Transient ischemic attacks: diagnosis, and medical and surgical management

Patients experiencing transient ischemic attacks (TIAs) may have a 2-year stroke rate as high as 57%, and carotid endarterectomy has been shown in prospective randomized studies to be highly effective in reducing this rate. Therefore, it is crucial to correctly identify patients with TIAs, treat underlying causes appropriately, and identify those most likely to benefit from endarterectomy. Whether in the anterior or posterior circulation, TIAs are focal neurologic events that usually last 5 to 30 minutes and are characterized by an abrupt onset followed by gradual resolution. They may be caused by artery-to-artery thromboembolism, cardiogenic embolism, or thrombosis of a small penetrating cerebral vessel (threatened lacunar infarction). A number of contributing disorders must be considered, including migraine, arterial dissection, vasculitis, thrombotic diatheses, blood dyscrasias, infections, and drug abuse. Carotid endarterectomy should be considered only for patients with hemispheric TIAs in whom lacunar events, cardiogenic embolism, and other underlying causes of stroke have been excluded and ipsilateral carotid stenosis of greater than 70% has been demonstrated. The value of endarterectomy increases: if the patient is relatively willing to take immediate risks in order to avoid future morbid events (low risk aversion) and believes stroke is a serious event, nearly tantamount to death; if the morbidity and mortality of the operation, as determined by institutional audits, is low; and if the degree of carotid stenosis is high. The value of endarterectomy declines rapidly with time elapsed from the TIA. Endarterectomy is of marginal value in patients with amaurosis fugax, of uncertain value in patients with stroke, and unlikely to be of any value in patients with asymptomatic carotid stenosis. Long-term anticoagulation has been shown to be beneficial only in patients at risk for cardiogenic embolism. Others, including those undergoing endarterectomy, should receive aspirin. In all patients, there should be an aggressive effort to control risk factors for cardiovascular and cerebrovascular disease.