MS Brain Scans Reveal How Often Slow-Growing Lesions Show Up

Doctors have long noticed that multiple sclerosis leaves behind more than just scars in the brain. Some lesions, known as slowly expanding lesions, quietly grow over time. They form a small part of the overall damage but appear in most patients with the disease.

A large review looked at MRI scans from thousands of people with MS. Researchers gathered data from twenty different studies covering nearly five thousand patients. The average age was around forty-three, and most patients were women. The goal was simple: figure out how common these slow-growing lesions really are.

The numbers tell a striking story. Only about fourteen percent of all visible lesions on T2 scans fall into the slow-expanding category. Yet roughly seventy-eight percent of patients have at least one of these lesions hiding in their brain. Their average volume stays small, around 1.4 milliliters, compared to the total T2 lesion volume of about ten milliliters.

Another type of chronic lesion, called paramagnetic rim lesions, gets attention too. Only about eleven percent of slow-expanding lesions overlap with these rim lesions. That gap matters because it suggests the two types may track different kinds of brain inflammation. Patients with progressive forms of MS also tend to carry more slow-expanding lesions than those with relapsing forms, even though the per-lesion rates look similar.

The findings could push doctors to rethink how MRI scans are read. Slow expansion might serve as a warning sign of ongoing damage, even when other markers look stable. Researchers still need clearer ways to define these lesions and track them across diverse patient groups. The message is clear: not all MS lesions behave the same, and recognizing that difference could sharpen future treatment decisions.