Microsurgical treatment outcomes of brainstem cavernous malformation: Subgroup comparison depending on application of intraoperative neurophysiologic monitoring

Objectives: Controversies regarding effectiveness of intraoperative neurophysiologic monitoring (IONM) in resection of brainstem cavernous malformations (CMs) have been argued. Immediate postoperative surgical outcomes, long term functional outcomes including cranial nerve deficits prognosis and modified Rankin Scale (mRS) were investigated. Methods: Total 47 patients of brainstem CMs who underwent surgery from January 2000 to November 2016 were identified and analyzed. All patients' clinical, radiological and surgical records were obtained and reviewed. Results: The incidence of aggravation of immediate postoperative pre-existing neurological deficits in surgery without IONM and with IONM group were 41.7% and 20%, respectively (p = 0.04). The incidence of newly developing postoperative neurological deficits in surgery without IONM and with IONM were 50% and 20%, respectively (p = 0.06). The postoperative surgical complications such as intracerebral hemorrhage/intraventricular hemorrhage, subdural hemorrhage, cerebrospinal fluid leakage, hydrocephalus were occurred 16.6% vs 8.7% in surgery without IONM and with IONM group, respectively (p = 0.06). The functional outcomes of each cranial nerve were not statistically significant. There was no statistically significant factor affecting immediate postoperative neurological deterioration in univariate analysis. The mRS after 1-year in surgery with IONM group showed statistically significant improvement compared to preoperative and 1-month postoperative period (from 3.4 to 1.87, p < 0.01). Conclusions: The application of IONM during brainstem CM surgery might prevent postoperative deterioration of pre-existing neurological deficits and the development of additional deficits. Further, it might be associated with better functional outcomes. Keywords: Brainstem cavernous malformation, Intraoperative monitorin