脳動脈瘤クリッピング術における術中視覚誘発電位モニタリングの有用性  [in Japanese] Intraoperative Monitoring of Visual Evoked Potential for Aneurysm Clipping Surgery  [in Japanese]

We intraoperatively monitored visual evoked potential (VEP) in 6 aneurysm clipping surgeries for 2 IC paraclinoid, 2 IC-posterior communicating artery (IC-PCoA) and 2 posterior cerebral artery (PCA) aneurysms, which had potential risk of optic pathway damage. Stable waveform was acquired throughout the procedures in all cases under total intravenous anesthesia with propofol. Reproducible transient VEP waveform decrease was observed during temporary artery occlusion, which recovered after release of temporary artery occlusion in 3 patients. No visual disturbance was encountered in this group postoperatively. On the contrary, VEP waveform decreased permanently during aneurysm dissection from the optic nerve in an IC paraclinoid aneurysm patient. The patient had severe visual dysfunction postoperatively. Our series revealed that transient ischemic dysfunction of the optic pathway caused from artery occlusion was detectable within a reversible time window; however, it seems difficult to detect mechanical damage of the optic nerve damage in a reversible time window. Intraoperative monitoring of VEP predicts postoperative visual function; reversible change in VEP means visual function is preserved, especially when the change is caused by ischemia that occurs when the artery that supplies the optic apparatus is temporarily occluded.