Scientists don’t know exactly why certain people with MS have more lesions in their brain or spinal cord. What they do know, says Dr. Reder, is that spinal cord lesions “are more common in the more progressive forms of MS” than in other forms of MS. And in cases with spinal cord damage, there are sometimes actually fewer brain lesions, he adds.
Researchers, too, have knowledge gaps about this feature of the disease. Filling these gaps may lead to a better understanding of progressive forms of multiple sclerosis.
Spinal cord lesions in MS “probably” form through the same mechanisms as those in the brain, says Reder.
“For some unknown reason, white blood cells escape from the bloodstream, go through the blood-brain barrier, and get into the brain tissue,” he explains. These cells cause inflammation of the brain and spinal cord — mostly in the white matter, but also the gray matter.
According to Reder, toxic chemicals produced by these cells strip the myelin insulation off the connections between nerves. The resulting lesions tend to affect multiple nerves and tend to be 1 to 2 centimeters in length or diameter.
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