Angiogram negative subarachnoid haemorrhage: outcomes and the role of repeat angiography.

Background: Angiogram negative sub-arachnoid haemorrhage (SAH) is generally considered to have a more benign course than SAH of known cause. There is also variability from centre to centre as to what proportion of angiogram negative SAH patients undergo repeat Digital Subtraction Angiography (DSA). We performed a retrospective study looking at the last four years' of SAH patients at our institution in order to ascertain the clinical course, the nature and results of repeat imaging.

Methods: Retrospective analysis of clinical records and imaging of all patients presenting to our institution with non-traumatic SAH between April 2008 and February 2012 was performed. Results were analysed for presenting grades, blood distribution, complications, outcomes, repeat imaging modalities and findings.

Results: 459 patients with proven non-traumatic SAH of which 50 (11%) had no vascular cause identified on their initial angiogram were identified. The blood distribution was perimesencephalic in 17, non-perimesencephalic in 23, and 10 patients were computed tomography (CT) Negative with a positive lumbar puncture. Eight (16%) patients were complicated by hydrocephalus and 2 (4%) were complicated by vasospasm. Eight patients (16%) underwent repeat cranial DSA with a high suspicion in a multi-disciplinary team setting. None of the repeat angiograms showed an underlying aetiology for the SAH. 76% of patients had a Glasgow Outcome Score of 5 at 6 months. There were no rebleeds.

Conclusions: While generally more benign, angiogram negative subarachnoid haemorrhage can have a complicated clinical course. In our experience repeat DSA should be reserved for cases in which there is significant suspicion of occult vascular lesion. However, evidence-based guidelines are needed to aid the development of management protocols for angiogram-negative SAH and ensuring optimal patient outcomes.