Evaluation of platelet changes in completed ischemic stroke.

In a retrospective study we evaluated the platelet count in 45 patients mean age 73 +/- 9 years, with cerebral infarction (C.I.) documented by CT, and 45 age and sex-matched controls randomly selected. In 12 patients changes in platelet count were examined prospectively, starting from the acute event for 30 days. In the retrospective study the mean platelet count in C.I. was significantly lower than that found in controls: 260, 220 +/- 86,076/mm3 and 302, 422 +/- 65,747/mm3 (p less than 0.05) respectively. In the prospective study the mean count was 213,330 +/- 79,930/mm3. A progressive increase up to the 9-12th day was observed, achieving a mean of 305,630 +/- 83,470/mm3 (p less than 0.01), not statistically different from controls. The 40-45% decrease of platelet count shows that about half of the circulating platelets had rapidly disappeared from the systemic circulation, presumably related to an increase in vivo platelet activation and aggregation.