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Silent cerebral infarctions - parenchymal lesions detected on MRI in the absence of stroke symptomatology - may be present in early middle age and are associated with many of the same risk factors as clinical stroke, according to findings from a community-based cohort study.

Dr. Sudha Seshadri, at Boston University School of Medicine, and associates determined the prevalence of silent cerebral infarctions (SCI) in the Framingham Offspring Study. The cohort included 2040 subjects, mean age 62 years, free of stroke and cognitive impairment when they underwent brain MRI between 1998 and 2001.

The overall prevalence of SCI was 10.7 per cent, increasing from about seven per cent in subjects aged 30-49 years to > 15 per cent in subjects ages 70-89, the authors report in the November issue of Stroke, posted early online on June 26.

They observed that 52 per cent of infarcts were located in the basal ganglia, 35 per cent in the subcortex, 11 per cent in the cortex, two per cent in the cerebellum, and 0.5 per cent in the brainstem.

"It has been speculated that SCIs are silent (or rather produce subtle neurological damage) because they occur in clinically ineloquent areas of the brain," the investigators note. "The predominance of lesions in the basal ganglia and their being found subcortically rather than cortically appear to support this hypothesis."

SCI was significantly associated with Framingham Stroke Risk Profile score (OR 1.27 per 1 SD increase), hypertension (OR 1.56), elevated plasma homocysteine level in the highest quartile (OR 2.23), atrial fibrillation (OR 2.16), carotid stenosis > 25 per cent (OR 1.62), and increased carotid intimal-medial thickness above the lowest quintile (OR 1.65).

These findings reinforce the importance of prevention, early detection and treatment of cardiovascular risk factors in mid-life, Dr. Seshadri's group maintains. "This is especially true because SCI has been associated with an increased risk of incident stroke and cognitive impairment."

However, they note, since subjects of the study were primarily of European descent, the findings may not be generalizable to other ethnic groups.