title: Evaluation of combined use of transcranial and direct cortical motor evoked potential monitoring during unruptured aneurysm surgery.
abstract: The feasibility and reliability of combined use of transcranial and direct cortical motor evoked potential (MEP) monitoring during unruptured aneurysm surgery were evaluated. Forty-eight patients with unruptured cerebral aneurysms underwent craniotomy and neck clipping accompanied by muscle MEP monitoring. MEPs were elicited successfully by transcranial electrical stimulation in all patients. Direct cortical stimulation elicited MEPs in 44 patients. Reduction in MEP amplitude to less than 50% of baseline was considered significant. No postoperative motor paresis occurred in 39 patients in whom transcranial and direct MEPs remained unchanged. Four patients in whom direct MEPs could not be recorded had no intraoperative abnormality in transcranial MEPs and no postoperative motor dysfunction. Four of the other 5 patients manifested significant transient direct MEP changes without transcranial MEP changes. The transient MEP changes were observed in 3 patients during temporary clipping of the parent artery and in one patient with inadequate clipping of an middle cerebral artery aneurysm, and were considered due to insufficiency of blood flow. Decrease or disappearance of direct MEP waves recovered immediately after re-application of the clip and release of the temporary clip. Direct MEP waves disappeared and did not recover until the end of microsurgical procedures in one patient, although transcranial MEP amplitude remained at less than 50% of baseline. She developed hemiparesis postoperatively, which recovered within 6 hours. The duration of temporary occlusion in patients with direct MEP changes was significantly longer than that in patients without (p < 0.05). Direct MEP was sensitive in detecting ischemic stress to descending motor pathways during aneurysm surgery. Transcranial MEPs could be elicited in patients in whom direct MEPs could not be obtained, and during periods such as craniotomy or after dural closure, in which direct MEPs could not be recorded. These findings suggest that combined transcranial and direct cortical MEP recording may improve the feasibility and reliability of MEP monitoring during unruptured aneurysm surgery.
authors.affiliation: Department of Neurosurgery, Nara Medical University, Kashihara, Nara, Japan. myasushi@naramed-u.ac.jp
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Motoyama
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kawaguchi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Yamada
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nakagawa
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nishimura
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Hironaka
authors.forename: Young-Su
authors.initials: YS
authors.lastname: Park
authors.forename: Hironobu
authors.initials: H
authors.lastname: Hayashi
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Abe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakase
mesh_terms: D000328:Adult; D000368:Aged; D002545:Brain Ischemia / Q000175:diagnosis / Q000503:physiopathology; D003399:Craniotomy; D004525:Efferent Pathways / Q000503:physiopathology; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006225:Hand / Q000294:innervation; D006801:Humans; D002532:Intracranial Aneurysm / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010291:Paresis / Q000175:diagnosis / Q000503:physiopathology; D011183:Postoperative Complications / Q000175:diagnosis / Q000503:physiopathology; D011237:Predictive Value of Tests; D012815:Signal Processing, Computer-Assisted; D013525:Surgical Instruments