Application of intraoperative motor evoked potential monitoring during giant internal carotid artery aneurysm surgery using prolonged temporary occlusion

Abstract

Background: Clipping and bypass surgery are common therapeutic options for the management of giant internal carotid artery (ICA) aneurysms. However, potential ischemic risks may be exaggerated by prolonged temporary occlusion (PTO) during the surgery. Monitoring motor-evoked potentials (MEPs) is a sensitive technique for detecting potential ischemia intraoperatively. This preliminary study was designed to evaluate the effectiveness of applying MEP monitoring during giant ICA aneurysm surgery using PTO.

Methods: From July 2009 to July 2012, 11 patients with giant ICA aneurysms who could not pass the preoperative hemodynamic evaluations were enrolled in this study. MEP monitoring was utilized intraoperatively in all cases. Clipping was performed if there were no significant MEP changes under PTO. A variant extracranial-to-intracranial (EC-IC) bypass was performed if there was reproducible loss of MEP signals after PTO or unclippable anatomic features.

Results: Five patients underwent clipping alone and six underwent bypass. There were no significant differences in baseline clinical data between the two groups. The overall percentage of patients with good outcomes (Glasgow Outcome Score ≥4) improved from 72.7 % (8/11) postoperatively to 90.9 % (10/11) after 26.0 ± 9.5 months of follow-up. There were no significant differences between the clipping and bypass groups regarding short- and long-term outcomes (p = 0.545 and p = 1.000).

Conclusions: MEP monitoring is useful for evaluating the safety of PTO, surgical strategy, and outcomes of giant ICA aneurysm surgery. Direct clipping during safe PTO under intraoperative MEP monitoring is applicable for giant ICA aneurysms. Its use achieved favorable outcomes by indicating the need for bypass surgery.

Keywords: Bypass; Clipping; Internal carotid artery; Intracranial aneurysm; Motor evoked potential; Surgery.