Brain computed tomography angiographic scans as the sole diagnostic examination for excluding aneurysms in patients with perimesencephalic subarachnoid hemorrhage

OBJECTIVE: In an era in which new computed tomographic scanners approach 100% sensitivity for finding intracranial aneurysms in patients with a perimesencephalic subarachnoid hemorrhage (SAH) pattern, digital subtraction angiography (DSA) is still considered the gold standard. Our purpose was to investigate whether or not computed tomography angiographic (CTA) scanning can be used as the sole diagnostic tool in this setting, and thus replace DSA. METHODS: Two hundred fifty patients with atraumatic SAH presented to our institute between November 2001 and November 2005. We performed a retrospective search for those patients who had a negative brain CTA scan for aneurysms. Of these, those with a computed tomographic scan showing perimesencephalic SAH at admission were selected, and only those who had DSA performed were included. RESULTS: We found 30 patients with negative brain CTA scans that matched the perimesencephalic SAH pattern and had DSA performed. The mean time for performing a brain CTA scan was 3.8 +/- 4.4 days, and for DSA 11 +/- 12 days, after the initiation of symptomatology. The interval between CTA and DSA was 5.9 +/- 15 days. There were two patients in whom CTA was considered negative but still suspicious for having an aneurysm; DSA was negative for both. CONCLUSION: Brain CTA scanning alone is a good and conclusive diagnostic tool to rule out aneurysms in patients presenting with the classic perimesencephalic SAH pattern and thus can replace DSA and its corresponding risks. The latter can be reserved for those patients in whom CTA is doubtful.