Repeated episodes of ischemic stroke over a short period in a patient with essential thrombocythemia on anticoagulant therapy.

A 69-year-old man who had essential thrombocythemia, for which he was taking no medications, suddenly developed aphasia and right hemiplegia and was admitted to the hospital. He was thought to have had an embolic stroke and was initially treated with warfarin. Although the international normalized ratio was in the therapeutic range, he had 3 additional ischemic stroke episodes with the same symptoms after the index stroke. Magnetic resonance angiographic examinations revealed serial changes in middle cerebral artery stenosis. After administration of an antiplatelet agent and hydroxyurea, he had no additional strokes.