The purpose of CARE-HBOT study is to evaluate whether patients with symptomatic severe carotid artery stenosis with cognitive impairment who underwent hyperbaric oxygen therapy plus standard medical treatment after stent implantation could improve their cognitive function compared with those who underwent standard postoperative medical treatment.

This study is a prospective, multi-center, 1:1 randomized trial. In patients with symptomatic severe carotid artery stenosis with cognitive impairment underwent stent implantation, whether hyperbaric oxygen therapy plus standard medical treatment after stenting could improve their cognitive function compared with those who underwent standard postoperative medical treatment will be studied.

Primary endpoint: Cognitive level at 6 months of follow up.

Inclusion Criteria:

1. Age from 18 to 75 years
2. National Institute of Health stroke scale (NIHSS) ≤3
3. Culprit vessel was the common carotid artery or extracranial internal carotid artery, involving or not involving the external carotid artery
4. The degree of culprit arterial stenosis is 70-99 % ; based on Digital subtraction angiography (DSA) (According to North American Symptomatic Carotid Endarterectomy Trial (NASCET) method)
5. The diameter of the target vessel between 4.0 mm - 9.0 mm
6. Mini-mental State Examination (MMSE) score : education level-middle school ≤ 24; education level-high school ≤ 20 ; education level-college ≤ 17
7. Baseline modified Rankin Scale (mRS) score ≤ 3
8. Patient understands the purpose and requirements of the study, and has provided informed consent

Exclusion Criteria:

1. Tandem extracranial or intracranial stenosis (70%-99%) or occlusion that is proximal or distal to the target intracranial lesion
2. Serious perioperative complications affecting subsequent hyperbaric oxygen therapy (such as cerebral hemorrhage, disabling stroke, etc.)
3. Any history of brain parenchymal or subarachnoid, subdural or extradural haemorrhage in the past 12 months
4. Hemorrhagic transformation after ischemic stroke within 60 days before enrollment
5. Intracranial artery stenosis caused by non-atherosclerotic lesions, including: arterial dissection, Moyamoya disease, vasculitis disease, herpes zoster, varicella-zoster or other viral vascular diseases, neurosyphilis, any other intracranial infections, any intracranial stenosis related to cerebrospinal fluid cells, radiation-induced vascular disease, fibromuscular dysplasia, sickle cell disease, neurofibromatosis, central nervous system benign vascular disease, postpartum vascular disease, suspected vasospasm, suspicious embolism recanalization, etc
6. Nervous system diseases in the past two years, characterized by transient or fixed neurological deficits (such as partial or secondary generalized seizures of epilepsy, complex or classic migraine, tumor or other intracranial space-occupying lesions, subdural hematoma, brain contusion or other post-traumatic lesions, intracranial infection, demyelinating diseases, intracranial hemorrhage, etc.), which cannot be distinguished from cerebral infarction
7. History of stenting of an intracranial or extracranial artery
8. Presence of any unequivocal cardiac source of embolism
9. Chronic atrial fibrillation; paroxysmal atrial fibrillation or paroxysmal atrial fibrillation in the past 6 months, or a history of paroxysmal atrial fibrillation, requiring long-term anticoagulation
10. Myocardial infarction in the past 30 days
11. Combined with intracranial tumor, aneurysm or intracranial arteriovenous malformation
12. Cannot tolerate dual antiplatelet therapy due to known diseases (such as gastrointestinal bleeding)
13. Contraindications to heparin, aspirin, clopidogrel, ticagrelor, anesthesia, or contrast agents
14. Hemoglobin<100g/L, platelet count <100×109/L, international normalized ratio (INR)>1.5, or heparin-related thrombocytopenia or uncorrectable factors leading to bleeding
15. Not suitable for vessel angiography or endovascular interventional therapy (such as morbid obesity; serious vascular tortuosity that hinders the safe introduction of the guiding catheter)
16. Severe hepatic and renal dysfunction
17. Major surgery within the past 30 days or planned within 90 days
18. Renal artery, iliac artery, and coronary artery requiring simultaneous intervention
19. Life expectancy <1 year
20. Pregnant or lactating women
21. Cognitive assessment and follow-up could not be completed due to factors such as severe aphasia, neuropsychological illness or mental illness or dysarthria and inability to communicate
22. History of drug or alcohol abuse, head trauma or central nervous system infection; current use of drugs that affect cognition
23. Combined with diseases that are not suitable for hyperbaric oxygen therapy (such as untreated pneumothorax, uncontrolled epilepsy, claustrophobia, angle-closure glaucoma, cavitary pulmonary tuberculosis, etc.)
24. Enrollment in another study that would conflict with the current study