Factors Affecting Intraoperative Electroencephalographic Changes during Carotid Endarterectomy

ABSTRACT

BACKGROUND: Continuous electroencephalographic (EEG) monitoring is a widely used method of operative surveillance during a carotid endarterectomy. It is widely accepted that intraoperative EEG changes are closely related with increased risk of postoperative stroke. If there are factors affecting EEG changes on preoperative evaluations, they may be helpful in predicting postoperative neurologic deficits, selecting patients, and, furthermore, reducing morbidity. METHODS: We reviewed the cases of 47 patients who received a CEA from January 1995 to August 1997. There were 10 cases of intraoperative EEG changes. Dividing the 47 cases into two groups (10 cases of positive EEG changes vs. 37 cases of negative EEG changes), we compared several factors between the two groups, such as patient's characteristics (age, history of smoking, and presence of hypertension, diabetes, or heart disease), operative indication (asymptomatic, TIA, stroke), carotid lesions (site, extent of stenosis, presence of ulceration, stenosis of the contralateral carotid artery), and carotid angiographic findings. RESULTS: In the aspect of patient's characteristics, operative indications, and carotid lesions, there were no statistically significant differences between the two groups. In the carotid angiogram, the contralateral carotid angiogram is the only one statistically useful (p<0.001) in predicting intraoperative EEG changes, with a negative predicting value of 100%. The existence of collaterals in the vertebral angiograms showed differences in frequency between the two groups, but this was statistically not significant. CONCLUSION: The preoperative carotid angiogram might be considered as a useful evaluation for predicting intraoperative EEG changes. If more data are accumulated, the other factors should reviewed again. Recently, positron emission tomography (PET) and transcranial doppler (TCD) have been performedin some patients. We think that these studies, in conjunction with the carotid angiogram, will be more helpful as more data are accumulated.