Purpose: CTA is becoming the frontline modality to reveal aneurysms in patients with SAH. However, in about 20% of SAH patients no aneurysm is found. In these cases, intra-arterial DSA is still performed. Our aim was to evaluate whether negative findings on CTA can reliably exclude aneurysms in patients with acute SAH. Materials and Method: We conducted a retrospective analysis of all DSA performed from August 2010 to July 2014 in patients with various indications. We selected patient who presented with SAH and had a negative CTA. Findings of the CTA were compared with DSA. Results: 857 DSA were performed during the study period. 51(5.95%) patients with SAH and negative findings on CTA who underwent subsequent DSA were identified. Of these, only 3(5.9%) of patients had positive findings on the DSA. One patient had a posterior inferior cerebellar artery aneurysm on the DSA, not seen on CTA due to the incomplete coverage of the head. Second patient’ CTA did not show any evidence of aneurysm. DSA showed suspicious dissection of the right vertebral artery, potentially iatrogenic. The third patient’s DSA showed suspicious tiny protuberance from left ICA, possibly infundibulum. Conclusion: In patients with SAH, negative CTA findings are reliable in ruling out aneurysms in any pattern of SAH on CT.
"Infra-Posterior Inferior Cerebellar Artery Aneurysm" Arising After Occlusion of the Ipsilateral Vertebral Artery. Case Report.