Explainer : Reason for placement of lesions in brain

The reason for the placement of lesions in the brain as well as how they develop in the first place was recently explained by a study led by Stevens Institute of Technology researchers.

The study has been published in the 'Scientific Reports Journal'.

The work, led by Johannes Weickenmeier, an assistant professor of mechanical engineering at Stevens Institute of Technology, highlighted the importance of viewing the brain as more than neural circuitry that underpinned how thoughts are formed, and memories created. It's also a physical object that's prone to glitches and mechanical failures.

"The brain is susceptible to wear and tear in vulnerable areas. Especially in an ageing brain, we need to look at its biomechanical properties to better understand how things can start to go wrong," Weickenmeier said.

These lesions -- known as deep and periventricular white matter hyperintensities because they show up as bright white patches on MRI scans -- are poorly understood. But they are not uncommon: most people have some by the time they reach their 60s, and changes only increase with age.

The more lesions that accumulate and the faster they grow, the more prone we become to cognitive impairments ranging from memory problems to motor disorders.

Using MRI scans from eight healthy subjects, W`eickenmeier worked with Valery Visser, now a doctorate student at the University of Zurich, and Henry Rusinek, a radiologist at NYU Grossman School of Medicine, to develop an individualized computer model of each subject's brain. The team mapped the strain placed on ventricular walls, the linings of fluid-filled chambers deep in the brain, as waves of pressure pulse through the subject's cerebral spinal fluid, or CSF.

They found that hyperintensities tended to occur near areas that must stretch more to accommodate pressure changes of the circulating CSF because, as such areas wear thin, CSF can leak into the brain and cause lesions.

"The cell wall that lines the ventricles wears out over time, like a balloon that's repeatedly blown up and deflated. And the stresses aren't uniform -- they're defined by the geometry of the ventricle, so we can predict where these failures will occur," Weickenmeier said.

"The model provides a simple, physics-based explanation for the locations of these lesions, revealing that mechanical loads must be a major contributor to the onset of disease," added Weickenmeier.

The team's research used 2D imaging showing a cross-section of the brain, but Weickenmeier's team has since expanded its research to a full 3D model of the brain. Next, Weickenmeier hopes to use advanced MRI technologies developed at Stevens to study the movement of the ventricle wall directly.

In the long term, the team's findings might enable the development of new treatments for lesions. Ordinarily, pharmaceutical treatments struggle to cross the blood-brain barrier and reach affected areas, but the new research suggested that it might be possible to channel drugs to lesions directly through leaks in the ventricular wall.

"That's still a long way off, and we didn't study it directly. But it's an intriguing possibility," Weickenmeier cautioned.

The broader takeaway from the team's research, explained by Weickenmeier, is that the brain's ageing process is mediated by physical processes, including the pressure of circulating blood and CSF. That underscores the need for healthy behaviours -- such as getting enough exercise and avoiding harmful substances -- that can reduce those strains on the brain.