Differences in Multimodality Intraoperative Neurophysiological Monitoring Changes Between Spinal Intramedullary Ependymoma and Hemangioblastoma

INTRODUCTION: Intraoperative neurophysiological monitoring using transcranial muscle motor evoked potentials (MEPs) and somatosensory evoked potentials is an established method for intramedullary spinal cord tumor surgery. Ependymomas and hemangioblastomas arise in different anatomic locations and require different surgical techniques. The aim of our study was to assess differences in intraoperative neurophysiological monitoring findings between ependymoma and hemangioblastoma. METHODS: Fifty-six limbs from 16 patients diagnosed with ependymoma and 18 limbs from six patients with hemangioblastoma were included. The alarm criterion for MEPs was a 50% decrease in amplitude, whereas for somatosensory evoked potentials, it was a 50% decrease in amplitude and/or a 10% delay in latency. RESULTS: We found that 14 of the 56 ependymoma limbs (25.9%) and 8 of the 18 hemangioblastoma limbs (44.4%) showed MEP decrement during surgery. Eight limbs of patients with ependymoma (57.1%) and one limb of a patient with hemangioblastoma (12.5%) did not show recovery of MEPs at the end of surgery. Among those who showed recovery of MEPs, six ependymoma (10.7%) and six hemangioblastoma (33.3%) limbs did not show postoperative motor deficits (P = 0.04). Finally, 11 limbs of patients with ependymoma and one limb of a patient with hemangioblastoma showed postoperative weakness. CONCLUSIONS: In our study, the incidence of transient changes in MEPs was higher in hemangioblastoma than in ependymoma. Our data suggest that it may be necessary to consider tumor features and the type of surgical technique used, particularly when interpreting intraoperative neurophysiologic monitoring profiles of intramedullary spinal cord tumors such as ependymomas and hemangioblastomas.