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Intraoperative neurophysiological monitoring (IONM) represents one of the available technologies able to assess ischemia and aimed to improve surgical outcome reducing the treatment related morbidity in surgery for intracranial aneurysms. Many studies analyzing the impact of IONM are poised by the heterogeneity bias affecting the cohorts. We report our experience with IONM for surgery of unruptured middle cerebral artery (MCA) aneurysm in order to highlight its influence on functional and radiological outcome and surgical strategy. We retrospectively reviewed all MCA unruptured aneurysms treated between January 2013 and June 2021 by our institutional neurovascular team. Patients were divided into 2 groups according to the use of IONM. A total of 153 patients were included in the study, 52 operated on without IONM and 101 with IONM. The groups did not differ preoperatively regarding clinical status and aneurysm characteristics. Patients operated with IONM had better functional outcomes at discharge as well as at follow-up (p= 0.048, p=0.041) due to lower symptomatic ischemia and better radiological outcome due to lower rate of unexpected aneurysmal remnants (p= 0.0173). The introduction of IONM changed the use of temporary clipping (TeC), increasing its average duration (p= 0.01) improving the safety of dissecting and clipping the aneurysm. IONM in surgery for unruptured MCA aneurysm could improve the efficacy and safety of clipping strategy in the way it showed a role in changing the use of TeC and was associated to the reduction of unexpected aneurysmal remnants’ rate and improvement in both short- and long-term patient’s outcome.

Objective: To study clinical significance of augmentation of intraoperative motor evoked potentials (MEPs) during direct open surgery for middle cerebral artery (MCA) aneurysms. Methods: Between 2009 and 2017, 134 MCA aneurysm surgeries were performed with intraoperative MEP monitoring. The frequency and cause of augmentation with >50% increase of MEP amplitude from baseline were studied. Factors associated with MEP augmentation were investigated. Results: MEP augmentation was demonstrated in 9 patients. All 9 events were observed just after application of the temporary clip to the parent artery. The ratio of the maximum amplitude to baseline was 2.6 ± 1.1 at an mean of 2.4 ± 1.1 minutes after parent artery occlusion. Ten patients who did not show MEP augmentation after parent artery occlusion were compared with the patients showing MEP augmentation. The distance of the temporary clip point from the midline was smaller in patients with MEP augmentation compared with patients without MEP augmentation (P = 0.033). Conclusions: MEP augmentation was thought to be an early ischemic sign preceding a significant decrease in MEPs during MCA aneurysm surgery. Transient augmentation of MEPs was more frequently observed in cases with a temporary clip applied to the more proximal part of the MCA., 博士（医学）・乙第1445号・令和元年12月5日, © 2019 Elsevier Inc. All rights reserved.

Objective: To study clinical significance of augmentation of intraoperative motor evoked potentials (MEPs) during direct open surgery for middle cerebral artery (MCA) aneurysms. Methods: Between 2009 and 2017, 134 MCA aneurysm surgeries were performed with intraoperative MEP monitoring. The frequency and cause of augmentation with >50% increase of MEP amplitude from baseline were studied. Factors associated with MEP augmentation were investigated. Results: MEP augmentation was demonstrated in 9 patients. All 9 events were observed just after application of the temporary clip to the parent artery. The ratio of the maximum amplitude to baseline was 2.6 ± 1.1 at an mean of 2.4 ± 1.1 minutes after parent artery occlusion. Ten patients who did not show MEP augmentation after parent artery occlusion were compared with the patients showing MEP augmentation. The distance of the temporary clip point from the midline was smaller in patients with MEP augmentation compared with patients without MEP augmentation (P = 0.033). Conclusions: MEP augmentation was thought to be an early ischemic sign preceding a significant decrease in MEPs during MCA aneurysm surgery. Transient augmentation of MEPs was more frequently observed in cases with a temporary clip applied to the more proximal part of the MCA., 博士（医学）・乙第1445号・令和元年12月5日, © 2019 Elsevier Inc. All rights reserved.