The emergency department incidence of incidental intracranial aneurysm on computed tomography angiography (EPIC-ACT) study.

Background: Subarachnoid hemorrhage has been traditionally ruled-out in the emergency department (ED) through computed tomography (CT) followed by lumbar puncture if indicated. Mounting evidence suggests that non-contrast CT with CT angiography (CTA) can safely rule-out subarachnoid hemorrhage and obviate the need for lumbar puncture, but adoption of this approach is hindered by concerns of identifying incidental aneurysms. This study aims to estimate the incidence of incidental aneurysms identified on CTA head and neck in an ED population.

Methods: This was a health records review of all patients ≥ 18 years who underwent CTA head and neck for any indication at four large urban tertiary care EDs over a 3 month period. Patients were excluded if they underwent CT venogram only, had previously documented intracranial aneurysms, or had intracranial hemorrhage with or without aneurysm. Imaging reports were reviewed by two independent physicians before extracting relevant demographic (age, sex), clinical (CTAS level, CEDIS primary complaint) and radiographic (number, size, and location of aneurysms) information. The incidence rate of incidental aneurysms was calculated.

Results: A total of 1089 CTA studies were reviewed with a 3.3% (95% CI 2.3-4.6) incidence of incidental intracranial aneurysms. The median size of incidental aneurysms was 4 mm (0.7-11) and 10 (27.7%) patients had multiple aneurysms. Patients with incidental aneurysms did not differ based on mean age, sex, and CTAS levels.

Conclusions: The "risk" of discovering an incidental aneurysm is 3.3%. Clinicians should not be deterred from using CTA in the appropriate clinical settings. These estimates can inform shared decision-making conversations with patients when comparing subarachnoid hemorrhage rule-out options.