Background and Purpose-We investigated the frequency of cerebral microembolism detected by transcranial Doppler ultrasonography in patients with clinical evidence of retinal ischemia, including transient monocular blindness, central and branch retinal artery infarction, and ischemic oculopathy, and assessed its correlation with carotid artery stenosis. Methods-Records of 331 consecutive patients examined during a 47-month period at the Neurovascular Laboratory were reviewed. Of the original 453 intracranial arteries, 186 middle cerebral arteries (MCAs) satisfied qualifying criteria that excluded patients with cardiac embolic sources. Forty-five MCAs ipsilateral to the symptomatic eye constituted the study group. The control group consisted of 141 asymptomatic MCAs. Microembolus detection studies were performed on transcranial Doppler instruments equipped with special software, and the degree of carotid artery stenosis was measured by cerebral or MR angiography or by color duplex studies. Results-Microembolism was detected in 40.0% of study MCAs and 9.2% of controls (PϽ0.001). In the study group, microembolic signals were detected in 61.9% of MCAs tested within a week of symptom onset and 20.8% of those tested afterward (PϽ0.001). Severe (Ն70%) carotid stenosis or occlusion was more frequent in the study group (PϽ0.001). Microembolic signals were detected in 25.3% and 11.2%, respectively, of MCAs distal to carotid arteries with 70% to 100% and 0% to 69% stenosis (Pϭ0.013). Conclusions-In patients without cardiac embolic sources, cerebral microembolism is frequently present on the side of retinal ischemia, particularly during the week after onset of symptoms. It is often associated with severe stenosis or occlusion of the ipsilateral carotid artery.

Objectives: To identify the most likely mechanisms of retinal ischemia and embolism in a hospital-referred population, and to determine the frequency of recurrent vascular events during the 3-month period following initial presentation. Methods: Consecutive patients presenting to 2 tertiary medical centers and their outpatient clinics were prospectively enrolled over a 22-month period. Eligible patients presented with histories of transient or permanent monocular visual loss, or had evidence of asymptomatic retinal embolism on routine ophthalmological examination. They underwent a rapid and standardized evaluation that included imaging studies as well as blood tests, and follow-up was obtained at 1 and 3 months. Results: Seventy-seven patients were enrolled. Enrollment diagnoses consisted of amaurosis fugax (n = 32), asymptomatic retinal embolism (n = 34), and central or branch retinal artery occlusion (n = 11). Eight different presumed etiologies of retinal artery distribution embolism or hypoperfusion were identified. Extracranial internal carotid artery occlusion or more than 50% stenosis was observed in 17/77 (22.1%) cases, making it the largest etiologic subgroup. Uncommon but treatable conditions were identified in 8/77 (10.4%) patients, and an etiologic diagnosis could not be made in 35/77 (45.5%) patients. Recurrent events occurred in, respectively, 14/77 (18.2%) and 6/73 (8.2%) patients at the 1- and 3-month follow-ups. They included 2 infarcts and 2 deaths; ischemic events of the retina were more common than those involving the brain. Conclusion: Severe stenosis of the extracranial internal carotid artery is the most common identified condition associated with retinal ischemia and embolism, but a variety of other, potentially treatable, conditions can be diagnosed if appropriate and specific evaluations are conducted. The frequency of recurrent vascular ischemic events is highest during the 1st month of follow-up and decreases during the 2nd and 3rd months. Recurrences range from relatively innocuous episodes of amaurosis fugax to vascular death.

Echocardiography frequently identifies lesions of the heart or aortic arch that can act as potential sources for retinal ischemia or embolism. Further studies are needed to evaluate the prognostic and therapeutic relevance of these findings.

Purpose-To investigate differences between symptomatic and asymptomatic retinal embolism regarding the frequency and source of cerebral microemboli. Methods-Thirty-seven patients with transient monocular blindness or retinal infarction and 27 patients (29 eyes) with asymptomatic retinal embolism were prospectively enrolled. Patients underwent a transcranial Doppler study and noninvasive imaging of the cervical internal carotid arteries (ICA). The middle cerebral artery (MCA) ipsilateral to the affected eye was monitored for 30 minutes for microembolic signals (MES), which were saved and analyzed offline. Age-matched controls (nϭ15) had no history of retinal or brain ischemia, Ͻ50% ICA stenosis, and normal ophthalmologic examinations. Results-MES were detected in 0/15 (0%) controls, 11/37 (30%) MCAs in the symptomatic group (Pϭ0.02), and 3/29 (10%) MCAs in the asymptomatic group (Pϭ0.54). Nine of 11 (82%) symptomatic eyes with MES had ipsilateral ICA stenosis of Ն50%, as compared with 0/3 (0%) eyes in the asymptomatic group with MES (Pϭ0.03). Both MES and ICA stenosis of Ͼ50% were present in 9/37 (24%) cases in the symptomatic and in 0/29 (0%) cases of the asymptomatic group (Pϭ0.0036). Conclusions-The

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