Transient CT hyperattenuation after Merci clot retrieval and intraarterial thrombolysis in acute stroke mimicking subarachnoid hemorrhage.

Unenhanced computed tomography (CT) revealed hyperattenuating lesions in two patients with acute stroke immediately after clot retrieval with the Merci device in one patient and after intraarterial thrombolysis in the other. These areas of hyperattenuation were noted in the middle cerebral artery territory in the first patient and involving the brainstem, cerebellum, and tentorium in the second. Both were falsely interpreted as subarachnoid hemorrhage. The area of hyperattenuation resolved within a few hours in both patients, reflecting contrast medium extravasation/leakage. This report highlights the need to improve physician skill in recognizing contrast medium extravasation that is common following neuroendovascular procedures, which are becoming commonplace in modern day medicine.