[Two cases of ischemic stroke due to low protein C caused by severe hyperthyroidism].

We reported two patients with acute ischemic stroke who had presented with symptoms of thyroid storm. Case1: A 43-year-old man abruptly developed left hemiparesis caused by the right middle cerebral artery occlusion. Cardiac evaluations revealed atrial fibrillation and left atrial enlargement. He had successful recanalization after reperfusion therapies. Case 2: A 66-year-old woman with severe bilateral middle cerebral artery stenosis presented with right hemiparesis and dysarthria. MRI revealed the acute infarction in the left frontal and parietal lobe. In both cases, protein C activity was decreased which could be related to severe hyperthyroidism. They concomitantly had arterial lesions where blood stasis could occur. Severe hyperthyroidism which could evoke the decreasing of protein C activity could be responsible to develop acute ischemic stroke.