Abstract 3282: Diagnostic Yield of Repeat CT Angiography in Patients with Subarachnoid Hemorrhage and Negative Initial CT and Catheter Angiograms

Purpose: To determine the yield of repeat CT angiography for the detection of causative vascular lesions in patients with subarachnoid hemorrhage (SAH) who have negative initial CT and catheter angiograms. Methods: We conducted a retrospective review of patients who presented to our institution between January 1st, 2008 and August 1st, 2011 with SAH and negative initial CT and catheter angiograms who were examined with repeat CT angiography in order to determine the yield of this imaging modality for the detection of causative vascular lesions. Two experienced neuroradiologists evaluated the NCCTs to determine the pattern of SAH (diffuse, perimesencephalic or peripheral) and the CT angiograms (CTA) to assess for the presence of a causative vascular lesion. All differences in reader interpretation were resolved by consensus. Results: Twenty-two patients were included in our study, with a mean age of 78 years (median 59 years, range 28-78 years). Sixteen patients were male (72.7%) and 6 female (27.3%). Seventeen patients had diffuse SAH (77.3%), 4 perimesencephalic SAH (18.2%) and 1 peripheral SAH (4.5%). Mean time interval between the initial neurovascular examination and the repeat CTA was 26.5 days (median 20.5 days, range 2-150 days). The repeat CTA demonstrated a causative vascular lesion in 2 patients (9.1%), all of which had diffuse SAH (yield of 11.8%). The vascular lesions identified were 1 small pontine arteriovenous malformation and a 2-mm supraclinoid internal carotid artery aneurysm ( Figure ). The pontine arteriovenous malformation underwent radiosurgery and the internal carotid artery aneurysm underwent surgical clipping. In retrospect, none of these vascular lesions were evident in the initial CT or catheter angiograms. Conclusion: Repeat CT angiography is valuable in the evaluation of patients with diffuse SAH who have negative initial CT and catheter angiograms, demonstrating a causative vascular lesion in 11.8% of patients.