Detection of intracranial emboli in patients with carotid disease

Transcranial Doppler emboli signal detection has been reported in several patient groups, including patients with symptomatic internal carotid artery stenosis. The potential of this technique in assessing embolic risk and selecting patients for surgery was examined in this study. Selected patients with symptomatic internal carotid artery stenosis underwent combined extracranial and transcranial Doppler study in the Vascular Surgery and Neurovascular Unit. Patients and normal controls were monitored with transeranial Doppler over both middle cerebral arteries. Severity of carotid disease was diagnosed with colour Duplex ultrasound examination or angiography. Selected patients underwent cranial computed tomography and transthoracic echocardiography. Patients undergoing carotid endarterectomy were re-examined one month after surgery. Fifty symptomatic patients, six asymptomatic patients and 30 normal controls were examined. Carotid disease was unilateral in 34 and bilateral in 22 cases. Emboli signals were detected in 94% of patients. The emboli signal count in patients with unilateral carotid stenosis was significantly higher in the middle cerebral artery distal to the stenosed internal carotid compared to the contralateral middle cerebral artery 114 (10–22) versus 2 (0–7) signals per hour, median and 95% confidence intervals, p < 0.0011 and in symptomatic compared to asymptomatic cerebal hemispheres 115 (11–21) versus 4 (2–9) signals per hour, p < 0.0011. Emboli were detected in the contralateral middle cerebral artery in 40% of patients with unilateral carotid disease, in 85% of whom an additional embolic source was identified. No emboli signals were detected after carotid endarterectomy distal to the operated internal carotid, or in any of the normal controls. In conclusion, intracranial emboli signals are common in patients with carotid stenosis. Carotid endarterectomy eliminates emboli signals distal to the operated internal carotid. The clinical significance of these signals remains to be determined by prospective studies.