Delayed cerebral ischemia (DCI) is a life-threatening complication after subarachnoid hemorrhage. There is a strong association between cerebral vessel narrowing and DCI. Alpha calcitonin gene-related peptide (αCGRP) is a potent vasodilator, which may be effective at reducing cerebral vessel narrowing after subarachnoid hemorrhage (SAH). Here, we report a meta-analysis of data from nine in vivo animal studies identified in a systematic review in which αCGRP was administered in SAH models. Our primary outcome was change in cerebral vessel diameter and the secondary outcome was change in neurobehavioral scores. There was a 40.8 ± 8.2% increase in cerebral vessel diameter in those animals treated with αCGRP compared with controls (p < 0.0005, 95% CI 23.7–57.9). Neurobehavioral scores were reported in four publications and showed a standardized mean difference of 1.31 in favor of αCGRP (CI −0.49 to 3.12). We conclude that αCGRP reduces cerebral vessel narrowing seen after SAH in animal studies but note that there is insufficient evidence to determine its effect on functional outcomes.

Aneurysmal subarachnoid haemorrhage (SAH) is a type of stroke causing up to 70% of patients to either die or be dependent on others at six months. Delayed cerebral ischaemia (DCI) is the most important cause of poor outcome after the initial injury. Oral nimodipine is the only pharmaceutical treatment with proven benefits and alternative therapies are needed. There are strong associations between DCI and cerebral vessel narrowing but interventions to treat DCI by improving vessel narrowing have been largely ineffective. Alpha‐calcitonin gene‐related peptide (αCGRP) is a potent microvascular vasodilator which may be effective in treating DCI by preventing cerebral vessel narrowing after SAH. This protocol outlines the methodology for a systematic review and meta‐analysis investigating the effect of αCGRP on cerebral vessel narrowing and neurological outcomes after SAH from in vivo animal studies.