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Introduction: Postoperative delirium (POD) that is associated with intracranial surgeries can have several adverse outcomes, including a high rate of morbidity and mortality. The use of intraoperative neurophysiological monitoring (IONM) via somatosensory evoked potentials (SSEPs) and electroencephalography (EEG) provides continuous information regarding cerebral blood flow (CBF) during aneurysm clipping. In this study, we hypothesize that CBF changes during aneurysm clipping increase the risk of POD. We aimed to demonstrate that significant changes in IONM data during surgery increase the risk of POD after adjusting for clinical and intraoperative factors., Methods: 470 patients undergoing craniotomy for aneurysm clipping surgery with IONM were retrospectively reviewed for the development of POD. Significant IONM changes were evaluated based on a visual review of EEG and SSEP data and documentation of significant changes during surgery. Data changes during IONM were classified as SSEP changes, EEG changes, or IONM changes (SSEP and/or EEG changes)., Results: Of the 470 patients who underwent aneurysm clipping, 115 (24.5%) had POD and 35 (30.4%) had IONM changes. IONM and SSEP changes were significantly associated with POD (P< 0.001). After adjusting for confounding variables, IONM and SSEP changes were significantly associated with POD (OR 2.4 (CI 1.40-4.17); P=0.002, OR 2.49 (CI 1.39-4.45); P = 0.002, respectively). We also found that the odds of POD were higher in patients with ruptured aneurysms, and in patients who developed focal neurological deficits post-operatively (OR 2.76,1.72-4.42; P< 0.001, OR 2.11,1.02-4.36, P=0.04, respectively)., Conclusion: Patients who develop POD after craniotomy for aneurysm clipping surgery are twice as likely to have experienced significant IONM or SSEP changes during the surgery. Patients with ruptured aneurysms and who develop post-operative focal neurological deficits are also more than twice as likely to develop POD. These findings provide a strong platform for future research in testing therapeutic interventions based on IONM changes, which aim to decrease the risk of POD after aneurysm clipping surgeries., (S. Karger AG, Basel.)

Objective: Recovery of abducens nerve palsy (ANP) after endoscopic endonasal skull base surgery (ESBS) has been shown to be potentially predicted by postoperative ophthalmological examination. Triggered electromyography (t-EMG) and free-run electromyography (f-EMG) activity provide an intraoperative assessment of abducens nerve function, but associations with long-term ANP outcomes have not been explored. The objective of this study was to describe intraoperative abducens EMG characteristics and determine whether these electrophysiological profiles are associated with immediately postoperative and long-term ANP outcomes after ESBS., Methods: The authors conducted a 5-year (2011-2016) retrospective case-control study of patients who underwent ESBS in whom the abducens nerve was stimulated (t-EMG). Electrophysiological metrics were compared between patients with a new postoperative ANP (cases) and those without ANP (controls). Pathologies included chordoma, pituitary adenoma, meningioma, cholesterol granuloma, and chondrosarcoma. Electrophysiological data included the presence of abnormal f-EMG activity, t-EMG stimulation voltage, stimulation threshold, evoked compound muscle action potential (CMAP) amplitude, onset latency, peak latency, and CMAP duration at various stages of the dissection. Controls were selected such that pathologies were similarly distributed between cases and controls., Results: Fifty-six patients were included, 26 with new postoperative ANP and 30 controls without ANP. Abnormal f-EMG activity (28.0% vs 3.3%, p = 0.02) and lack of response to stimulation (27% vs 0%, p = 0.006) were more frequent in patients with immediately postoperative ANP than in controls. Patients with immediately postoperative ANP also had a lower median CMAP amplitude (35.0 vs 71.2 μV, p = 0.02) and longer onset latency (5.2 vs 2.8 msec, p = 0.04). Comparing patients with transient versus persistent ANP on follow-up, those with persistent ANP tended to have a lower CMAP amplitude (12.8 vs 57 μV, p = 0.07) and higher likelihood of not responding to stimulation at the end of the case (45.5% vs 7.1%, p = 0.06). Abnormal f-EMG was not associated with long-term ANP outcomes., Conclusions: The presence of f-EMG activity, lack of CMAP response to stimulation, decreased CMAP amplitude, and increased CMAP onset latency were associated with immediately postoperative ANP. Long-term ANP outcomes may be associated with t-EMG parameters, including whether the nerve is able to be stimulated once identified and CMAP amplitude. Future prospective studies may be designed to standardize abducens nerve electrophysiological monitoring protocols to further refine operative and prognostic utility.