Estimated prevalence of acoustic cranial windows and intracranial stenosis in the US elderly population: ultrasound screening in adults for intracranial disease study.

Background: Intracranial atherosclerosis is an important etiology of stroke in the USA, but its prevalence in the general population remains unknown. This study was performed to determine the feasibility of transcranial Doppler ultrasound (TCD) for general population screening and to estimate the prevalence of intracranial stenosis in the USA.

Methods: We used a public database to randomly select 99 subjects aged 65-84 years residing in a well-defined geographic area. For all subjects clinical history was reviewed, blood pressure was recorded and TCD examination was performed to identify intracranial stenosis.

Results: The mean age of subjects was 72 years, 42 were men, and 17 were African-Americans. All acoustic windows were present in 77 subjects. After multivariate adjustment, the odds of absence of a bone window were higher in African-Americans [odds ratio (OR) 6.0, 95% confidence interval (CI) 1.8-2.0], nonsmokers (OR 3.1, 95% CI 1.0-9) and those with a high BMI (9% higher odds per index point). Among 77 subjects who had all acoustic windows present, intracranial stenosis of >50% was identified in 6.5%, and intracranial stenosis of any severity was identified in 16% of the persons. Intracranial stenosis was most prevalent in the middle cerebral artery (6%).

Conclusion: Presence of acoustic windows is associated with vascular risk factors. Based on the high prevalence of significant intracranial stenosis in the US elderly population, it is feasible and important to perform a large-scale population-based study for this disease entity.