Stroke has become the leading cause of death in China. It has been shown that intracranial artery stenosis (ICAS) plays a key role in Chinese stroke patients. Although most of stenotic diseases in intracranial arteries are atherosclerotic, a substantial number of other vascular diseases, such as dissection, arteritis, moyamoya disease, and reversible cerebral vasoconstriction syndrome (RCVS), can also lead to intracranial artery luminal narrowing. It is challenging to differentiate the etiologies of ICAS relying on measuring luminal narrowing by angiographical approaches. In addition, the progression of intracranial atherosclerotic disease (ICAD) has been demonstrated to be highly associated with the risk of ischemic cerebrovascular events. However, the influence factors for ICAD progression remains unclear.

High-resolution magnetic resonance imaging (HR-MRI) has been widely used to assess ICAS diseases. The different etiologies of ICAS are differentiable by MR-MRI according to the features of location, shape, signal pattern, remodeling, and contrast enhancement. Investigators have proved that HR-MRI is a reproducible technique that may be reliably utilized to monitor the changes of ICAD during natural follow-up or medical treatment.

The ICASMAP (Intracranial Artery Stenosis MR Imaging: Aetiology and Progression) is a prospective, cross-sectional, observational, and multicenter study. The objectives of ICASMAP are to determine: 1) the spectrum of etiology of ICAS in stroke patients; and 2) the influence factors for progression of ICAD. A total of 300 patients with symptomatic stenotic disease in intracranial arteries (stenosis range: 30%-99%) will be recruited within two weeks after symptom onset from 18 different hospitals across Beijing-Tianjin-Hebei region in China within 1 year. All the patients will undergo HR-MRI for intracranial arteries at baseline, one-year, and two-years. The clinical risk factors will be collected and blood draw will be conducted. The ICASMAP study may help to improve the precise diagnosis and intervention of ICAS and stroke prevention.

Inclusion Criteria:

• Patients with recent transient ischemic attack or ischemic stoke within two weeks after symptom onset and intracranial artery stenosis (30%-99%) at least in intracranial internal carotid artery,basilar artery, M1 segment of middle cerebral artery , A1 segment of anterior cerebral artery, or P1 segment of posterior cerebral artery determined by computed tomography angiography or magnetic resonance (MR) angiography.

Exclusion Criteria:

• Patients with specific carotid artery atherosclerotic plaques
• Patients with evidence of may causing cardiac thrombosis disease
• Patients with claustrophobia
• Patients with contraindications to MR imaging
• Patients with heart or respiratory failure
• Patients with renal insufficiency (serum creatinine >133umol/L)
• Patients with serious disturbance of consciousness
• Patients with brain tumors
• Patients with cerebral hemorrhage
• Pregnant woman or plan to pregnant within recent 2 years

In this study, we plan to recruit patients with recent transient ischemic attack or ischemic stoke within two weeks after symptom onset and intracranial artery stenosis (30%-99%) at least in intracranial internal carotid artery,basilar artery, M1 segment of middle cerebral artery, A1 segment of anterior cerebral artery, or P1 segment of posterior cerebral artery determined by computed tomography angiography or magnetic resonance angiography. The patients will be recruited from 18 hospitals in Beijing-Tianjin-Hebei area of China.