Microbleeds More Common Than Previously Thought

Caroline Cassels

April 01, 2008

April 1, 2008 — The most recent results from the Rotterdam Study show cerebral microbleeds are more common in individuals over age 60 years than previously thought.

The study found the overall prevalence of cerebral microbleeds in healthy elderly subjects was 17.8% in individuals aged 60 to 69 years and 38.3% in those over age 80 years.

"We found a 3- to 4-fold higher overall prevalence of cerebral microbleeds compared with other population-based studies," principal investigator Monique Breteler, MD, PhD, from Erasmus MC University Medical Center, in Rotterdam, the Netherlands, said in a statement from the American Academy of Neurology.

"These findings are of major importance, since cerebral microbleeds likely reflect cerebrovascular pathology and may be associated with an increased risk of cerebrovascular problems," she added.

The study is published in the April 1 issue of Neurology.

Optimized MRI

Established in 1990, the Rotterdam Study is a prospective, population-based study aimed at assessing diseases in the elderly and clarifying their determinants.

According to the paper, little is known about the exact etiology of microbleeds in the general population. They often accompany intracerebral hemorrhage (ICH). It has also been suggested that the etiology of microbleeds differs according to location in the brain, with lobar microbleeds caused by cerebral amyloid angiopathy (CAA) and deep, or infratentorial, microbleeds resulting from hypertension and atherosclerosis.

To investigate the prevalence of and risk factors for microbleeds in the general population aged 60 years and older, the investigators performed brain magnetic resonance imaging (MRI) in 1062 healthy subjects. Of note, the MRI sequence was optimized for the detection of cerebral microbleeds.

In addition, investigators assessed the relationship of APOE genotype, cardiovascular risk factors, and markers of small-vessel disease to the presence and location of microbleeds.

Risk Factors Determine Location

The investigators speculate that 1 possible explanation for the higher prevalence of microbleeds in their study vs previous research may be due to the fact that Rotterdam Study population is older and their "custom-made" imaging technique has a higher sensitivity in detecting cerebral microbleeds.

In addition to a high prevalence of microbleeds, the study also showed that there was a strong link with the APOE ε4 allele and the presence of lobar microbleeds.

"As in Alzheimer disease, the APOE ε4 allele is a known risk factor for lobar ICH and CAA. . . . Although the exact molecular mechanism is not clear, APOE ε4 carriership is presumed to lead to hemorrhage by increased vascular deposition of β-amyloid," the authors write.

However, the APOE ε4 genotype was not associated with deep or infratentorial microbleeds. Instead they found high systolic blood pressure and smoking were associated with lesions in this region.

"The high prevalence of cerebral microbleeds in our study as well as the finding that risk factors vary according to microbleed location has major importance in view of previous reports from small clinical series suggesting that microbleeds may reflect an increased risk of recurrence of stroke and hemorrhagic transformation of ischemic stroke," the authors write.

The study was supported by the Erasmus MC University Medical Center and Erasmus University Rotterdam, the Netherlands Organization for Scientific Research, and the Netherlands Organization for Health Research and Development.

Neurology. 2008;70:208-1214.

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