Progressive stroke due to essential thrombocythemia.

We report a case of progressive stroke, due to an intracranial thrombosis, leading to a high-grade stenosis of the internal carotid artery (ICA). Essential thrombocythemia (ET) was identified as the cause of thrombosis. Effective anticoagulation in the acute phase of cerebral ischemia prevented further thrombus organization and total vessel obstruction. After clinical improvement and normalization of platelet counts under hydroxyurea, anticoagulation was stopped and antiplatelet agents were subsequently administered.