Motor evoked potentials (MEPs) with somatosensory evoked potentials (SSEPs) have been used to prevent neurological
complication during cerebral aneurysm surgery. This case shows postoperative anterior choroidal artery (AChA)
infarction with decreased SSEPs, in spite of preserved MEPs during aneurysm clipping. A 58-year-old man with
ruptured aneurysm between right internal carotid artery and AChA received aneurysm clipping. During temporal arterial
clipping, left tibial SSEPs amplitude decreased by 95% and median SSEPs decreased by 89% of the baseline. SSEPs
changes lasted for 10 minutes and there was no change of MEPs. After operation, mental state changed to drowsy and
left side weakness occurred. Cerebral angiography showed non-visualized right AChA and brain MRI showed right AChA
infarction. MEPs are difficult to be performed continuously because patient movement may interfere with microsurgery
and raise safety concerns. We suppose that SSEPs are possibly complement of MEPs to take consider the subcortical
perfusion such as AChA.