Value of electroencephalography (EEG) before and after surgery of intracranial aneurysms.

Electroencephalographic (EEG) investigations were done in 36 patients with intracranial aneurysms, before and after surgery. Thirty five of them suffered from subarachnoid hemorrhage (SAH). Pre-operatively, there was no correlation between patients' age or sex and localisation of the aneurysm or degree of EEG disturbances. The most frequent finding was a generalised slowing, the degree of which depended on the time from bleeding to EEG. Focal abnormalities were due to spasms of the vessels or intracerebral haematomas. There was a high correlation with neurological deficits. Post-operatively, EEG disturbances became worse in 21 cases. Generalised and focal abnormalities increased. These were due to focal oedema and the operative approach. The EEG could be correlated very well with the findings from other investigative methods (CT scanning, angiography). The EEG, as a functional method, showed very well the whole state of the brain after bleeding and after operation.