Continuous intraoperative electromyographic and transcranial motor evoked potential recordings in spinal stenosis surgery

Abstract

Spinal stenosis refers to narrowing of the spinal canal with encroachment of the neural structures by adjacent bone and soft tissue. Surgical treatment usually offers greater pain relief and functional recovery than non-surgical treatment. Nevertheless, neurological complications from decompressive laminectomy have been reported to range between 1% and 33%. Therefore, the purpose of this prospective study was to evaluate the efficacy of transcranial motor evoked potentials (TcMEP) and continuous electromyography (EMG) to prevent irreversible pyramidal tract damage during decompressive laminectomy. We prospectively evaluated 25 patients (11 males and 14 females) who underwent decompressive laminectomy for lumbar spinal stenosis. TcMEP and EMG were monitored intraoperatively. Postoperatively all patients had regular follow-up examinations. Electrophysiological monitoring was not performed in two patients because of the use of incompatible anaesthetic regimens. In 17/25 patients there was an increase in TcMEP amplitudes of more than 50%, whereas in six patients the amplitudes only slightly increased or remained unchanged. The 17 patients with the increased TcMEP amplitudes had the greatest improvement 3 and 12 months postoperatively, based on neurological examination and the visual analog scale pain ratings (p<0.001). Intraoperative monitoring may allow rapid identification of potential damage of the neural structures and avoidance through corrective action. TcMEP and continuous EMG monitoring is an effective method for monitoring neural function cord during surgical decompression of the lumbar spine and may additionally give prognostic information for the assessment of patient outcome.