Cervical spondylotic myelopathy: a review of surgical indications and decision making.

Cervical spondylotic myelopathy (CSM) is frequently underdiagnosed and undertreated. The key to the initial diagnosis is a careful neurologic examination. The physical findings may be subtle, thus a high index of suspicion is helpful. Poor prognostic indicators and, therefore, absolute indications for surgery are: 1. Progression of signs and symptoms. 2. Presence of myelopathy for six months or longer. 3. Compression ratio approaching 0.4 or transverse area of the spinal cord of 40 square millimeters or less. Improvement is unusual with nonoperative treatment and almost all patients progressively worsen. Surgical intervention is the most predictable way to prevent neurologic deterioration. The recommended decompression is anterior when there is anterior compression at one or two levels and no significant developmental narrowing of the canal. For compression at more than two levels, developmental narrowing of the canal, posterior compression, and ossification of the posterior longitudinal ligament, we recommend posterior decompression. In order for posterior decompression to be effective there must be lordosis of the cervical spine. If kyphosis is present, anterior decompression is needed. Kyphosis associated with a developmentally narrow canal or posterior compression may require combined anterior and posterior approaches. Fusion is required for instability.