The purpose of this study is to evaluate the efficacy and safety of the ticlopidine + ginko biloba compared to clopidogrel in clopidogrel resistant patients undergoing carotid artery stent placement. The investigators hypothesized that ticlopidine + ginko biloba is superior than clopidogrel in terms of post-stent ischemic lesions in these patients without serious complications.

Inclusion Criteria:

• Patients scheduled for stent implantation due to carotid stenosis
• Patients resistant to clopidogrel defined by platelet inhibition rate <20% measured by Verify Now before carotid stenting
• Patients with informed consent

Exclusion Criteria:

• Antiplatelet therapy other than aspirin, clopidogrel, or ticlopidine
• Unable to perform MRI scans
• Patients with hematologic abnormalities including neutrophil <1500/ul, platelet <100,000/uL, or AST/ALT >120 U/L
• Unsuitable for participation