False subarachnoid hemorrhage in anoxic encephalopathy with brain swelling.

The authors present two comatose patients with brain swelling from anoxic encephalopathy. Nonenhanced computed tomography (CT) images showed increased density on the falx, on the tentorium, and in the basal cisterns, all of which falsely suggested subarachnoid hemorrhage. Autopsy in both patients failed to show subarachnoid hemorrhage. In rare circumstances, anoxic encephalopathy can mimic subarachnoid hemorrhage on nonenhanced CT.