Effectiveness of MDCT angiography for the detection of intracranial aneurysms in patients with nontraumatic subarachnoid hemorrhage

OBJECTIVE. CT angiography (CTA) is a noninvasive imaging technique used to evaluate cerebral vascular structures. Digital subtraction angiography (DSA), although invasive, is the gold standard for diagnosing intracranial aneurysms. The purpose of this study was to evaluate the effectiveness of CTA in the detection of intracranial aneurysms for patients with nontraumatic subarachnoid hemorrhage (SAH) in a level 1 trauma center. MATERIALS AND METHODS. We evaluated the diagnostic accuracy of MDCT in 336 consecutive patients undergoing evaluation for nontraumatic SAH with both CTA and 3D DSA within 48 hours. The diagnostic performance of CTA was assessed by radiology reports using DSA as the gold standard. Analyses were performed per aneurysm and per patient, the results were stratified by aneurysm size and location, and the MDCT data - 16-MDCT data versus 4-, 8-, and 16-MDCT combined data - were compared. RESULTS. The overall sensitivity and specificity of CTA per aneurysm was 83% (CI, 0.78-0.87) and 93% (0.88-0.97), respectively. CTA failed to detect 49 of the 284 aneurysms. Thirty-nine (80%) of these 49 missed aneurysms were ≤ 3 mm, nine (18%) were 4-6 mm, and one (2%) was 7-10 mm. The sensitivity and specificity of CTA per patient was 95% (0.91-0.97) and 97% (0.92-0.99), respectively. Of 211 patients, a primary aneurysm was missed on CTA in 11 patients. CONCLUSION. CTA showed excellent diagnostic performance for aneurysm detection. The high negative predictive value (91.2%) for the per-patient analysis indicates that CTA has merit as a screening tool. Most aneurysms missed were ≤ 3 mm and in patients in whom a primary aneurysm had already been detected.