Second, focal cerebral ischemia may stimulate collateral growth via the secretion of cytokines, such as angiogenic peptides21 and vascular endothelial growth factor (VEGF).22 Some studies have shown that VEGF levels are lower in aged individuals than in young individuals.23 Third, common concomitant diseases in adult MMD patients, such as hypertension, have been shown to affect the development of collaterals in rats.24 This evidence concerns the gene VEGFA and hypertensive disorder.