For many years, multiple sclerosis (MS) was viewed largely as a disease of relapses. A person would develop new neurological symptoms, an MRI might show a new area of inflammation, and treatment would focus on preventing the next attack.
We now know that this is only part of the story.
Some people with MS experience gradual neurological changes even when they haven’t had a relapse and their routine MRI scans appear relatively stable. Researchers sometimes describe the ongoing disease activity behind this progression as โsmoldering MS.โ
In relapsing MS, immune cells enter the brain and spinal cord and cause episodes of inflammation that can produce new MRI lesions and clinical relapses. Today’s disease-modifying therapies can be extremely effective at reducing this type of inflammation.
But inflammation may also persist more quietly within the central nervous system. Older MS lesions can remain biologically active around their edges, with immune cells continuing to contribute to tissue injury. These areas are sometimes called chronic active lesions or slowly expanding lesions.
At the same time, damage to nerve fibers and other processes within the brain may gradually accumulate.
Another important concept is PIRA, which stands for progression independent of relapse activity.
PIRA describes a gradual increase in disability that cannot be explained by a recent MS relapse. Someone might notice that walking is becoming a little more difficult, balance isn’t quite as good, or hand coordination has slowly declinedโeven though there hasn’t been a dramatic MS attack.
This has changed how neurologists think about relapsing MS. Progression isn’t necessarily something that begins only after a person develops secondary progressive MS. It can occur much earlier in the disease.
Routine MRI remains one of our most important tools for monitoring MS, but it doesn’t capture everything happening in the brain.A scan may show no obvious new lesions while microscopic inflammation, nerve-fiber injury, brain-volume loss, or activity around older lesions continues.
Researchers are therefore studying additional ways to detect this quieter disease activity. These include advanced MRI techniques and blood biomarkers such as neurofilament light chain (NfL), which can provide information about injury to nerve fibers.
The good news is that our understanding of MS is becoming much more sophisticated.Preventing relapses and new MRI lesions remains extremely important, but neurologists are increasingly looking beyond these traditional measures. Subtle changes in walking, balance, cognition, hand function, fatigue, and other neurological abilities may also provide valuable information about how MS is behaving.
The next generation of MS treatments may go even furtherโtargeting inflammation that persists within the brain and potentially protecting or repairing damaged nerve cells. The goal is no longer simply to prevent the next relapse: it’s to prevent the quiet progression that can occur between relapses as well.
The BeCare MS app can pick up subtle changes on exam before clinicians and patients do.ย This reflects catching subtle changes from this smoldering disease and prompting a proactive rather than reactive treatment approach.ย Be Aware with BeCare.ย Become a driver in your own MS journey