• Symptomatic ICAS. Participants with ICAS with a transient ischaemic attack (TIA) or stroke attributable to the territory of the stenotic artery were defined as symptomatic. A TIA was defined as a transient episode of neurological dysfunction (focal weakness or language disturbance, transient monocular blindness, or required assistance in walking) caused by focal brain or retinal ischaemia that lasted for at least 10 minutes but resolved within 24 hours

• Stenotic degree ≥ 50%, measured by digital subtraction angiography

• The stenosis must located in at least one major intracranial artery (internal carotid artery, vertebral artery, middle cerebral artery, or basilar artery)