Positional transient loss of consciousness and hemispheric deficits in the setting of severe four-vessel extracranial cerebrovascular disease.

Carotid artery stenosis typically causes hemispheric neurologic effects by atheroembolism. Nonhemispheric symptoms, such as syncope, are generally not attributable to extracranial carotid disease. This report describes a 62-year-old woman with severe bilateral carotid artery stenosis, right vertebral artery occlusion, and severe left vertebral artery stenosis who presented with transient loss of consciousness and unilateral weakness when upright. Her symptoms resolved after right carotid endarterectomy. Whereas vertebrobasilar insufficiency alone can cause syncope, in the case of severe multivessel cerebrovascular disease, unilateral carotid revascularization was successful in treating the patient's transient loss of consciousness, suggesting global cerebral hypoperfusion as the cause.