leaky blood-brain barrier may lead to Alzheimer's disease

Researchers using a contrast-enhanced MRI technique have found that leakages in the blood-brain barrier (BBB) may lead to early onset of Alzheimer's disease (AD).

The BBB -- a collection of cells and subcellular structures that separates the circulating blood from the brain -- is essential to keep brain tissue in healthy condition. 

It regulates the delivery of important nutrients and blocks neurotoxins, while removing surplus substances from the brain.

"Blood-brain barrier leakage means that the brain has lost its protective means, the stability of brain cells is disrupted and the environment in which nerve cells interact becomes ill-conditioned," said Walter H. Backes from the Maastricht University Medical Center in Maastricht, the Netherlands. 

The findings showed that BBB leakage rate was significantly higher in Alzheimer's patients and the leakage was distributed throughout the cerebrum -- the largest part of the brain. 

Alzheimer's patients were found to have a significantly higher percentage of leaking brain tissue in the gray matter, including the cortex -- the brain's outer layer. 

The results suggest that increased BBB permeability may represent a key mechanism in the early stages of the Alzheimer's disease, the researchers said.

"These mechanisms could eventually lead to dysfunction in the brain," Backes said.

Further, the more impairment in BBB lead to greater decline in cognitive performance in patients.

This suggested that a compromised BBB is part of the early pathology of Alzheimer's as well as part of a cascade of events eventually leading to cognitive decline and dementia.

For the study, published online in the journal Radiology, the team used contrast-enhanced MRI technique to compare 16 early Alzheimer's patients with 17 healthy age-matched controls. 

The key advantage of detecting BBB leakage with contrast MRI technique is that it can detect early microvascular changes in Alzheimer's even in cases where no directly visible cerebrovascular abnormalities can be observed.

"For Alzheimer's research, this means that a novel tool has become available to study the contribution of blood-brain barrier impairment in the brain to disease onset and progression in early stages or pre-stages of dementia," Backes said.