Incidence, predictors, and clinical outcome of patients with undetected aneurysms on initial DSA after aneurysmal subarachnoid hemorrhage.

Introduction: Digital subtraction angiography (DSA) is the gold standard for diagnosing ruptured intracranial aneurysms in aneurysmal subarachnoid hemorrhage (aSAH). However, aneurysms may occasionally remain undetected on initial DSA, potentially delaying treatment and increasing the risk of rebleeding. The primary aim was the incidence of aneurysms missed on initial DSA; secondary aims were characteristics, diagnostic yield and outcome. Material and methods: We retrospectively analyzed patients with aSAH treated between March 2006 and October 2023 with initial negative DSA. Demographic, clinical and radiological characteristics were assessed. Neurological outcomes were evaluated using the Glasgow Outcome Scale and modified Rankin Scale and compared with a matched cohort of patients with immediate aneurysm detection. Results: Among 1221 patients with aSAH, 14 (1.1%) had initially negative DSA findings with subsequent aneurysm detection. Repeat DSA identified the aneurysm in eight patients (57.1%). MRI was performed in 13 patients and contributed to aneurysm detection in three cases (21.4%). A third DSA revealed aneurysms in two additional patients (14.3%), while one aneurysm was identified during surgical exploration. The mean interval between initial and repeat diagnostics was five days (range 1-14). Rebleeding occurred in three patients (21.4%) before aneurysm diagnosis. Delayed-detection aneurysms were significantly smaller than aneurysms identified on initial DSA (1.8 mm vs. 6.7 mm, p < 0.05). Discussion and conclusion: Ruptured aneurysms may be missed on initial DSA, particularly when small. Repeat DSA, complemented by MRI when appropriate, should be performed during the same hospital stay, even in perimesencephalic hemorrhage patterns, to avoid delayed treatment and adverse outcomes.