Cerebral microbleeds and dementia: Number and location matter

Building on prior research establishing the prevalence of cerebral microbleeds in Alzheimer’s patients, investigators in the Netherlands have used MRI in a large, longitudinal study to show that the related extent of cognitive decline and dementia depends on how many bleeds the patient has and where they’re located within the brain.

The study report posted online June 6 in JAMA Neurology.

Saloua Akoudad, MD, PhD, of University Medical Center Rotterdam and colleagues recorded the completion of baseline and follow-up testing on 3,257 participants (mean age, 59.6) during the period from 2002 to 2014.

The patients, all members of the prospective, population-based Rotterdam Study, underwent neuropsychological assessment at baseline and at a mean of 5.9 years later.

The testing also incorporated 1.5-T MRI of the brain, which included T2-weighted sequences for detection of cerebral microbleeds.

Cerebral microbleeds were found in 15.3 percent of the cohort, and the research team’s key findings included:

• The presence of more than four cerebral microbleeds was associated with cognitive decline.
• Microbleeds in any number were associated with an increased risk for dementia—including Alzheimer dementia—after adjustment for age, sex and educational level.
• After a mean follow-up of 4.8 years, 72 participants developed dementia; of these, 53 (36 percent) had Alzheimer dementia.
• Lobar microbleeds were associated with a decline in executive function, information processing and memory.
• Microbleeds in other regions of the brain correlated with a decline in information processing and motor speed.

While the results did not make clear whether or not the cerebral microbleeds caused the cognitive decline, the authors stress in their discussion that these microbleeds “are associated with cognitive decline and dementia in the general population. Microbleeds thus mark the presence of diffuse vascular and neurodegenerative brain damage.”

In accompanying commentary, Philip Gorelick, MD, PhD, of Michigan State University and Muhammad Farooq, MD, of Mercy Health Hauenstein Neuroscience Center in Grand Rapids, Mich., point out that MRI-detected cerebral microbleeds are common in elderly individuals, coexist with ischemic stroke and intracerebral hemorrhage of various types, and are associated with several cardiovascular risks.

As for the clinical implications of the body of research on which the Akoudad et al. study builds, Gorelick and Farooq write that, because these bleeds may have a role in determining cognitive outcome, and because of their relationship with intracerebral hemorrhage, “their presence challenges physicians to make decisions regarding administration of antithrombotics, acute thrombolytics and other cardiovascular therapies that may lead to brain hemorrhage.”

“Because no high-level evidence-based or definitive studies are available to guide one in the administration of antithrombotics for first or recurrent stroke prevention or thrombolysis in acute ischemic stroke,” Gorelick and Farooq conclude, “physicians must adopt a practical approach when administering these medications to patients with cerebral microbleeds.”