Intracranial atherosclerotic stenosis (ICAS) carries substantial stroke risk despite optimal medical treatment. Current risk stratification relies primarily on stenosis severity, but novel hemodynamic markers may improve prediction. In this multiple prospective registry study we aim to investigate whether regional hemodynamics, measured by a novel Magnetic resonance imaging-derived Pressure Ratio (MPR) technique, are associated with stroke risk in ICAS.

This study is a multicentre prospective single-arm registry study and the protocol is approved by the ethics committee at the coordinating centre and by the local institutional review board at each participating centre. This study is initiated by the investigators, with 5 participating stroke centres , and plans to recruit 400 consecutive patients who meet the inclusion and exclusion criteria. After the enrolment, all participants would be evaluated at baseline, 1 month, 6 months, and 12 months post-enrollment. All participants received standardized medical therapy, including dual antiplatelet treatment and management of vascular risk factors, in accordance with AHA/ASA guidelines. Multimodal imaging techniques were employed to assess hemodynamic status: luminal stenosis would be evaluated using transcranial Doppler (TCD), computed tomography angiography (CTA), magnetic resonance angiography (MRA), or digital subtraction angiography (DSA), high-resolution MRI and phase-contrast MR angiography (PC-MRA) would be collected to calculate MPR. The primary outcomes were ischemic stroke in the qualifying artery territory or related death within 1 year. There were 5 secondary outcomes, including hemodynamic ischemic stroke in the qualifying artery territory within1 year. An independent Data and Safety Monitoring Board (DSMB) oversees the conduction, safety and efficacy of the study.

Inclusion Criteria:

1. Adults aged 18 to 80 years.
2. Intracranial atherosclerotic stenosis ICAS involving a culprit artery in the anterior circulation.
3. Intracranial arterial stenosis of 50% to 99% as measured by the WASID method using TCD, CTA, MRA, or DSA.
4. Written informed consent obtained from the participant or a legal representative.

Exclusion Criteria:

1. Non-atherosclerotic intracranial lesions, including moyamoya disease, vasculitis, vascular dissection, autoimmune diseases, or congenital/genetic abnormalities.
2. More than 50% stenosis of the extracranial carotid artery on the ipsilateral side.
3. Large cerebral infarction involving more than one-half of the territory on DWI imaging, or a baseline modified Rankin Scale score ≥3.
4. Contraindications to antiplatelet therapy or statins.
5. Inability to undergo MRI due to metal implants or claustrophobia.

Patients with ICAS involving 50% to 99% stenosis of a major intracranial artery in the anterior circulation, including the internal carotid artery (ICA C6-C7 segment) and the middle cerebral artery M1 (MCA-M1) segment.