA) scale score, 10-meter walk
time, and video-recorded performance of activities of daily
living (ADL) do not worsen over time (30).
Conservative management includes various methods
aimed at immobilization of the cervical spine to reduce the
excessive motion thought to contribute to CSM. Immobiliza-
tion devices used include the soft cervical collar, Philadelphia
collar, and Minerva jacket. Physical therapy and nonsteroi-
dal anti-inflammatory drugs have also been used. The high
rate of noncompliance with immobilization therapy and the
inability of many devices to effectively immobilize the spine
have cast doubt on the validity of conservative therapy. The
results of conservative trials have been mixed, with reported
improvement rates of up to 55% (14, 21). These reports of
stabilization of symptoms with conservative therapy should
be considered in light of the natural history of CSM, which
may stabilize without intervention in certain instances.
CERVICAL SPONDYLOTIC MYELOPATHY / 687
Historically, the most widely used surgical treatment for
CSM consisted primarily of posterior decompression via
laminectomy (34, 35). This entails removal of the lamina,
spinous processes, medial facet joints, and ligamentum
flavum. Modifications were subsequently described that
included sectioning of the dentate ligament, decompression
of nerve roots by foraminotomies, and removal of anterior
osteophytes. The aim was to safely remove as much of the
compressive pathology as possible, allowing the cord to
expand posteriorly. Posterior laminectomy has the primary
advantage of relative ease of performance. The wide visual-
ization of the nerve roots and cord allows direct assessment
of adequacy of decompression. It is indicated in patients
with posteriorly located compressive elements, those with
exaggerated cervical lordosis that accentuates draping of
the cord over posterior elements, and patients with con-
genital cervical stenosis. The posterior approach also allows
multiple segments to be decompressed without need for
complicated reconstruction procedures. In general, the
disadvantages of the posterior approach include inabil-
ity to adequately treat anterior compression when it is the
predominating pathologic process. Another serious prob-
lem is destabilization of the cervical spine that may occur
after extensive laminectomies. Utilization of lateral mass
plates for fusion of decompressed levels provides adequate
postoperative stabilization, especially in those with radio-
graphic evidence of subluxation. Some patients may dete-
riorate after posterior decompression due to dorsal kinking
of the cord after inadequate decompression in the presence
of prominent ventral osteophytes. Postoperative scar for-
mation can cause further compression. Many variants of
laminoplasty with preservation and hinging of posterior
elements have been proposed to remedy this problem, but
results have been equivocal (36). There is no evidence at
present to suggest that laminoplasty is superior to laminec-
tomy and arthrodesis or laminectomy alone (37).
A variety of anterior surgical techniques have improved
functional outcomes after surgical treatment for CSM,
including anterior cervical discectomy with fusion (ACDF),
anterior cervical corpectomy with fusion (ACCF), lamino-
plasty, laminectomy, and laminectomy with fusion (37).
ACDF and ACCF yielded similar results in multilevel spine
decompression for lesions at the disc level with comparative
rates of improvement of 60% and 55% (38, 39). Historically,
a traditional anterior approach (35, 40) entailed resection of
the median portion of vertebral body at the most severely
compressed levels, along with resection of intervertebral
discs and osteophytes. It had the clear advantage of directly
decompressing the anterior cord, the most common site of
significant compressive pathology in CSM. An ACDF pro-
cedure is employed in those undergoing multilevel anterior
cervical spine decompression for lesions located at the disc
level. It is indicated in those with normal cervical curvature,