Thrombosed Giant Aneurysm with Unusual Neuroimaging Features Mimicking Pseudoaneurysm.

A 76-year-old man who had suffered subarachnoid hemorrhage about 10 years ago did not undergo surgery but other details were not clear. When admitted to our hospital, his consciousness level was 3-1-5 (Glasgow coma scale) and right hemiparesis was apparent. In the computed tomography (CT) scan, a cerebral hematoma (64×43×60mm) and subarachnoid hemorrhage appeared in the left frontotemporal area and a circular low-density area was observed in the cerebral hematoma. Enhanced CT enhanced the low-density area. In magnetic resonance (MR) and cerebral angiography, a cerebral aneurysm (8×7×7mm) was observed at the bifurcation of the M1-M2 and cystic expansion (17×13×15mm) adjoined the aneurysm. We considered pseudoaneurysm or thrombosed giant aneurysm. We conducted coil embolization of the aneurysm using Guglielmi electrolytically detachable coils, then evacuated cerebral hematoma by stereotactic aspiration surgery. V-P shunt was conducted for normal pressure hydrocephalus after 23 days. Follow-up MRI and cerebral angiography showed thrombosis of aneurysm and disappearance of the cerebral hematoma. We discuss neuroimaging features of the giant aneurysm and pseudoaneurysm.