New study links specific MRI lesion pattern to MS risk before symptoms
Paramagnetic rim lesions tied to higher risk of MS symptoms
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An MRI scan being performed as a technician reviews brain imaging. (Photo from iStock)
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Paramagnetic rim lesions (PRLs) on MRI are associated with a higher risk of developing clinical multiple sclerosis in people with radiologically isolated syndrome (RIS).
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Higher PRL counts at RIS diagnosis are associated with a shorter time to developing MS symptoms.
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PRLs may serve as a potential prognostic biomarker to help identify higher-risk RIS patients.
A specific pattern of damage seen on MRI scans, called a paramagnetic rim lesion, is associated with a higher risk of developing overt multiple sclerosis (MS) in people who have MS-like brain lesions but no symptoms, according to a new study.
This condition is known as radiologically isolated syndrome (RIS), which refers to people who have MS-like lesions on MRI but no neurological symptoms. Researchers said the findings suggest these lesions could help identify higher-risk individuals in the earliest stages of MS, even when patients are not yet showing symptoms.
The study, “Paramagnetic Rim Lesions and Development of Clinical MS in Radiologically Isolated Syndrome,” was published in JAMA Neurology.
What paramagnetic rim lesions reveal about MS
MS is marked by inflammation that damages the brain and spinal cord. This damage appears on MRI scans as spots known as lesions. Paramagnetic rim lesions, or PRLs, are a specific type of lesion marked by a rim of iron-laden immune cells — mainly microglia and macrophages — surrounding damaged nerve tissue. These lesions are highly indicative of MS and may help distinguish it from some similar conditions.
Sometimes, MRI scans reveal MS-like lesions in people who do not have any neurological symptoms. Studies suggest that roughly half of people with RIS develop overt MS symptoms within 10 years, while others may never develop symptoms.
Historically, people with RIS were not diagnosed with MS unless they developed symptoms. Under recently revised diagnostic guidelines, some individuals may now meet criteria for MS based on additional clinical or imaging findings.
In recent years, clinical trials have shown that some MS treatments may reduce the risk of developing overt symptoms in people with RIS. However, because not all individuals with RIS will develop MS, researchers are working to identify those at highest risk who may benefit from available disease-modifying therapies.
The researchers had previously found that many people with RIS have at least one PRL. They therefore examined whether PRLs could serve as a marker of future risk for developing clinical symptoms.
“PRLs have gained attention as a specific MRI biomarker and imaging measure of progression-related biology in MS,” the scientists noted.
Researchers analyze whether PRLs predict MS symptoms
To investigate further, the researchers analyzed outcomes from two groups of people with RIS, totaling 79 participants. Over median follow-up periods of about 4 to 6 years, 18 participants developed overt MS symptoms.
In the first group, higher PRL counts were significantly associated with an increased risk of developing clinical MS symptoms.
In the second group, PRL count itself was not significantly associated with symptom risk. However, participants with at least one PRL had about 20 times the odds of developing MS symptoms compared with those without any of those lesions.
In both groups, a higher number of PRLs at the time of the RIS diagnosis was significantly associated with a shorter time to developing symptoms during the 5- to 30-year period following diagnosis.
“Higher PRL counts were associated with a shorter time to developing symptoms in both cohorts, although defining an optimal threshold remains challenging,” the researchers wrote.
Study limitations may explain differences between groups
The researchers noted that technical differences between the two groups, as well as the small sample size and limited number of participants who developed symptoms, may help explain why results were not fully consistent across cohorts.
Despite these limitations, the researchers emphasized that PRLs were significantly associated with the risk of developing clinically definite MS across the two cohorts. Together with prior research in people with established MS, they said the findings support PRLs as a potential prognostic biomarker in RIS, though further studies are needed before they can be used routinely to guide care.
“As PRLs reflect a subset of chronic active lesions, our findings, together with prior data from people with MS, support their value as a prognostic biomarker for risk stratification and therapeutic decision-making in people with RIS and across the MS spectrum,” the scientists concluded.
