The diagnostic yield of repeat computed tomography angiography in cases of spontaneous subarachnoid haemorrhage after negative initial digital subtraction angiography

Purpose: It is currently unclear how useful repeat computed tomography angiography (CTA) is in spontaneous sub- arachnoid haemorrhage (SAH) patients after negative initial digital subtraction angiography (DSA). The purpose of this study is to assess the yield of repeat CTA for the detection of causative vascular lesions in patients with SAH in whom there has been a negative initial DSA. Material and methods: This observational retrospective study was carried out from January 2013 to July 2022 at a single institution. Analysis of the SAH pattern on unenhanced CT showed that patients were divided into perimesence- phalic SAH and diffuse SAH groups. A repeat CTA was performed on all spontaneous SAH patients who had a nega- tive initial CTA and DSA within a 2 -week period. An interventional neuroradiologist and a diagnostic radiologist examined all images to search for causative vascular abnormalities. Results: Forty-seven patients were included in our study, with a median age of 55 years and a range of 28-81 years. Thirty-seven had diffuse SAH (66%), and 16 had perimesencephalic SAH (34%). The repeat CTA revealed 2 causa- tive vascular lesions (a right PICA aneurysm and a mycotic aneurysm) in 2 separate patients (yield of 4.3%), both of whom had diffuse SAH (yield of 6.5%). In retrospect, none of these vascular lesions were evident in the initial CTA and DSA. No evidence of re -bleeding was observed in the follow-up period. Conclusions: It is beneficial to repeat CTA when evaluating patients with diffuse SAH who initially present with nega- tive initial DSA. For occult aneurysms, the diagnostic yield of the follow-up CTA is 6.5%.