Computer-analyzed EEG before and after bypass surgery. Quantification by a computerized wave form recognition method.

Chronological changes of the EEG before and after extracranial-intracranial arterial bypass surgery were studied on 12 patients with minor completed stroke of the carotid circulation. Instead of a power spectrum used in the conventional computer analysis, a wave form recognition method, which well correlated with visual assessment of the EEG, was applied to the present computer analysis of the EEG. The EEG changed mainly in the parietal, occipital, anterior and middle temporal records of the affected cerebral hemisphere. Deterioration of the EEG continued until 1 month, and improved gradually during 3 and 6 months after the operation. However, it was difficult to conclude that the EEG improved by surgery.