Platelet activity and stroke severity.

Although platelets constitute the major component of a thrombus, its role in determining the clinical severity of thrombotic stroke is unknown. Therefore, we investigated the relationship between platelet ionized calcium ([Ca2+i]), a measure of platelet activity and presumably proneness to thrombosis, and clinical stroke severity in 45 consecutively studied acute ischemic stroke patients. Even though there was no correlation between the clinical neurological scores and the levels of baseline and activated platelet [Ca2+i], stroke was less severe in patients who had been taking aspirin at the time of stroke onset. These results raise several important questions: (a) is the extent of platelet activation a reflection of thrombus volume, (b) does the clinical severity of neurological deficit reflect the causative thrombus volume, and (c) whether the beneficial effect of aspirin in stroke prophylaxis is through its inhibition of platelets alone.