Abstract
The retrogradely investigated results of 80 surgical treatments of unruptured cerebral aneurysms. The aneurysms were located at the internal carotid artery (35 aneurysms), the middle cerebral artery (32), the anterior communicating artery (9) and the vertebrobasilar artery (6). There were 17 large or giant aneurysms involving 3 middle cerebral arteries and 4 vertebrobasilar arteries. Somatosensory evoked potential (SEP) was intraoperatively recorded in 42 patients. Amplitude of N20/P25 was especially observed. The operative field was observed using an optic fiberscope in some patients. Blood flow in aneurysm or parent artery was examined by Doppler microvascular sonography.
Seven of 38 patients without SEP monitoring had postoperative neurologic deteriorations, including 3 patients with permanent neurologic deficits. On the other hand, 5 of 42 patients with SEP monitoring had reversible postoperative neurologic signs but no permanent deficits. Changes in SEP of these 5 patients were significant decrease in the amplitude of N20/P25 or disappearance of the N20. However, these changes in SEP were recovered at the end of the operations. Patients who demonstrated no significant decrease in the amplitude of N20/P25 had no neurologic deterioration.
Causes of significant decrease in the amplitude of N20/P25 included retraction of the brain (5 patients), temporary clipping (2), retraction of the internal carotid artery (2), occlusion of the middle cerebral artery (1), and occlusion of the perforating artery of the posterior cerebral artery (1). Seven of 16 patients with large or giant aneurysm demonstrated significant decrease in the amplitude of N20/P25. Doppler flowmetry was useful for detecting incomplete occlusion of aneurysm and patency of the parent artery. The optic fiberscope was also useful for confirming no sacrifice of the vessels near the aneurysm.
We conclude that SEP monitoring is a reliable method for safe operation of unruptured aneurysms, especially large or giant aneurysms, and in the patients with ischemic vascular disease. In addition microvascular sonography Doppler and optic fiberscope are helpful in decreasing operative complications.
