Moyamoya disease is a rare idiopathic steno-occlusive disease of the internal carotid arteries resulting in collateralization from new fragile vessels at the base of the brain termed “moyamoya” vessels. It most commonly affects patients of Asian descent, but has been observed in all ethnic groups. The age of onset fits a bimodal distribution in the 5–9- and 40–44-year age groups. MMD most often presents with stroke-like symptoms in children and bleeding in adults. The treatment for MMD involves revascularization surgery to replenish blood flow to the diseased areas of the brain. Revascularization can be performed by “direct” bypass where an external vessel is anastomosed to a brain vessel to replenish flow immediately or by “indirect” means where a vascular donor tissue is surgically planted on or near the surface of the brain to encourage formation of new vasculature. Outcomes for moyamoya are favorable with revascularization surgery showing decreased rates of stroke reported in patients after successful revascularization.
Digital subtraction angiogram and right sided stroke in a patient with Moyamoya disease
Typically a direct “brain” bypass is done for a patient with Moyamoya disease. This is usually performed in patient above the ago of 10 years as the blood vessels are of good size to perform the bypass. Other indications for bypass include severe extracranial or intracranial atherosclerotic blood vessel disease, bypass performed as part treatment for tumours or blood vessel aneurysms at the skull base
Schematic representation of a direct brain bypass procedure
Actual images of a direct brain bypass surgery.
STA-MCA bypass final picture
Angiogram at 6 months follow-up showing good blood supply to the brain from the bypass
Indirect bypass is done in patients with blood vessels which are too small to perform a direct bypass and also in patients who have failed a previous direct bypass. In this case, the superficial temporal artery and scalp muscle is placed over the brain to develop connections over a period of 6 months.
