This multicenter prospective cohort study aims to compare the difference in the effects of medical treatment within 1 year between the two groups of ICAS patients divided hemodynamically by Magnetic Resonance Fractional Flow Reserve. PC MRA will be applied for FFR measurement. The primary outcome is the composite of ischemic stroke or death related to the qualifying artery territory for 1 year.

Inclusion Criteria:

1. Patients aged from 30 to 80 with symptomatic ICAS lesion in anterior circulation.
2. 50% to 99% stenosis (in accordance with modified WASID method) confirmed by DSA, CTA or MRA.
3. mRS 0-2 points
4. Informed of the study protocol and objectives.

Exclusion Criteria:

1. Previous endovascular treatment or surgery for cerebrovascular diseases
2. Large cerebral infarction (more than 1/2 MCA perfusion area) according to MRI
3. Combined with other neurological diseases, such as aneurysm, arteriovenous malformation, tumor, hydrocephalus, cerebral trauma, cerebral hemorrhage, multiple sclerosis, epilepsy and intracranial infection.
4. Pregnancy or in the preparation for pregnancy
5. Patients who cannot tolerate or do not allow MR screening, including metal implanting and claustrophobia
6. Contraindication for antiplatelet drugs or statins
7. Patients with severe dementia or mental disorders, who cannot cooperate with examination

Patients with symptomatic, moderate to severe stenosis of major arteries in intracranial anterior circulation. The stenosis degree is ≥ 50%, confirmed by imaging evidence, according to modified WASID criteria.