Moyamoya disease is an angiogenic disease caused by progressive stenosis of the cerebral arteries located at the base of the brain. It affects the intracerebral part of the internal carotids and causes a secondary collateral network to develop following a pattern resembling cigarette smoke ('moya-moya' in Japanese).
This disease remains asymptomatic in many cases: radiological criteria are observed in the absence of clinical signs in 1/2,000 adults in Japan, whereas the prevalence of Moyamoya syndrome is 1/32,000 in the general Japanese population. It is ten times less frequent in Europe.
Spontaneous progression may be insidious with headaches, epileptic seizures, language disorders and upper cerebral dysfunction. More often, acute and focal signs such as hemiplegia and sometimes hemichorea occur. Repeated deficiencies and frequently alternating hemiplegia represent the usual picture. Episodes are precipitated by hyperpnoea. The clinical picture can vary according to age, adults more often suffer from hemorrhages and children from ischemic accidents.
Moyamoya disease may be secondary to a known cause (drepanocytic anemia, radiotherapy, or in some patients affected by neurofibromatosis type I or William's syndrome; see these terms), or idiopathic. Hereditary forms of the disease, following an autosomal recessive pattern of transmission, have been described in about 10% of the cases. Various genetic localizations (chromosomes 3, 6, 8 and 17) have been reported in these familial forms.
The diagnosis is suggested by brain scans and magnetic resonance images showing multiple ischemic accidents of different ages, possibly hemorrhage and abnormal vessels at the base of the brain. Conventional angiography is used to ascertain the diagnosis and to assess the stage of evolution of the disease.
A variety of surgical techniques that stimulate peripheral angiogenesis can be proposed to compensate for deep ischemia. Treatment should begin early in the disease course to prevent vascular stenoses from affecting brain parenchyma.
Mortality rates are increased, especially by the occurrence of hemorrhagic accidents.
- Pr Josette MANCINI