Unifying Concepts

Guidelines for Diagnosis of Moyamoya Disease

Moyamoya disease is a cerebrovascular condition predisposing affected patients to stroke in association with progressive stenosis of the intracranial internal carotid arteries and their proximal branches.

1. Diagnostic criteria

(1) Cerebral angiography is indispensable for the diagnosis and should present at least the following findings:

1) Stenosis or occlusion at the terminal portion of the internal carotid artery and/or at the proximal portion of the anterior and/or the middle cerebral arteries.
2) Abnormal vascular networks in the vicinity of the occlusive or stenotic lesions in the arterial phase.
3) These findings should present bilaterally.

(2) When Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA) clearly demonstrate all the findings described below, conventional cerebral angiography is not mandatory.

1) Stenosis or occlusion at the terminal portion of the internal carotid artery and at the proximal portion of the anterior and middle cerebral arteries on MRA.
2) An abnormal vascular network in the basal ganglia on MRA. Note: An abnormal vascular network can be diagnosed when more than two apparent flow voids are seen in one side of the basal ganglia on MRI.
3) 1) and 2) are seen bilaterally. (Refer to the Image Diagnostic Guidelines by MRI and MRA.)

(3) Because the etiology of this disease is unknown, cerebrovascular disease with the following basic diseases or conditions should thus be eliminated:

1) arteriosclerosis
2) autoimmune disease
3) meningitis
4) brain neoplasm
5) Down syndrome
6) Recklinghausen’s
7) head trauma disease
8) irradiation to the head
9) others

(4) Instructive pathological findings:

1) Intimal thickening and the resulting stenosis or occlusion of the lumen are observed in and around the terminal portion of the internal carotid artery usually on both sides. Lipid deposits are occasionally seen in the proliferating intima.
2) Arteries constituting the circle of Willis such as the anterior and the middle cerebral and the posterior communicating arteries often show stenosis of various degrees or occlusion associated with fibrocellular thickening of the intima, a waving of the internal elastic lamina, and an attenuation of the media.
3) Numerous small vascular channels (perforators and anastomotic branches) are observed around the circle of Willis.
4) Reticular conglomerates of small vessels are often seen in the pia mater.

In reference to 1. mentioned above, the diagnostic criteria are classified as follows: Autopsy cases not undergoing cerebral angiography should be investigated separately while referring to (4).

1. Definite case
One that fulfills either (1) or (2), and (3). In children, however, a case that fulfills (3) and (1) 1) and 2) or (2) 1) and 2) on one side and with remarkable stenosis at the terminal portion of the internal carotid artery on the opposite side is also included.
2. Probable case
One that fulfills (1) 1) and 2) or (2) 1) and 2), and (3) (unilateral involvement)




  1. The Research Committee of Spontaneous Occlusion of the Circle of Willis (Moyamoya Disease) of the Ministry of Health and Welfare, Japan: Guidelines for diagnosis. Clin Neurol Neurosurg. 1997;99(suppl 2):S238–S240. [Medline]
  2. Scott RM, Smith ER. Moyamoya disease and moyamoya syndrome. N Engl J Med. 2009 Mar 19;360(12):1226-37. [Medline]


Created Mar 24, 2009

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