Effectiveness and Limitations of Intraoperative Monitoring with Combined Motor and Somatosensory Evoked Potentials During Surgical Clipping of Unruptured Intracranial Aneurysms

Abstract

OBJECTIVE: Postoperative neurologic deficits are one of the devastating complications that can result from surgical clipping of unruptured intracranial aneurysms. Intraoperative monitoring (IOM) of motor and somatosensory evoked potentials (EPs) has been used to reduce neurologic sequelae. We evaluated the effectiveness and limitations of IOM in prevention of surgical complications during aneurysm clipping. METHODS: A retrospective analysis was performed, involving 386 operations for 429 unruptured intracranial aneurysms in 386 patients with consecutively collected IOM data. RESULTS: Significant EP changes were detected during clipping of 23 aneurysms in 23 patients (5.4% of aneurysms). Among them, 8 patients (accounting for 2.1% of operations and 1.9% of aneurysms) experienced postoperative motor deficits, including 3 permanent and 5 temporary motor deficits with corresponding radiologic lesions. In detecting postoperative motor deficits, the sensitivity and specificity of motor EP monitoring were 0.38 and 0.99, respectively, and those of somatosensory EP monitoring were 0.25 and 0.96, respectively. Seven patients (1.8% of operations) with unchanged EPs had other kinds of postoperative neurologic complications, including altered mentality in 5 cases, motor aphasia in 1, and gaze limitation in 1, with corresponding radiologic abnormalities. However, all 7 patients with other neurologic symptoms recovered within 6 months after surgery. CONCLUSIONS: IOM of motor and somatosensory EPs was useful and reliable in predicting and preventing postoperative motor deficits. However, it also showed some limitations in the significance of positive EP changes and detection of neurologic deficits other than motor function.