To elucidate platelet activation in cerebral circulation and its significance in ischemic stroke, the plasma beta-thromboglobulin (BTG) concentration gradients between the internal jugular vein and the antecubital vein were investigated in 164 patients with ischemic stroke. They consisted of cases of lacunar, atherothrombotic, cardioembolic stroke, and Binswanger's disease. The diagnosis of each stroke category was based on both computed tomographic (CT) and clinical findings. In particular, Binswanger's disease was diagnosed by the diagnostic criteria proposed by Bennett et al. Blood was withdrawn simultaneously from the internal jugular vein (A) and the antecubital vein (B) followed by determination of the BTG-A level and the BTG-B level, respectively. The BTG levels of 184 paired blood samples, thus, were obtained and the ratio (delta BTG) of BTG-A/BTG-B was calculated as an indicator for platelet activation in the cerebral circulation. According to the timing of the examination, these values of the acute phase less than 7 days after the event were separated from those of the chronic phase more than 28 days after the event. The delta BTG levels were also determined in 25 of controls with diseases other than stroke and considered to reflect platelet activation in the cerebral circulation. The mean delta BTG values of each stroke subtype without ticlopidine treatment, compared with those of controls (0.96 +/- 0.42), were significantly higher except those during the chronic phase of cardioembolic stroke and pronounced variability of delta BTG was noted in most subtypes.(ABSTRACT TRUNCATED AT 250 WORDS)