The use of electroencephalography and brain protection during operation for basilar aneurysms.

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.(ABSTRACT TRUNCATED AT 250 WORDS)