CT angiography for the detection of cerebral vasospasm in patients with acute subarachnoid hemorrhage

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is the standard of reference for detecting cerebral vasospasm after subarachnoid hemorrhage (SAH). CT angiography (CTA) is a relatively recent method for depicting the intracranial arterial vasculature. The purpose of this study was to compare CTA and DSA in the detection and quantification of cerebral vasospasm. METHODS: Seventeen patients with SAH underwent initial CTA with or without DSA and follow-up CTA and DSA. The follow-up CTA and DSA studies were performed within 24 hours of each other and 5 to 10 days after SAH. Maximum intensity projection images were produced for each CTA. Six arterial locations were examined for spasm: the suprasellar internal carotid artery (ICA), the M1 and M2 segments of the middle cerebral artery, the A1 and A2 segments of the anterior cerebral artery, and the basilar artery. Vasospasm was categorized as none, mild (<30% luminal reduction), moderate (30% to 50% reduction), or severe (>50% reduction). RESULTS: The overall correlation between CTA and DSA was 0.757, but was better for proximal than distal locations (0.88-1.00 versus 0.152-0.446). Agreement between CTA and DSA was greater for no spasm (92%) and severe spasm (100%) than for mild (57%) or moderate (64.%) spasm. CTA was highly accurate for no spasm or severe spasm in proximal locations (96%, and 100%, respectively); it was less accurate (90% and 95%, respectively) for mild or moderate spasm in these locations. For distal locations, the accuracy for absent, mild, moderate, or severe spasm was 78%, 81%, 94%, and 100%, respectively. CONCLUSION: CTA is highly sensitive, specific, and accurate in detecting no spasm or severe cerebral vasospasm in proximal arterial locations; it is less accurate for detecting mild and moderate spasm in distal locations.