Cerebral hemodynamic compromise from internal carotid artery stenosis may be a cause of vascular cognitive impairment that is amenable to treatment by revascularization. The effect of carotid artery stent on evoked cerebral blood oxygenation and neurocognitive functioning will be evaluated by functional near-infrared spectroscopy. Carotid artery stent could benefit cerebral blood oxygenation after stent and improving neurocognitive functioning after 6 months.

Patients with high grade internal carotid artery stenosis intended to carotid artery stent are brought to this study. Global cognitive function and evoked cerebral blood oxygenation are evaluated before and after stent, followed up at 6 months later. Mini-Mental State Examination(MMSE) and Montreal Cognitive Assessment (MoCA) are used for the global cognitive test. Evoked cerebral blood oxygenation is evaluated using functional near-infrared spectroscopy(fNIRS) through performing mental task( N-back task, Go/no go task, and verbal fluency task ). All the patients from different centers are conducted the test at the only main center by one doctor. The parameter of fNIRS and score of cognitive test of each patient are compared before and after stent.

Inclusion Criteria:

1. 35-80 years old
2. Severe carotid stenosis (MRA or CTA confirmed stenosis rate of 70% - 99%, NASCET standard)
3. Asymptomatic or mild stroke (NIHSS ≤ 3) or TIA
4. Agree to participate in the clinical trial and sign the informed consent

Exclusion Criteria:

1. Severe stenosis or occlusion of vertebrobasilar artery and other intracranial arteries (70% - 99%)
2. Left ventricular ejection fraction < 50% or heart failure
3. Other types of dementia have been diagnosed
4. Severe depression, mental illness, epilepsy
5. Not cooperating with cognitive task evaluation

Patients with high grade carotid artery stenosis treated with carotid artery stent from 5 hospitals.