Motor evoked potentials in the post-surgical follow-up of cervical spondylotic myelopathy.

Eighteen patients (6 female, 12 male; average age 51 years, range 37-79) with clinical and radiological evidence (MRI) of cervical spondylotic myelopathy (CSM) were examined. The subjects were divided into two groups depending on whether radiology indicated single level (9 patients) or multilevel (9 patients) compression of the cervical cord. All of the patients underwent surgical decompression. Seriate exam with trans-cranial magnetic stimulation was performed in double session before surgery, and 3 and 12 months after surgery. The follow-up study of these patients revealed a statistically significant neurophysiological improvement only in those patients with single-level compression. In these cases, the cervical cord pathology revealed by MRI signal hyperintensity in T2 may at least partially consist of an edematous component and/or an initial demyelinization that has still a chance of recovery. In patients with multilevel damage, the compression may cause irreversible lesions.