Intracerebral platelet accumulation as evidence for embolization of carotid origin.

Arterio-arterial embolism of carotid origin is one major cause of cerebral ischemia. To evaluate the role of blood platelets in this process, In-111 labeled platelet scintigraphy was performed in a series of 250 patients. Of this number, one patient with an 80% carotid stenosis and a normal intracerebral angiogram suffered a transient ischemic attack (TIA) several hours after the injection of radiolabeled platelets. The scintigram showed a pathologic platelet accumulation in the symptomatic carotid area as well as in the ipsilateral brain hemisphere. The authors conclude that this scintigraphic finding of hemispheric platelet aggregates recorded directly after a clinically observed TIA, together with previous observations of retinal emboli after amaurosis fugax attacks, provides strong evidence for the arterio-arterial embolic mechanism of TIA.