Inclusion Criteria- Age ≥16 years
- Acute neurological presentation with recurrent transient ischemic attacks (TIA) or cerebral infarction within 30 days of symptom onset
- Angiographic findings compatible with the diagnostic criteria for MMD or MMS (unilateral findings, bilateral distal internal carotid artery involvement without Moyamoya vessels, or presence of other causative factors)
- Significant decrease in basal perfusion and reservoir capacity on brain perfusion CT or Brain single photon emission computed tomography with acetazolamide (Diamox®) challenge (D-SPECT)
Exclusion Criteria- Definite presence of transdural collateral flow on cerebral angiography.
- Sufficient perfusion status via Willisian, leptomeningeal, or other collateral systems, as evaluated by multimodal imaging methods.
- > 30 days after symptom onset