Cerebral Embolism as a Cause of Stroke and Transient Ischemic Attack.

The most frequent cause of stroke and transient ischemic attacks is cerebral embolism. Cardiogenic cerebral embolization is common among patients with any cause of atrial fibrillation (AF) but particularly in AF resulting from rheumatic and arteriosclerotic heart disease. Rare causes of cerebral embolism include fat entering the bloodstream after trauma, tumor cells arising from atrial myxomata, and gas embolism. Cerebral embolic infarctions and their sources of origin can now be confirmed during life by many invasive (I) and noninvasive (NI) procedures including computerized tomography (CT) scanning (NI), magnetic resonance imaging (MR) (NI), contrast angiography (I), digital subtraction angiography (I), magnetic resonance angiography (NI), carotid Doppler and transcranial Doppler (NI), and echocardiography (NI) without and with contrast. These tests visualize the following: embolic occlusions of small and large cerebral arteries, resultant cerebral infarctions in appropriate vascular territories, plaques within the aorta, subclavian, vertebral, and carotid arteries, and mural thrombi located within the heart and aortocephalic arteries. Transcranial Doppler monitoring of the middle cerebral artery detects both small (asymptomatic) and large (symptomatic) cerebral emboli, as well as transseptal cardiac shunting, which is a cause of paradoxical embolization. Holter monitoring detects episodic cardiac dysrhythmias not apparent during routine ECG. CT or MRI identify cerebral infarctions resulting from virtually all large cerebral emboli. Early recognition and identification of types of cerebral embolism are important because of the availability of effective prophylactic therapies. (ECHOCARDIOGRAPHY, Volume 13, September 1996)