**15. Carotid diseases, stroke, and cholesterol**

Ischemic stroke should be investigated in two groups as embolic and thrombotic stroke.

Smoking and age are the most important risk factors for carotid atherosclerosis. The atherosclerotic plaque is located in the bifurcation area and often extends on the outer wall of the carotid bulb.

When stenotic plague increases, the risk of emboli increases. Carotid stenosis is defined as a stenosis of 50% or more in the extracranial portion of the internal carotid artery. In addition to the luminal narrowing, the lesion's edge irregularity, the presence of intraplate plaque hemorrhage, whether the lesion is unilateral or not, also determines the severity of the disease. Symptomatic carotid stenosis is the occurrence of symptoms related to carotid stenosis in the last 6 months.

In the heart protection study with simvastatin, a reduction of 39 mg/dL at the LDL level resulted in a 20% reduction in major cardiovascular events, 25% reduction in stroke, and 38% reduction in ischemic stroke [11].

In the SPARCLE trial (stroke prevention by aggressive reduction in cholesterol levels), patients who had stroke and TIA within the last 1–6 months were evaluated for 5 years. In patients receiving high-dose atorvastatin, a reduction of 43% in LDL levels resulted in a 20% reduction in major cardiovascular events and a 16% reduction in stroke. Despite the increase in hemorrhagic stroke rates in the high-dose statin group, there was no difference in lethal hemorrhagic stroke [27, 28].

It has been suggested that statin therapy initiated after stroke also improves neurological function with a decrease in infarct area. According to the information obtained from the metaanalyses, the use of statin before and after stroke is associated with improvement in neurological function. However, there was a relationship between statin therapy and hemorrhagic transformation in cases treated with thrombolytic therapy [29].

Carotid intima media thickness is a subclinical atherosclerosis indicator and it is recommended to use it in addition to classical cardiovascular risk indicators, especially in individuals with hypertensive middle cardiovascular risk (SCORE risk 1–5%). Values above 0.9 mm or values above normal 75th percentile should be considered pathological. According to the American Society of Echocardiography, these individuals should be considered as having increased CV risk. Individuals between 75 and 25% have expected cardiovascular risk. Individuals below the 25th percentile have low cardiovascular risk [30].
