Alpha Calcitonin Gene-Related Peptide increases Cerebral vessel Diameter in Animal Modelsof Subarachnoid Hemorrhage: A Systematic Review and Metaanalysis

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 (alpha CGRP) 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 alpha CGRP 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 alpha CGRP 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 alpha CGRP (CI -0.49 to 3.12). We conclude that alpha CGRP reduces cerebral vessel narrowing seen after SAH in animal studies but note that there is insufficient evidence to determine its effect on functional outcomes.