Current Concepts of Cerebrovascular Disease — Stroke Non-invasive Carotid Evaluation

STROKE DUE TO ATHEROMATOUS DISEASE of the carotid artery is preventable by endarterectomy if a causative lesion is identified early enough. Despite its limitations arteriography remains the definitive test for carotid disease. Ideally, arteriography should be done when the risk of stroke is considerably greater than the risk of a complication from the diagnostic procedure. The warning signs of a carotid stroke, however, are often not specific; a bifurcation bruit and/or history suggestive of transient ischemic attacks (TIA) are not always sufficient to justify undertaking arteriography. Additional pathoanatomical and pathophysiological data are required to "rule in" an arteriogram in these situations. Non-invasive laboratory methods of carotid evaluation extend the sensitivity and perceptiveness of the eyes, ears, and fingers and facilitate a neurovascular examination that is more specific for a diagnosis of carotid disease. Because the non-invasive tests permit sequential evaluations, they can also provide important information on the natural history of carotid lesions. To be effective non-invasive carotid evaluation requires a selected battery of tests.' Carotid disease produces anatomical change at the common carotid bifurcation as well as pathophysiological changes both at the bifurcation and in distal circulatory beds. We classify the non-invasive tests as "direct" if they monitor the bifurcation itself and "indirect" if they monitor distal circulatory beds for evidence of carotid disease (table). The direct tests are further divided into those that assess the anatomical status and those that are physiological monitors. The indirect tests are grouped according to whether they monitor the cerebral or orbital circulations, and the tests of the orbital circulation are subclassified into those which monitor the superficial or the deep orbital circulatory beds (table). Stroke in patients with carotid lesions may be due to thromboemboli arising from ulcerated atheromatous carotid plaques or from impaired distal flow.