Subclinical Infarcts on MRI Linked to Functional Decline

Nancy A. Melville

October 01, 2015

CHICAGO — Subclinical brain infarcts and white matter hyperintensities on MRI of stroke-free patients are associated with double the rate of functional decline, a new study shows.

"We suspected that subclinical brain injury is responsible for a great deal of disability, but the degree of additional decline in the presence of subclinical brain injury was surprising: there was approximately a doubling of the degree of decline over time," first author Mandip S. Dhamoon, MD, MPH, an assistant professor of neurology at the Icahn School of Medicine at Mount Sinai, in New York, New York, told Medscape Medical News.

Their findings were presented here at the American Neurological Association (ANA) 2015 Annual Meeting.

The study involved 1290 patients in the Northern Manhattan Study who had undergone brain MRI but had not experienced strokes. A median of 11 years of annual functional assessments were available for the patients, obtained by using the Barthel index (range, 0 to 100). The index measures factors such as feeding, bathing, bowel and bladder control, ambulation, and stair climbing. The patients also had vascular event surveillance.

They had a mean age of 70.6 years, 40% were male, and 66% were Hispanic.

Among the patients, 193 (16%) showed subclinical brain infarcts on MRI, and their mean white matter hyperintensity volume (percentage of total cranial volume) was 0.68.

During the 11-year follow-up, the overall functional change was a reduction of 0.85 points on the Barthel index per year (95% confidence interval [CI], –1.01 to –0.69). Among those with subclinical brain infarcts, there was an additional reduction of 0.88 points annually (95% CI, –1.44 to –0.32).

The functional change observed with white matter hyperintensity was a reduction of 1.04 points (95% CI, –1.2 to –0.88) annually, with an additional reduction of 0.74 points annually per SD of white matter hyperintensity increase (95% CI, –0.99 to –0.49).

Dr Dhamoon and his colleagues additionally found in a study published last year in the Annals of Epidemiology that key vascular risk factors for functional decline include diabetes, as well as age, female sex, and depression.

"Future research will clarify this, but it seems reasonable that treatments can be implemented that not only reduce the risk of clinical events, but also reduce functional decline due to subclinical ischemic brain disease," he said.

Small cerebral lesions of less than 3 mm are often dismissed as being inconsequential, but another recent study also showed important implications. In that study, published in the Annals of Internal Medicine in June, researchers found that the presence of cerebral lesions smaller than 3 mm conferred a stroke risk more than triple that of having no lesions (hazard ratio [HR], 3.47), while the risk doubled with lesions 3 mm or larger (HR, 1.94) and was as much as 8-fold higher when both sizes were present (HR, 8.59).

"Very small cerebrovascular lesions may be associated with increased risks for stroke and death; presence of lesions smaller than 3 mm and 3 mm or larger may result in a particularly striking risk increase," the authors concluded.

According to stroke specialist Lesli E. Skolarus, MD, MS, an assistant professor with the Neurology Stroke Program at the University of Michigan, in Ann Arbor, Michigan, the latest study adds to the improved understanding of the role of stroke and function.

"Given the aging baby boomer population, optimizing stroke survivorship is increasingly important. Studies, such as this, that identify associations of imaging characteristics with functional decline are important steps toward improving stroke survivorship," she told Medscape Medical News.

The study was supported by a grant from the National Institute of Neurologic Disorders and Stroke.

American Neurological Association (ANA) 2015 Annual Meeting. Abstract M307. Presented September 28, 2015.

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