Moyamoya Disease is a chronic cerebrovascular disorder characterized by the narrowing of specific blood vessels in the brain, particularly the internal carotid arteries. This narrowing, known as stenosis, leads to restricted blood flow due to thrombosis, or the formation of blood clots. In response to these blockages, the body attempts to develop collateral circulation; however, these newly formed vessels are often weak and prone to further complications, such as bleeding, aneurysm, or additional thrombosis.