Facial corticobulbar motor-evoked potential monitoring during the clipping of large and giant aneurysms of the anterior circulation

Surgical outcomes for large and giant intracranial aneurysms are suboptimal. Two important reasons for higher complication rates are either occlusion of perforators or parent arteries during aneurysm clipping, or prolonged temporary occlusion of the main arteries. Somatosensory-evoked potential (SSEP) monitoring and transcranial motor-evoked potential (TcMEP) monitoring are standard techniques for monitoring ischemia either during temporary arterial occlusion or after permanent clipping. In our study, facial corticobulbar motor-evoked potential (FCoMEP) monitoring was included to determine whether this modality improved intraoperative monitoring. FCoMEP were recorded intraoperatively in 21 patients undergoing surgical clipping of large and giant aneurysms of the anterior circulation. Valid TcMEP parameters were obtained for all patients. A correlation tending to significance between a prolonged temporary clipping time and TcMEP decrement was observed. In addition to this, the inclusion of FCoMEP improved the sensitivity of extremity muscle motor-evoked potential (ExMEP, which included TcMEP) monitoring (from 80% to 100%). In the long-term assessment, a favorable outcome was achieved in 16 of the 21 patients (76%). In conclusion, FCoMEP provides complementary corticobulbar tract information for detecting perforating vessel compromise that may lead to motor impairment and that is not identified by ExMEP.