Moyamoya disease

meaning 'puff of smoke' in Japanese, a term used to describe the appearance of multiple collateral vessels, usually lenticulostriate and thalamostriate vessels, seen on cerebral angiography in patients with a vasculopathy characterised by progressive stenosis of the distal internal carotid arteries and the major intracranial arteries. The posterior circulation is less commonly involved. Though the condition is seen in adults 50% of reported cases of moya-moya syndrome occur in patients under 10 years, with 70% under 20% years. Patients usually present with transient ischaemic attacks, headache or seizures. Familial cases of the condition have been reported in Japan. The condition may also be seen in patients with phakomatosis, such as neurofibromatosis type 1 and tuberous sclerosis, Downs syndrome, following radiation therapy, polyarteritis nodosa and Takayasus arteritis, and sickle cell diseases. When no cause is found the condition is known as moya-moya disease. The definitive diagnosis is made on cerebral angiography where stenoses in the distal internal carotid and intracranial circulation are seen in association with multiple small collateral vessels in the region of the thalamostriate and lenticulostriate arteries.

MRI may make the diagnosis though the number of collaterals and the extent of disease may be underestimated. Areas of focal infarction both acute, subacute and chronic, may be evident on both CT and MRI. After intravenous contrast administration intense enhancement may be seen in the deep grey nuclei either from infarction or enhancement of the collateral vessels. Enlargement of the perivascular spaces (VirchowRobin) spaces with enhancement of the collateral vessels within them may also be seen on MRI. Prognosis is variable and may be worse if there is a pre-existing condition. The idiopathic form may not progress. The creation of external carotid to internal carotid anastamoses has been used to bypass the strictured areas.

EP