Value of electroencephalogram in prediction and diagnosis of vasospasm after intracranial aneurysm rupture.

The Electroencephalogram (EEG) of 151 patients whose ruptured aneurysm was confirmed by CT scan and angiography was recorded on the first day (D1) and the fifth day (D5). On D1, EEG had a prognostic value: among 46 patients with normal EEG, 72% presented neither further electrical ischaemic features nor delayed angiographic vasospasm; on the other hand, when bilateral bursts of slow waves, "axial bursts" or slow delta waves were recorded (78 cases), 97% exhibited EEG signs of ischaemia and angiographic vasospasm a few days later. These data were clearly related to the importance of the haemorrhage, specially when thick clots in the subarachnoid cisterns were found on the CT scan. On D5, EEG had a diagnostic value: focal or asymetrical bilateral delta waves occurring at that date seemed to correspond to ischaemia; among 107 patients with these electrical features, an angiographic vasospasm appeared in 96% of cases, and the importance of electrical abnormalities could be related to the degree of arterial narrowing. We conclude that EEG data are very useful in prediction as well in recognition of post-subarachnoid haemorrhage ischaemia due to vasospasm and are sufficiently precise to postpone control angiography and operation, when delayed surgery is programmed.