EEG changes during carotid endarterectomy: drug effect and embolism.

Clinical neurological status and the electroencephalogram (EEG) were monitored during right carotid endarterectomy under regional anaesthesia in a patient who had suffered two prior cerebral infarctions. No change in EEG or clinical status was seen with occlusion of the carotid artery, but generalized encephalopathic changes were seen after a small dose of narcotic given before carotid occlusion. Bihemispheric changes in EEG and neurological status occurred upon release of carotid occlusion. This case demonstrates three important points. First, EEG changes can be seen with sedative or anaesthetic agents in patients who have previously suffered brain injury. Second, temporary neural dysfunction may be seen remote from the site of a localized injury to the brain--a phenomenon known as diaschisis. Finally, this report reiterates the observation that the risk of injury to the brain during carotid endarterectomy is not limited to the period of possible ischaemia during occlusion of the carotid artery.