THE ELECTROENCEPHALOGRAM IN ACUTE VASCULAR LESIONS OF THE BRAIN STEM AND THE CEREBELLUM

Abstract

The correlation between EEG (electro-encephalograph) and autopsy findings was studied in 20 cases of acute vascular lesions of the brain stem or the cerebellum. In 2 patients with lesions rostral to the pons EEG showed diffuse 1-3 c/sec activity. In the remaining patients, all of whom had pontine or cerebellar lesions, the record was either normal or presented uncharacteristic slow wave abnormalities, in some instances combined with focal sharp waves. In all cases of lower brain stem lesion with abnormal EEG the autopsy revealed either manifest supratentorial softenings or a pronounced cerebral arteriosclerosis. In eleven of the 20 patients the occipital alpha amplitude was lower than or equal to the parietal, probably indicating a vascular insufficiency in the territory of the posterior cerebral arteries. The EEG findings associated with different states of consciousness are discussed. In particular it is noted that two patients with extensive pontine infarctions presented a normal EEG during the state of coma. In accordance with the experimental evidence our results indicate that upper brain stem lesions will provoke diffuse slow wave abnormalities in the EEG, probably owing to damage to the cephalic portion of the reticular activating system. On the other hand, even extensive pontine or cerebellar lesions do not appreciably influence the EEG. Most of the EEG abnormalities observed in patients with lower brain stem lesions are undoubtedly due to circulatory disturbances affecting more rostral parts of the brain.