This multicenter, randomized, controlled trial evaluates a combined embolic protection strategy during carotid artery stenting (CAS). Carotid artery stenosis is a major cause of stroke. While stenting is an effective treatment, the procedure itself carries a risk of dislodging plaque debris, which can travel to the brain and cause new strokes or silent brain infarctions.

Currently, a distal filter (protection device) is standardly used to catch debris. However, it may not capture all particles. This study investigates whether adding a Balloon Guide Catheter (BGC)-which temporarily stops blood flow and allows for aspiration-to the standard filter protection is more effective than using the filter alone.

Patients with symptomatic (≥50% stenosis) or asymptomatic (≥70% stenosis) carotid artery stenosis who are scheduled for stenting will be randomly assigned to one of two groups:

1. Combined Protection Group: Receiving CAS using a Balloon Guide Catheter combined with a distal filter.
2. Standard Protection Group: Receiving CAS using a distal filter alone. The primary goal is to determine if the combined approach reduces the number of new ischemic lesions detected on brain MRI within 72 hours post-procedure. The study will also assess clinical stroke events over a 90-day follow-up period.

Pre-specified subgroup analyses will be conducted based on baseline symptom status (symptomatic vs. asymptomatic carotid artery stenosis) and stent design (open-cell vs. closed-cell).

1. Occlusion or severe stenosis (70% or greater) of the intracranial segment of the ipsilateral internal carotid artery system;
2. Occlusion or severe stenosis (70% or greater) of the contralateral common carotid artery or internal carotid artery;
3. History of stenting in the head and neck vessels within 3 months;
4. Coexisting other cerebrovascular diseases, such as intracranial aneurysms greater than 5 mm or cerebrovascular malformations;
5. Onset of stroke within 7 days;
6. Large old infarctions from previous stroke that may confound the evaluation of endpoints;
7. Contraindications to magnetic resonance imaging (MRI);
8. Definite risk of cardiogenic embolism (e.g., atrial fibrillation, atrial flutter, intracardiac thrombus) or clear indications for anticoagulation therapy;
9. Absolute or relative contraindications to antiplatelet therapy;
10. Pregnant or lactating women;
11. Allergy or hypersensitivity to contrast media or stent materials (e.g., Nitinol);
12. Life expectancy less than 1 year;
13. Pre-existing neurological or psychiatric disorders (e.g., severe dementia) that would confound neurological assessments;
14. Severe renal insufficiency (eGFR less than 30 mL/min).