2021 Volume 49 Issue 2 Pages 119-122
Here, we report two cases of unruptured right middle cerebral aneurysms in which intraoperative electrophysiological monitoring showed false-positive responses due to dural closure. Patient 1 was a 71-year-old woman in whom direct surgery was performed under electrophysiological monitoring using transcranial electrical stimulation (TES). Motor-evoked potentials (MEPs) were recorded from the bilateral upper extremities. The MEP amplitude decreased on the left side when the dura mater was closed. In contrast, the MEP obtained from the contralateral side showed no obvious decrease. Postoperative computed tomography images showed no ischemic lesions, and the patient was discharged without complications. Patient 2 was a 69-year-old woman in whom direct surgery was performed under electrophysiological monitoring. MEP was recorded from the left extremity. Although the MEPs were stable until dural closure, their amplitudes disappeared once the dura mater was completely closed. Postoperative radiological imaging showed no ischemic changes, and the patient was discharged without complications. MEPs may fluctuate during direct surgery due to many factors. Accordingly, the TES results can sometimes be confusing. We should be aware that a false-positive response may occur because of dural closure.
