Fig. 4

Changes in the blood vessel wall after subarachnoid hemorrhage (SAH). Cerebral vasospasm often manifests on the third day following SAH. Cerebral vasospasm may initiate with smooth muscle contraction, and later, various factors such as oxidative stress, inflammation, and shear stress may disrupt the balance between extracellular matrix protein hydrolysing enzymes and their endogenous tissue inhibitors, leading to increased collagen cross-linking, collagen deposition, and elastic protein degradation in the arterial wall, resulting in arterial wall stiffness. The breakdown of elastic protein also leads to vascular smooth muscle cell proliferation, contributing to further luminal vessel narrowing