Silent infarcts and cerebral microbleeds modify the associations of white matter lesions with gait and postural stability: population-based study.

BACKGROUND AND PURPOSE: Although cerebral white matter lesions (WMLs), silent infarcts (SIs), and microbleeds (MBs) are individually associated with poorer gait and balance, it is unknown if they interact. We studied the interactions of WML volume with SI and MB on gait and postural stability. METHODS: Participants in a population-based study aged 60 to 86 years underwent brain MRI, computerized gait measurement, and a physiological profile assessment of postural stability. Segmentation procedures and standard rating methods were used to measure WML, SI, and MB. Linear regression was used to test interactions between lesions on gait and postural stability, adjusting for age, sex, and total intracranial volume. RESULTS: There were 395 participants (mean age, 72 years; SD, 7.0). SIs were predominantly located in subcortical frontal white matter and in deep gray structures, and MBs were largely lobar. Participants with SI or MB had higher WML volumes than those without (P<0.001 and P=0.05, respectively). The presence of SI (P for interaction=0.01) or MB (P for interaction <0.01) magnified the adverse association of WML volume with gait. SI (P for interaction=0.02), but not MB, magnified the adverse association of WML volume with postural stability. CONCLUSIONS: Subclinical cerebrovascular lesions are adversely associated with gait and postural stability in older people in a cumulative fashion.

Carotid artery anatomy and geometry as risk factors for carotid atherosclerotic disease.

BACKGROUND AND PURPOSE: Traditional vascular risk factors do not completely explain the asymmetry, racial, and sex differences in carotid artery disease. Carotid anatomy and geometry may play a role in the pathogenesis of internal carotid artery (ICA) stenosis, but their effects are unknown. We hypothesized that carotid artery anatomy and geometry would be independently associated with ICA stenosis. METHOD: This is a retrospective study of patients with CT angiography at Monash Medical Centre, 2006 to 2007. Carotid arteries were segmented using semiautomated methods to estimate measures of carotid anatomy and geometry. Measurements of carotid artery geometry were performed according to the recent article by Thomas and colleagues. ICA stenosis was dichotomized as <30% or ≥ 30% stenosis. Cluster logistic regression was used to examine the associations of anatomy and geometry with stenosis accounting for the paired arteries within subjects, adjusting for age, sex, and vascular risk factors. RESULTS: Mean age of the sample (n=178) was 68.4 years (SD, 14 years). The following were independently associated with ICA stenosis: ICA radius at the bifurcation (OR, 0.20; 95% CI, 0.14-0.29), ICA angle (OR, 1.05 per degree increment; 95% CI, 1.04-1.07), age (OR, 1.05 per year increment; 95% CI, 1.03-1.07), male sex (OR, 1.72; 95% CI, 1.08-2.8), and ever-smoker (OR, 1.85; 95% CI, 1.15-2.96). CONCLUSIONS: Carotid anatomy and geometry may enhance the risk of stenosis independent of traditional vascular risk factors and may be of help in very early identification of patients at high risk of developing carotid artery atherosclerosis for aggressive intervention.

Does the principle of minimum work apply at the carotid bifurcation: a retrospective cohort study.

BACKGROUND: There is recent interest in the role of carotid bifurcation anatomy, geometry and hemodynamic factors in the pathogenesis of carotid artery atherosclerosis. Certain anatomical and geometric configurations at the carotid bifurcation have been linked to disturbed flow. It has been proposed that vascular dimensions are selected to minimize energy required to maintain blood flow, and that this occurs when an exponent of 3 relates the radii of parent and daughter arteries. We evaluate whether the dimensions of bifurcation of the extracranial carotid artery follow this principle of minimum work. METHODS: This study involved subjects who had computed tomographic angiography (CTA) at our institution between 2006 and 2007. Radii of the common, internal and external carotid arteries were determined. The exponent was determined for individual bifurcations using numerical methods and for the sample using nonlinear regression. RESULTS: Mean age for 45 participants was 56.9 ± 16.5 years with 26 males. Prevalence of vascular risk factors was: hypertension--48%, smoking--23%, diabetes--16.7%, hyperlipidemia--51%, ischemic heart disease--18.7%.The value of the exponent ranged from 1.3 to 1.6, depending on estimation methodology. CONCLUSIONS: The principle of minimum work (defined by an exponent of 3) may not apply at the carotid bifurcation. Additional factors may play a role in the relationship between the radii of the parent and daughter vessels.