Patients with PIRA have more damage to white matter: Study
More severe disability, greater lesion load found than in patients without PIRA
People with multiple sclerosis (MS) who experience progression independent of relapse activity (PIRA) tend to have greater damage to major white matter tracts, or bundles of nerve fibers that connect different regions of the brain, a new study reports.
The findings offer some insights into the biological processes that may contribute to PIRA, a less understood form of MS progression that occurs in the absence of relapses.
The study, “White Matter Tract Degeneration in Multiple Sclerosis Patients With Progression Independent of Relapse Activity,” was published in Neurology Neuroimmunology & Neuroinflammation.
MS is marked by inflammation in the brain and spinal cord that causes damage to the myelin sheath, a fatty coating around nerve fibers that helps electrical signals travel more efficiently. Damage to myelin disrupts communication between nerve cells and leads to MS symptoms.
White matter contains wire-like projections used by nerve cells to communicate
Within the brain, there are two main types of tissue: gray matter, which contains the bodies of nerve cells, and white matter, which contains the long, wire-like projections that nerve cells use to communicate. White matter gets its name due to its high myelin content, which has a white color.
Most people with MS experience relapses, or sudden flare-ups of symptoms, followed by remissions, where those symptoms ease or go away entirely. When a person doesn’t recover fully from a relapse and some symptoms are retained, this can drive long-term disability.
However, patients can also experience disability progression in the absence of relapses, which is a form of progression known as PIRA. The changes in the brain that drive PIRA, however, are not fully understood.
A team led by scientists in Switzerland set out to determine whether there is a connection between damage to myelin-rich white matter and PIRA among people with MS.
The team examined data from 258 people with relapsing-remitting MS who were followed between 2016 and 2022 as part of the Swiss Multiple Sclerosis Cohort study.
Patients with at least 1 PIRA event had more severe disability
Of them, 39 experienced at least one PIRA event, defined as sustained increase in Expanded Disability Status Scale scores in the absence of relapses, during the follow-up period. Compared with those without PIRA, these patients had more severe disability and a greater lesion load.
Using advanced MRI scans, the researchers examined the health of white matter tracts in the patients’ brains. They found patients who experienced PIRA showed signs of significantly more extensive damage to white matter in a number of brain regions.
“Our study showed that [people with] MS experiencing PIRA exhibit increased damage in major [white matter] tracts compared with counterparts without PIRA,” the researchers concluded, noting that this difference was clear even after accounting for other clinical factors and demographic differences.
They said these findings “indicate microstructural damage in major [white matter] tracts as a pathologic correlate of PIRA.”
About the Author
