See also MYMY4 (300845), an X-linked recessive syndromic disorder characterized by moyamoya disease, short stature, hypergonadotropic hypogonadism, and facial dysmorphism, and linked to q25.3, on chromosome 17.

[8] In North America, women in the third or fourth decade of life are most often affected, but the condition may also occur during infancy or childhood.

Patients with Down syndrome, sickle cell anemia, neurofibromatosis type 1, congenital heart disease, fibromuscular dysplasia, activated protein C resistance, or head trauma can develop moyamoya malformations.

[11] The disease moyamoya, which is a Japanese mimetic word, gets its characteristic name due to the appearance of smoke on relevant angiographs resultant from the tangle of tiny vessels in response to stenosis.

The authors provide a tangible explanation of the occurrence of moyamoya phenomenon in the idiopathic and syndromic variants of the disease.

[13] In short, the authors report that moyamoya disease likely occurs due to a number of factors (e.g., differences in vascular anatomy) that ultimately contribute to broad cerebral blood vessel occlusion and consequent shifts in vessel connections to try to provide blood for the compromised brain.

[16] Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease.

Conventional angiography provides the conclusive diagnosis of moyamoya disease in most cases and should be performed before any surgical considerations.

These biomarkers of moyamoya are "stenosis of the distal ICA's up to and including the bifurcation, along with segments of the proximal ACA and MCA...dilated basal collateral vessels must be present" [20] Some other common findings that have not been added to the classification index of those with moyamoya disease which are found using radiography involve very distinct changes in the vessels of the brain.

Functional changes include evidence of ischemia in vessels of the brain (ICA, ACA, MCA, specifically).

[20] This recently changed in 2021 as the Research Committee of Moyamoya Disease (RCMD) has "removed limitations of the previous definition that required bilateral involvement of the intracranial carotid artery.

[20] Other studies have confirmed the correlation of moyamoya and adhesion molecule 1 (ICAM-1) being increased as compared to normal vascular function counterparts.

[22][23] Furthermore, it has been concluded that the localization of inflammatory cells suggests that the inflammation stimulus itself may be responsible for the proliferation and occlusion in the ICA, ACA, and MCA found in those with moyamoya disease.

Although its efficacy, particularly for hemorrhagic disease, remains uncertain, the procedure is thought to reduce the hemodynamic burden on the engorged collateral blood vessels.

[citation needed] In the EMS (encephalomyosynangiosis) procedure, the temporalis muscle, which is in the temple region of the forehead, is dissected and through an opening in the skull placed onto the surface of the brain.

The modified direct anastomosis and encephalo-myo-arterio-synangiosis play a role in this improvement by increasing cerebral blood flow (CBF) after the operation.

[24] Although symptoms may seem to improve almost immediately after the in-direct EDAS, EMS, and multiple burr holes surgeries, it will take probably 6 to 12 months before new vessels can develop to give a sufficient blood supply.

[citation needed] Once a major stroke or bleeding takes place, even with treatment, the patient may be left with permanent loss of function so it is very important to treat this condition promptly.

[citation needed] In June 2008, a case report established that both moyamoya disease and arteriovenous fistulas (AVFs) of the lining of the brain, the dura, are associated with dural angiogenesis.

At least one case of simultaneous unilateral moyamoya syndrome and ipsilateral dural arteriovenous fistula has been reported at the Barrow Neurological Institute.

Cerebral angiography showed a right moyamoya pattern and an ipsilateral dural AVF fed by branches of the external carotid artery and draining into the transverse sinus.

A research group in southern India have proposed this unifying theory based on computational fluid dynamics studies and longitudinal data.