[A comparative study of clinical signs, computed tomography, and electroencephalography after direct operation of ruptured anterior communicating aneurysms--Part I: Analysis of the cases with mental signs of mild degree].

Eight cases with ruptured anterior communicating aneurysms, who developed mental signs of mild degree lasting more than two weeks following direct operation, were subjected to our study. The following results were obtained. The mental signs of mild degree in 8 cases consisted of memory and emotional disturbances. The main findings of CT scan was low density area in the subcortical and cortical areas of the frontal lobe. There was no close correlation on CT findings between memory and emotional disturbances. Abnormal density areas were detected on CT scan, but EEG showed no localized abnormalities of slow waves. Abnormal density areas were not clearly shown on CT, but EEG showed localized abnormalities. Background activities on EEG were favorable despite lesions detected on CT. Either local or diffuse abnormalities were observed in EEG background activities while no abnormal mental signs were recognized. In cases with no apparent abnormal findings on CT and with favorable background activities on EEG, EEG showed marked build up during hyperventilation. As indicated by the above data, comparative studies of CT and EEG findings revealed differences in sites of abnormalities and degree of abnormalities. This is considered caused by a possible increase in cerebral blood flow and metabolism at initiation of chronic stage following subarachnoid hemorrhage-resulting in the disappearance of abnormalities on EEG.