[Transcranial motor evoked potentials monitoring for cerebral aneurysm surgery]

To evaluate the usefulness of transcranial motor evoked potential(MEP)monitoring for aneurysm surgery.

Sixty-four patients undergoing aneurysm surgery were included in the study. We recorded MEP responses at craniotomy, when dissecting the aneurysm and surrounding tissue, after clipping, and during temporary clipping of the parent artery. We examined the relations between MEP wave pattern change and postoperative motor function.

In all of the patients MEPs were recordable for continuous neurophysiological monitoring of the vascular territory of interest throughout the surgery. In 16 patients, significant intraoperative MEP changes occurred. Of these patients, three patients presented with postoperative transient motor deficit. From the changes in MEP wave recording after aneurismal clipping and temporary occlusion of the parent artery. We speculated that the maximal time allowed for occlusion of the perforating arteries without ischemic damage is five minutes. Intraoperative MEP changes had a sensitivity of 100%(3/3)and specificity of 78.7%(48/61). The positive predictive value of postoperative motor deficit was 18.8%(3/16), and the negative predictive value was 100%(48/48). It was important to carry out MEP monitoring, so as not to produce false-negatives.

Intraoperative transcranial MEP monitoring is useful for predicting motor function after aneurysm surgery.