Introduction: Computerized tomography angiography (CTA) is commonly used to diagnose intracranial aneurysms with reported sensitivities as high as 97-100%. Despite improvements in CTA, digital subtraction angiography (DSA) remains the gold standard for ruptured aneurysms. Studies validating CTA accuracy in ruptured aneurysms in the setting of subarachnoid hemorrhage (SAH) are scarce, and limited by small sample sizes. This study evaluated the diagnostic accuracy of CTA to detect intracranial aneurysms in the setting of SAH.
Methods: A single-center retrospective cohort of 643 SAH patients was reviewed. A total of 407 patients were identified whose diagnostic workup included both CTA and confirmatory DSA. A comparative analysis between CTA and DSA findings was conducted. Aneurysms missed by CTA but diagnosed by DSA were further stratified by size and location.
Results: While CTA identified 338 aneurysms, DSA detected a total of 443 aneurysms. False positive CTA results (n=22) were seen in 20 patients. Additionally, DSA identified 127 aneurysms in 80 patients that were missed by CTA. Of the aneurysms missed by CTA, 83.6% were determined to be very small (<5mm), three quarters of which were smaller than 3mm. The supraclinoid internal carotid artery (ICA) harbored 42% of all missed aneurysms. The sensitivity of CTA was equal to 34.0% for aneurysms smaller than 3mm in size, and 59.6% for aneurysms originating from the ICA. The overall sensitivity of CTA in the detection of aneurysms in the setting of SAH was found to be 70.8% per patient, and 71.3% per aneurysm.
Conclusions: The accuracy of CTA in the diagnosis of intracranial aneurysm in the setting of SAH may be lower than previously reported. CTA has a low sensitivity for aneurysms smaller than 5mm, and in locations adjacent to bony structures. In addition, we conclude that CTA is not 100% sensitive for the detection of ruptured aneurysms.
Patient Care: Clinical decision-making in ruptured aneurysm patients is often based on CTA findings. Use of CTA alone may result in inaccurate identification of the bleeding source and could lead to devastating consequences if the unrecognized ruptured aneurysm is left untreated.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the limitations of CTA in diagnosing ruptured intracranial aneurysms
2) Discuss the sensitivity of CTA for diagnosing ruptured aneurysms according to size
3) Compare the accuracy of CTA with that of DSA for diagnosis ruptured aneurysms