Neurogenic motor evoked-potential monitoring in anterior cervical surgery

A prospective evaluation of a consecutive series of patients undergoing anterior cervical surgery monitored by the neurogenic motor evoked-potential technique. To evaluate the efficacy of neurogenic motor evoked-potential (NMEP) monitoring and its ability to predict clinical outcome in anterior cervical surgery. Forty-nine consecutive patients undergoing anterior cervical surgery were monitored using NMEP technique and were followed prospectively. Latency and amplitude data from the median and ulnar nerves were recorded and evaluated at baseline and at closure. Because existing injury or needle placement may affect absolute values, ratios of the data from both sides were used. All patients had their data evaluated for detection of intraoperative neurological injury. Thirty-eight patients had a monoradiculopathy on presentation and were followed for > 1 year and had either a good or excellent clinical result by the Odom criteria. The NMEP data from these patients were evaluated using the paired Student's test, looking for improvement during surgery. No patient had diminution of NMEP data nor a worsening or new neurological deficit. In patients with symptoms < 1 year before surgery, significant improvement was seen in the ipsilateral median nerve ratios (p = 0.05). No statistically significant results were seen in the ulnar nerve latencies or in the amplitude from either nerve. In patients with symptoms > 1 year, no statistically significant improvement was seen in any parameters. NMEP monitoring of anterior cervical surgery is a promising technique, allowing evaluation of the motor tracts. Duration of symptoms affects NMEP results. Intraoperative improvement of NMEP data after decompression may predict improved clinical outcome.