Haemorrhage pattern and clinical outcomes after angiogram negative subarachnoid haemorrhage: a systematic review and...

Angiogram-negative subarachnoid haemorrhage accounts for approximately 15% of spontaneous subarachnoid haemorrhage, yet surveillance practices and the role of repeat vascular imaging remain inconsistent. The extent to which haemorrhage pattern predicts clinical complications and delayed vascular lesion detection is uncertain.

We conducted a systematic review and meta-analysis in accordance with PRISMA guidelines. Studies reporting clinical outcomes in angiogram-negative subarachnoid haemorrhage were included. Outcomes were pooled using random-effects generalised linear mixed models and stratified by haemorrhage pattern, including perimesencephalic, non-perimesencephalic, diffuse, and convexity haemorrhage.

Sixty-seven studies comprising 5,921 patients were included. Favourable functional outcome at 3-6 months occurred in 95-97% of patients across all haemorrhage patterns. Rebleeding was uncommon, occurring in 1% of perimesencephalic, 2% of non-perimesencephalic, and 3% of diffuse haemorrhage. Clinical vasospasm occurred in 3%, 11%, and 13%, respectively, while acute hydrocephalus requiring external ventricular drainage occurred in 7%, 29%, and 44%. Among studies reporting repeat vascular imaging, 82 vascular lesions were identified, predominantly in non-perimesencephalic haemorrhage. No lesions were detected on imaging performed within 7 days of ictus; all reported lesions were identified at or beyond 7 days, although repeat imaging was selectively performed and timing varied across studies.

Angiogram-negative subarachnoid haemorrhage is clinically heterogeneous. Haemorrhage pattern is associated with distinct complication profiles and differential observed yields of delayed vascular lesion detection, and may assist in individualising surveillance strategies. Prospective studies are required to define optimal imaging intervals.