Up to 70 percent of people living with Multiple Sclerosis (MS) experience cognitive impairment as a result of the disease. This can range from difficulty with memory recall to taking a long time to complete tasks, all of which have a big impact on a person’s day-to-day life. While it’s been known for a long time that cognition can be impaired in MS, the reason behind this particular symptom has remained largely unclear.
New research from DMCBH researcher Dr. Shannon Kolind’s lab has found some answers. The team used a technique called myelin water imaging and discovered that more myelin damage correlated with lower cognitive scores.
“Myelin water imaging was pioneered at UBC in the 90’s, but no one has used it to look at its relationship to cognitive symptoms in MS with tests that are validated for use in the disease,” explains Shawna Abel, PhD candidate in the Kolind lab and lead author of the study.
Myelin—which is attacked and damaged by a person’s own immune system when they have MS—acts as an insulating layer that protects nerve fibers in the brain and spinal cord. Myelin water imaging is a technique designed by physicists that acts as a biomarker for myelin. By detecting the MRI signal that comes from different biological tissue in the brain (e.g., myelin water vs intra- and extracellular water), researchers are able to determine which signals are specific to myelin and can therefore quantify how much myelin is actually in the brain or spinal cord at any given time.
Abel and her team ran this imaging technique on people diagnosed with MS as well as healthy controls. Both sets of participants then underwent a series of cognitive tests.
“By doing this, we were able to get a myelin water fraction value from the person’s brain and a cognition score from their tests and then we looked at the relationship between these two factors,” says Abel. “What we found is a correlation between myelin and cognitive scores in people living with MS, but this same relationship doesn’t exist in healthy controls. In other words, people with more myelin damage had lower cognitive scores.”
This is one of the first studies to show that myelin might be playing a role in cognitive impairment in MS, which is important in terms of drug development. Many of the MS drugs in the pipeline for pharmaceutical use are targeted at repairing myelin. This means knowing how myelin damage is involved in cognitive impairment will be essential in order to target and test the use of these treatments in slowing down the rate of declining cognition.
The team is now looking to follow this cohort over the next several years and continue to measure myelin water fraction as well as cognitive scores to see how they change over time.
“The idea is that we’ll be able to look and see if scans and test scores from two years ago are predictive of how someone is doing four years later,” says Abel. “We now have a specific biomarker for myelin so if we test these new drugs in a trial, we can take the myelin scan and cognitive scores and see if people are increasing or decreasing in myelin from baseline and how this relates to an improvement or worsening in their cognitive symptoms.”