Approximately 40% of cerebral infarctions can not be classified asstrokes of determined cause despite a complete diagnostic work-up and canbe referred to as stroke of undetermined etiology. Little attention had beenpaid to atherosclerotic disease of the aortic arch as a possible source ofcerebral emboli. The prevalence of relevant plaques in the aortic arch ishigh in patients with cryptogenic stroke. Recently, aortic archatherosclerotic plaques have been implicated as a cause of cryptogenicstroke in the elderly and have been linked to an increased risk ofthromboembolic events. The aim of this study was to unmask one of thehidden pathogenic mechanism underlying cryptogenic ischemic strokethrough assessment of atherosclerotic aortic arch plaque using both TEEand MDCT angiography as a recent tool for identification of plaquethickness and morphology. This study was conducted on 30 patients withischemic stroke of undetermined etiology and 10 normal control subjects.Patients were recruited from the neurology out patient clinics of Kasr El-Aini Hospital in the period from April 2007 to August 2008, the controlswere collected randomly. Patients were subjected to clinical evaluation(history taking and examination), laboratory work up including: completeblood count and erythrocyte sedimentation rate, fasting and 2 hours postprandial blood sugar levels, lipid profile including cholesterol andtriglycerides, serum uric acid, liver and kidney functions. CT brain wasdone together with color coded duplex sonography of the extracranial andintracranial vasculature, TEE and MDCT angiography of the thoracic aorta.