Multiple Sclerosis: A Subtype Called Myelocortical MS

Nerve cell loss may occur independently from myelin loss

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The story of multiple sclerosis (MS) is ever-changing, unfolding, and keeping us on our toes—and this continues to hold true, as scientists at the Cleveland Clinic discover a new MS subtype.

Before understanding how this MS subtype came to fruition though, it's important to quickly review the basic pathophysiology of MS, which refers to the abnormal processes that occur within the brains and spinal cords of those with MS.

Pathophysiology of Multiple Sclerosis

When you delve into the details behind "why" MS lesions (those white spots on your MRI) arise, you will inevitably read about a process called demyelination, which refers to the loss of the myelin sheath (the fatty covering that insulates nerve fibers).

White Matter Demyelination

In MS, white matter demyelination is believed to occur as a result of an autoimmune attack, meaning a person's own immune system misguidedly attacks myelin within the deeper white matter areas of the brain.

With damaged myelin, nerve signals cannot be transmitted rapidly or effectively, leading to a variety of symptoms, depending on where in the brain or spinal cord the attack is occurring.

Nerve Cell Death

With the loss of myelin in MS, nerve cells may eventually die (called neuronal loss), leading to irreversible disability. However, and this is key, it was always believed that nerve cell loss only occurred in the presence of myelin loss. In other words, the destruction of myelin was believed to trigger the eventual death of a nerve cell.

Two Independent Processes

This is proving to be wrong, though. In a study in Lancet Neurology, investigators found that nerve cell loss may occur independently from demyelination—and this phenomenon is significant enough to be named its own MS subtype, myelocortical MS.

How Myelocortical MS Was Discovered

In the study in Lancet Neurology, investigators examined the brains and spinal cords of one hundred deceased patients with MS.

During their analysis, the investigators found that twelve of the MS patients did not have demyelination in the white matter areas of their brain (only in the spinal cord and the cerebral cortex, which is the outer layer of the brain).

This is remarkable, considering white matter demyelination, as stated earlier, is the hallmark feature behind MS, or the "why" behind how MS lesions form.

You may wonder then why people with "myelocortical MS" had typical white matter MS lesions on their brain MRIs (when they were alive). The study authors aren't totally sure, but they suggest that swollen, dying nerve cells must resemble white matter myelin loss on MRI. As a result, only through autopsy can one diagnose myelocortical MS.

What Does This Mean For Me?

Aside from gaining deeper knowledge about the pathophysiology of MS, this finding—that nerve cell loss can occur independently from myelin loss—will hopefully spark some next steps for MS researchers.

For example, it may inspire improved brain MRI techniques for analyzing subtle nerve cell changes. This way experts may be able to more easily diagnosis and predict the course or prognosis of a person's MS.

By dividing MS into subtypes, researchers may be able to better target therapies—taking a more individualized approach to MS care.

All this said, keep in mind, we do not know the prevalence of people with myelocortical MS versus traditional relapsing-remitting MS.

In the study, there were 12 patients (out of 100) with myelocortical MS. However, all of the deceased patients in the study had died of complications from advanced MS. It's difficult, therefore, to compare the study MS population with the real world MS population.

Regardless, even if those with myelocortical MS make up only a small population, this discovery will likely have worthy implications for everyone with MS.

A Word From Verywell

The big picture here is that experts are getting closer to teasing out the biology behind MS, which is proving, perhaps, to be just as unique a disease in its mechanism of action as it is in its symptoms.

In the end, the discovery of an MS subtype brings us one step closer to finding a cure—a hope that we all cling to and live for each day.

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Article Sources

  • Trapp BD et al. Cortical neuronal densities and cerebral white matter demyelination in multiple sclerosis: a retrospective study. Lancet Neurol. 2018 Aug 21 pii: S1474-4422(18)30245-X. DOI: 10.1016/S1474-4422(18)30245-X.