Intramedullary spinal cord tumors: the value of intraoperative neurophysiological monitoring in a series of 57 cases from two Italian centers

BACKGROUND: Intramedullary spinal cord tumors are rare lesions of the central nervous system. Anatomical, molecular and radiological features are well defined, but correct management is still matter of debate. Pertinent literature has reported conflicting opinions regarding the use of intraoperative electrophysiological monitoring (IONM) in the surgical treatment of this kind of lesions, recently. We report a retrospective study from two Italian centers, in order to highlight the usefulness of IONM in the management of intramedullary lesions. METHODS: We performed a retrospective review of patients with intramedullary spinal tumor who underwent surgical resection from February 2011 to February 2018 in two different institutions. Clinical and radiological data, lesion features, timing of symptom onset and IONM findings were recorded. The IONM included somatosensory-evoked potentials (SSEP), motor-evoked potentials (MEP) and D-Wave whenever possible. We evaluated the outcome according to the Modified McCormick scale. We also evaluated the accuracy and relevance of surgical outcomes for each evoked potential (SSEP, MEP, D-Wave). RESULTS: A total of 57 patients were included. A gross total removal was achieved in 46 cases. Neurological follow-up was assessment at 3 days, and 3 and 6 months after surgery. Comparing the preoperative status and 6 months follow-up: the modified McCormick scale showed a neurological stability for 30 patients (52.63%), a worsening of neurological status for 7 patients (12.28%) and an improvement for 20 patients (35.08%). IONM presented high accuracy (sensibility of 100% and specificity of 95.65%) and significantly predicted postoperative permanent motor deficits (P<0.0001; AUC=0.978). D-Wave appeared to have significant greater predictive value than MEP and especially SSEP alone (0.967 vs 0.722 vs 0.542; P=0.044 and P<0.001 respectively). CONCLUSIONS: The gold standard in the intramedullary lesion treatment is maximal safe resection with good neurological outcome, as shown in our patients. The use of IONM is helpful in intramedullary tumors resection in order to minimize postoperative neurological deficits and our analysis suggests that the use of D-Wave presents a statistically significant higher accuracy for predicting postoperative deficits than SSEP and MEP alone.