Table 1. Diagnostic criteria and their limitations in adult MMD.

Diagnostic criteria	Limitations in adults
1. Steno-occlusive lesions around terminal portions of the ICA.	Stenosis of the distal intracranial ICA and tandem stenosis of the proximal ACA and MCA may not be observed in the early stages of MMD (Fig 2).
2. Moyamoya vessels at the base of the brain appearing as abnormal vascular networks on conventional angiography or MR angiography.	No objective criteria for ‘prominent’ basal collateral vessels.
	Less prominent basal collaterals in adult MMD than childhood MMD
3. Findings 1 and 2 are present bilaterally (definite MMD according to diagnostic criteria).	Contralateral disease develops in up to 40% of patients with unilateral MMD.[33] [34] [35] (Fig 2)
4. Exclusion of known disease with similar angiographic findings (arteriosclerosis, autoimmune disease, meningitis, brain neoplasm, Down syndrome, neurofibromatosis type 1, head trauma, head irradiation, and protein C or S deficiency).	Relatively common steno-occlusive diseases causing ‘Moyamoya syndrome’ (e.g., intracranial atherosclerosis) in adults.