The Use of Electroencephalography and Brain Protection during Operation for Basilar Aneurysms

Abstract

Abstract Intraoperative monitoring with electroencephalography and the use of brain protection with steroids, phenytoin, mannitol, and pentobarbital or etomidate were evaluated in 15 patients undergoing operation for an aneurysm of the upper basilar artery. One patient harbored a basilar trunk aneurysm, 1 an aneurysm of the proximal posterior cerebral artery, 3 an aneurysm of the superior cerebellar artery, and 10 an aneurysm at the basilar tip. The size of the aneurysms varied between 5 and 30 mm. Subarachnoid hemorrhage was the symptom exhibited in 12, mass effect the symptom in 2, and 1 patient was asymptomatic but had an angiogram because of amaurosis. There were 9 patients with multiple aneurysms, 5 of whom had aneurysms of the bilateral anterior circulation. Four patients underwent operation early. In 2 patients, the basilar artery was the sole or main blood supply of the whole brain. All patients except the one with the basilar trunk aneurysm were operated on via a transsylvian approach. All patients received 500 to 800 mg of phenytoin and 10 to 20 mg of dexamethasone shortly before and during surgery, and mannitol (0.8 g/kg) 15 minutes before the induction of hypotension or temporary clipping. Three patients showed slowing of electrical activity over the right hemisphere as a result of retraction of the internal carotid artery; with repositioning of the retractor, this disappeared within 10 minutes. Electrocortical silence was induced in 8 patients; this was in anticipation of prolonged moderate hypotension in 2, short deep hypotension in 2, temporary clipping of major vessels—including the basilar artery—in 2, and a combination of deep hypotension combined with temporary clipping in 2. At present, etomidate is preferred over thiopental for inducing electrocortical silence because it has no cardiovascular depressant effects, even in massive doses. Three patients awoke with contralateral hemiparesis, 2 of whom had spontaneous changes in the electroencep halogram and 1 in whom electrocortical silence was present for 1 hour. In all 3 patients, the electroencephalogram had returned to normal by the end of the operation, and the hemiparesis had completely resolved within 4 hours. One patient, in whom the basilar artery itself had ruptured and had to be occluded permanently, died. One patient, whose status was Grade 4 when operation was performed on Day 25, remained severely disabled. All other patients made a good recovery. The electroencephalogram was helpful in 10 cases (67%), and it allowed the surgeon to operate without stress in an unhurried manner and, when combined with pharmaceutical brain protection—even in the presence of deep hypotension—to perform temporary clipping.