BackgroundStroke is the third leading cause of death in developed nations. Ultrasonography (US) of the carotid arteries is the modality of choice for diagnosis and monitoring of cases of atheromatous disease. Cystatin C (CysC) is a risk factor for cerebrovascular and cardiovascular disease.ObjectivesTo detect the association of serum CysC levels with acute ischemic stroke, the correlation of its levels with stroke severity, and the association between CysC levels with extra- and intracranial stenosis.MethodsCase-control study was conducted on 66 subjects, 33 patients within the first week of stroke onset with age range from 40 to 75 years, and 33 control healthy subjects with matched age and sex. All subjects underwent complete neurological examination, Extra- and transcranial duplex, CT brain, routine laboratory work-up, and serum CysC.ResultsSerum CysC levels were significantly raised in patients with acute ischemic stroke compared to controls. CysC levels were higher in patients with extracranial stenosis than in those with intracranial stenosis. Moreover, extracranial stenosis > 50% has higher levels of CysC. Serum CysC level showed a significant correlation with National Institutes of Health Stroke Scale (NIHSS) and intima-media thickness (IMT).ConclusionSerum CysC can be used as a marker for acute atherosclerotic ischemic stroke and stroke severity. High-grade extracranial stenosis has the highest level of CysC.