The silent brain infarct in carotid surgery

Abstract

The destructive potential of carotid artery disease is underestimated by the clinical classification that surveys only that part of the brain with clear somatic representation. Asymptomatic patients are found to have brain infarctions on CT scan for which there is no history or symptom. To assume “benign” behavior of a carotid lesion, a patient must be both asymptomatic and “asignomatic.” Likewise, when the morbidity of carotid operations is reported, silent infarcts must somehow be taken into account. We investigated this “silent” disease in a prospective study of 100 carotid operations done on 91 patients over a 9-month period in our service. All patients had arch and four-vessel selective arteriography. Detailed neurologic examinations and CT scans were done before and after surgery. Of the 91 patients, 78 (86%) had a history of neurologic problems. Preoperative CT scans showed infarction in 21 patients, but only 57% of the infarctions correlated with symptoms and/or history. Among patients with a history of transient ischemic attack (TIA), 19% had an infarction seen on CT scan; however, among those patients who had lateralizing TIAs, the incidence of unsuspected infarction was higher (26%). Arteriography showed a lesion in all carotid systems supplying a symptomatic or infarcted hemisphere. Following 100 operations, four patients had neurologic abnormalities—two had transient hemianopsia and two had hemiparesis. CT scan showed a new infarct in all four patients as well as in eight other patients without neurologic findings; two of these silent postoperative infarctions were found in the hemisphere opposite the side of the operated carotid artery. The clinical morbidity of this prospective series consisted of two TIAs (2%) and two strokes (2%). With CT evidence used as a criterion for infarction, the morbidity rate was 12%. CT scanning added to clinical studies of carotid disease and its surgical management shows that the morbidity of both is much greater than that inferred by traditional clinical assessment.