Differences in the Electrophysiological Monitoring Results of Spinal Cord Arteriovenous and Intramedullary Spinal Cord Cavernous Malformations

OBJECTIVE: Spinal arteriovenous malformations (SAVMs) and intramedullary spinal cord cavernous malformations (ISCCMs) have a very low incidence of disease. The purpose of this study was to compare the differences in electrophysiologic monitoring in these 2 surgeries. METHODS: The study included 109 patients (SAVMs, n = 55; ISCCMs, n = 54) recruited from November 2012 to January 2016. All patients underwent electrophysiologic monitoring during the entire operation, including somato-sensory-evoked potentials, motor-evoked potentials, and electromyography. We used an amplitude reduction of >80% as warning criterion for motor-evoked potentials and an amplitude reduction of more than 50% and latency prolongation of more than 10% as warning criteria for somatosensory-evoked potentials. RESULTS: In our study, the sensitivity and specificity of intraoperative monitoring during SAVM surgery were 77.3% and 87.1%, respectively. The sensitivity and specificity of intraoperative monitoring during ISCCM surgery were 68.8% and 83.3%, respectively. We found that 21 patients with SAVM showed permanent changes, 17 had immediate postoperative impairment, 8 recovered before discharge, and 5 showed neurologic deficits at long-term follow-up. Of the 17 patients with ISCCMs showing permanent changes, 11 had immediate postoperative impairment, 5 recovered before discharge, and 2 had long-term residual neurologic deficits. CONCLUSIONS: Electrophysiological monitoring provides effective guidance during operation on spinal vascular malformations. Electrophysiologic monitoring revealed that surgical resection of SAVMs resulted in more permanent changes and postoperative dysfunction when compared with ISCCMs. The incidence of both false-positive and -negative results suggests that electrophysiologic monitoring cannot fully predict the complete function of the patients.