The Value of Somatosensory- and Motor-Evoked Potentials in Predicting and Monitoring the Effect of Therapy in Spondylotic Cervical Myelopathy

STUDY DESIGN: A 2-year follow-up prospective randomized electrophysiologic and clinical study of patients with spondylotic cervical myelopathy. OBJECTIVE: To assess the value of somatosensory- and motor-evoked potentials in the evaluation and prediction of the effect of therapy. SUMMARY OF BACKGROUND DATA: Previous studies have yielded conflicting data concerning the correlation between the changes in evoked potential parameters and the clinical postsurgical outcome in spondylotic cervical myelopathy. METHODS: Sixty-one patients with magnetic resonance images suggesting spondylotic cervical cord compression and clinical signs of cervical myelopathy were divided into two groups according to the degree of clinical cervical cord involvement. The 49 patients with mild and moderate spondylotic cervical myelopathy were randomized into groups that underwent either surgical or conservative therapy. Patients were evaluated clinically and by the means of somatosensory- and motor-evoked potentials. RESULTS: The clinical and evoked potential changes showed good correlation on the group level, but poor correlation intraindividually. There were no significant evoked potential and clinical group changes after 6 months and 2 years in the mild myelopathy group treated either surgically and conservatively, whereas patients with severe myelopathy displayed significant improvement in clinical and evoked potential parameters after surgery. In a subgroup of patients, the isolated segmental medullar N13 abnormality could potentially predict favorable postsurgical clinical outcome. CONCLUSIONS: Longitudinal evoked potentials showed limited use for evaluating the results of therapy in an individual patient. They could be useful in the group assessment of therapy results and in labeling a subgroup of patients with potentially favorable postsurgical outcome.