Application of intraoperative monitoring with cortical electrodes in intracranial aneurysm surgery

Abstract

Objective To study the value and significance of cortical electroencephalogram (EEG)and direct cortical motor evoked potentials (MEP) monitoring in intracranial aneurysm surgery.Methods Scalp EEG,SEP,MEP and cortical EEG,MEP were monitored during surgical management of intracranial aneurysms by pterional craniotomy in forty-two patients.Monitoring results ,clinical outcomes and their correlation were prospectively analyzed.Results Cortical MEP could be elicited in thirty-six patients intraoperatively.Cortical MEP could not be induced in five patients with anterior cerebral artery system aneurysms and one patient with non-anterior cerebral artery system aneurysm.Changes of intraoperative monitoring results occurred in eight patients,including SEP in four cases,cortical EEG in six cases,scalp EEG in two cases,cortical MEP in seven cases and scalp MEP in five cases.Among the six patients with non-anterior cerebral artery system aneurysms and showing changed cortical MEP,only three of them presented changes in scalp MEP.Scalp EEG had significant change during surgery in two patients,who suffered severe intraoperative ischemia.For those patients whose evoked potentials could be elicited before the end of operation,their neurological function recovered well after operation.Conclusions Cortical MEP need small volume of stimulus and it is more suitable to be applied in intraoperative monitoring during surgery for middle cerebral artery,internal carotid artery and posterior communicating artery aneurysrns.Its sensitivity is higher than that of scalp MEP.The sensitivity of cortical EEG monitoring is superior to that of scalp EEG. Key words: Intracranial aneurysm; Cortical EEG; Cortical MEP; Intraoperative monitoring