Moyamoya disease is a vasculo-occlusive disease involving the circle of Willis, typically the terminal ICA.
The term moyamoya disease should be reserved for an idiopathic, sometimes familial, condition, which leads to characteristic intracranial vascular changes. Numerous entities have been described which mimic the appearance, in which case the term moyamoya phenomenon, syndrome or pattern is used.
This article concerns itself with moyamoya disease. For a list of conditions that can mimic moyamoya please refer to the article on moyamoya syndrome, or the differential diagnosis list at the end of the article.
Moyamoya is a disease of children and young people, with a bi-modal age distribution 6:
- early childhood: peak ~4 years of age
- middle age: 30-40 years of age
The condition was initially described in Japanese patients, where it is still most common, in which 7-10% of cases are familial.
Presentation is to some degree age dependent.
Moyamoya affects the distal ICA and circle of Willis. Small abnormal net-like vessels proliferate giving the characteristic "puff of smoke" appearance on direct angiography. CTA and MRA is not always able to demonstrate this appearance on account of lower flow and spatial resolution.
Although classically described affecting the ICA, over 50% of patients also have involvement of the posterior cerebral arteries.
Collateral circulation forms from a number of sources:
- via the abnormal moyamoya vessels
- pial collaterals from less affected vessles (especially PCA): forming the so called ivy sign on contrast enhanced MRI
- transdural branches of the middle meningeal and other dural branches
Bypassing the occlusive segments is the aim of most surgical therapy.
In adults external carotid artery to middle cerebral artery (ECA-MCA) anastamoses can be performed as the vessles are larger. One of the surgical option is superficial temporal artery to middle cerebral artery (STA-MCA) bypass.
Encephaloduroarteriosynangiosis is the treatment of choice in pediatric patients as thier vessles are too small to allow direct anastomosis.
The term moyamoya comes from "a Japanese expression for something hazy just like a puff of cigarette smoke drifting in the air" was first described by Suzuki and Takaku in 1969 1.
A number conditions can lead to imaging appearances that are very similar to moyamoya disease. For a full list please refer to moyamoya syndrome:
- cranial radiotherapy
- connective tissue disorders
- haematological disorders
- 1. Suzuki J, Takaku A. Cerebrovascular "moyamoya" disease. Disease showing abnormal net-like vessels in base of brain. Arch. Neurol. 1969;20 (3): 288-99. doi:10.1001/archneur.1969.00480090076012 - Pubmed citation
- 2. Mugikura S, Takahashi S, Higano S et-al. The relationship between cerebral infarction and angiographic characteristics in childhood moyamoya disease. AJNR Am J Neuroradiol. 1999;20 (2): 336-43. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Yoon HK, Shin HJ, Chang YW. "Ivy sign" in childhood moyamoya disease: depiction on FLAIR and contrast-enhanced T1-weighted MR images. Radiology. 2002;223 (2): 384-9. doi:10.1148/radiol.2232011094 - Pubmed citation
- 4. Bruno A, Adams HP, Biller J et-al. Cerebral infarction due to moyamoya disease in young adults. Stroke. 1988;19 (7): 826-33. Stroke (abstract) - Pubmed citation
- 5. Hsu SW, Chaloupka JC, Fattal D. Rapidly progressive fatal bihemispheric infarction secondary to Moyamoya syndrome in association with Graves thyrotoxicosis. AJNR Am J Neuroradiol. 2006;27 (3): 643-7. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 6. Kornienko VN, Pronin IN. Diagnostic Neuroradiology. Springer Verlag. (2008) ISBN:3540756523. Read it at Google Books - Find it at Amazon
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