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Moyamoya disease is a disease in which certain arteries in the brain are constricted. Blood flow is blocked by constriction and blood clots (thrombosis). A collateral circulation develops around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to bleeding, aneurysm and thrombosis. On conventional angiography, these collateral vessels have the appearance of a "puff of smoke" (described as "もやもや (moyamoya)" in Japanese). When moyamoya is diagnosed by itself, with no underlying correlational conditions, it is diagnosed as moyamoya disease. This is also the case when the arterial constriction and collateral circulation are bilateral. Moyamoya syndrome is unilateral arterial constriction, or occurs when one of the several specified conditions is also present. This may also be considered as moyamoya being secondary to the primary condition. Mainly, occlusion of the distal internal carotid artery occurs. On angiography, a "puff of smoke" appearance is seen, and the treatment of choice is surgical bypass. Presentation Patients usually present with TIA, ischemic/hemorrhagic stroke, or seizure. The age distribution is bimodal being either young adolescence or mid-forties. Cause About 10% of cases of moyamoya disease are familial, and some cases result from specific genetic mutations. Susceptibility to moyamoya disease-2 (MYMY2; 607151) is caused by variation in the RNF213 gene (613768) on the long arm of chromosome 17 (17q25). Moyamoya disease-5 (MYMY5; 614042) is caused by mutation in the ACTA2 gene (102620) on the long arm of chromosome 10 (10q23.3); and moyamoya disease-6 with achalasia (MYMY6; 615750) is caused by mutation in the GUCY1A3 gene (139396) on the long arm of chromosome 4 (4q32). Loci for the disorder have been mapped to the short arm of chromosome 3 (MYMY1) and the long arm of chromosome 8 (8q23) (MYMY3; 608796). 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. In the United States moyamoya has an incidence rate of 0.086 per 100,000. In Japan the overall incidence is higher (0.35 per 100,000). 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. These women frequently experience transient ischaemic attacks (TIA), cerebral hemorrhage, or may not experience any symptoms at all. They have a higher risk of recurrent stroke and may be experiencing a distinct underlying pathophysiology compared to patients from Japan. Moyamoya disease can be either congenital or acquired. 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. It is more common in women than in men, although about a third of those affected are male. Pathophysiology 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. This makes the blood leak out of the arteries, causing pressure to the brain and subsequent headaches. Over the last six decades since the disease was first described, pathogenesis of moyamoya disease remained elusive, although the gene ring finger protein 213 (RNF213) has been implicated. In September 2021, a south Indian researcher has proposed a pathbreaking theory on moyamoya pathogenesis. Coined the "Mechano-biological theory", the disease has a multifactorial pathogenesis. The authors provide a tangible explanation of the occurrence of moyamoya phenomenon in the idiopathic and syndromic variants of the disease. 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. Once it begins, the vascular occlusion tends to continue despite any known medical management. In some people this leads to transient ischemic attacks or repeated strokes with severe functional impairment or even death. In others, the blockage may not cause any symptoms. The disease causes constrictions primarily in the internal carotid artery, and often extends to the middle and anterior cerebral arteries, branches of the internal carotid artery inside the skull. When the internal carotid artery becomes completely blocked, the fine collateral circulation that it supplies is obliterated. Patients often survive on the collateral circulation from the back (posterior) of the circle of Willis, arising from the basilar artery. The arterial constrictions in moyamoya disease are unlike the constrictions in atherosclerosis. In atherosclerosis, the walls of arteries are damaged, leading to the deposition of fat and immune cells, and ultimately the accumulation of immune cells laden with fat. In moyamoya, the inner layer of the carotid artery proliferates within the arterial lumen. The artery also fills with blood clots, which may cause strokes. Moyamoya disease tends to affect adults in the third to fourth decade of life. In children it tends to cause strokes or seizures. In adults it tends to cause strokes or bleeding. The clinical features are strokes, recurrent transient ischemic attacks (TIAs), sensorimotor paralysis (numbness and paralysis of the extremities), convulsions and/or migraine-like headaches. Moreover, following a stroke, secondary bleeding may occur. Such bleeding, called hemorrhagic strokes, may also stem from rupture of the weak neovascular vessel walls. Diagnosis Cerebral angiography is the gold standard of diagnosing moyamoya disease and its progression. According to Suzuki's system, it can be classified into six stages: Stage 1 Narrowing of carotid fork Stage 2 Initiation of the moyamoya and dilatation of intracranial main arteries Stage 3 Intensification of the moyamoya and defects of the anterior cerebral artery and middle cerebral artery Stage 4 Minimization of the moyamoya and defects of the posterior cerebral artery Stage 5 Reduction of the moyamoya and development of external carotid artery collaterals Stage 6 Disappearance of the moyamoya and circulation only via external carotid artery and vertebral artery Magnetic resonance angiography (MRA) is also useful in diagnosing the disease with good correlation with Suzuki's grading system. Proliferation of smooth muscle cells in the walls of the moyamoya-affected arteries has been found to be representative of the disease. A study of six autopsies of six patients who died from moyamoya disease lead to the finding that there is evidence that supports the theory that there is a thickening, or proliferatio.... Discover the Sarah Lippett popular books. Find the top 100 most popular Sarah Lippett books.