Check following:
1. Smoking?
2. Lipid profile: how much the LDL?
3. Medical hisotry: Hypertension, Diabetes?
4. Carotis stenosis: >50%, by carotis ultrasound, CTA or MRA of neck
4. If LDL is higher than 100 with >1 stem above, start to take statins or red yeast rice (OCT).