The Prevalence of Asymptomatic Intracranial Large-Vessel Occlusive Disease: The Role of Diabetes

OBJECTIVE: To investigate the prevalence of asymptomatic intracranial stenosis using transcranial Doppler ultrasonography in patients with evidence of asymptomatic carotid stenosis. BACKGROUND: Symptomatic atherosclerotic intracranial largeartery stenosis accounts for approximately 10% of ischemic strokes annually. It is unknown whether a significant risk for stroke is associated with asymptomatic intracranial stenosis, especially in patients with known asymptomatic carotid disease. DESIGN AND METHODS: Transcutaneous real-time B-mode Doppler ultrasonography was performed on 510 patients referred for the evaluation of asymptomatic carotid bruits. A peak systolic flow velocity > 1.40 m/s indicated carotid stenosis. Transcranial Doppler ultrasound was performed to identify intracranial large-artery disease. The peak systolic flow velocity indicating stenosis was > 120 cm/s for anterior circulation and > 100 cm/s for posterior circulation. Demographic and cerebrovascular risk factor information was recorded at the time of examination. Chi-square analysis with Pearson correction was performed to examine the significance of the findings. RESULTS: Five hundred ten patients (252 male, 258 female) aged 71.4 +/- 10.45 years were studied. The laboratory's accuracy was previously established as 93% for each technique for laboratory certification. Two hundred patients (39.2%) were found to have extracranial carotid stenosis, and 66 (12.9%) were found to have intracranial stenosis. Thirty-seven patients (56%, P < .01) were found to have concurrent stenosis. In patients with intracranial stenosis, 19 (28.8%, P < .03) had diabetes, and 26 (39.4%, p < .03) had coronary disease. There was no corresponding correlation with extracranial carotid disease and diabetes or coronary artery disease. CONCLUSIONS: The prevalence of patients with asymptomatic intracranial stenosis with concurrent carotid stenosis was greater than expected. Coexisting diabetes and coronary disease were significant risk factors in this population. Doppler ultrasonography may be a useful technique in delineating asymptomatic intracranial stenosis in those patients with existing carotid stenosis. Further studies are needed to clarify the risk of this population for stroke from asymptomatic intracranial stenosis and to determine optimal therapy.