Myelocortical multiple sclerosis (MCMS) is a new subtype of multiple sclerosis (MS). It’s the first kind of MS known to cause nerve cell loss without damaging the myelin in your cerebral white matter. That’s the layer of the brain under gray matter (the outermost brain layer). Myelin is the protective cover around your nerve fibers, or axons.
Injury to this insulation makes it hard for nerve cells to quickly send signals, like telling your legs when to move. But if you have MCMS, harm to the axons themselves may be behind your symptoms.
Scientists consider MS a “heterogeneous” condition. That means there are different root causes for a shared set of signs and symptoms. The discovery of MCMS sheds some light on these differences and may lead to a new approach when it comes to diagnosis and treatment for MS.
What Is Myelocortical MS?
It’s a type of MS that damages or destroys the myelin in your spinal cord and the outer layer of your cerebral cortex, also called gray matter.
Other features of MCMS include:
- Nerve cell loss, or neurodegeneration
- Less thickness in the outer layer of the brain, or cortical thinning
- No white matter lesions
We haven’t known about MCMS very long. Researchers at Cleveland Clinic discovered it only in 2018. They found it when they took magnetic resonance imaging (MRI) scans and physically examined the brains and spinal cords of 100 people with MS who had just died.
Scientists noted that 12 people, or 12% of the group, had MCMS. More research is needed to know how common this subtype is in the general population.
How Is Myelocortical MS Different From Typical MS?
There isn’t one kind of MS that affects everyone. In fact, some experts think it should be considered a syndrome instead of one condition. But some scientists use the term “typical MS” to refer to people who have white matter lesions in their brain.
What sets MCMS apart is that researchers found evidence of nerve cell loss but no trace of these common white matter lesions. That provides new evidence that neurodegeneration and demyelination can be separate events.
Researchers did find lesions in the gray matter tissue in the cerebral cortex. Gray matter is filled with neurons. Those are nerve cells that process information. White matter holds the “wires” that transmit that info throughout your brain and body.
Scientists used to think white matter lesions were the main cause of both nerve cell loss and serious symptoms in people with MS. But there’s growing evidence that a loss of gray matter alone is one of the best ways to predict MS-related disability.
What Are the Symptoms of Myelocortical MS?
Keep in mind that MS is hard to predict, and we need more evidence about this new subtype to know how it affects big groups of people. But people with MCMS had physical issues while they were alive. Scientists think that’s likely due to lesions in the spinal cord.
People with MCMS had some of the following symptoms early on:
Later on, they had symptoms such as:
- Bowel or bladder problems
- Slurred speech and difficulty swallowing
- Lack of coordination
- Blurry vision
- Lower leg paralysis
People with MCMS seem to have fewer changes in mood and thinking compared to those with typical MS. More research is needed to know for sure.
How Is Myelocortical MS Diagnosed?
Scientists don’t yet have a way to identify MCMS in people who are still alive.
MRI scans are still the best way to detect MS lesions in the brain and spinal cord. But right now, this kind of brain imaging doesn’t show a difference between white matter lesions in a typical MS brain and abnormal tissue in someone who has MCMS.
There’s evidence that nerve fibers, or axons, swell in the brains of people with MS. Scientists aren’t sure why this happens, but it seems to mimic white matter lesions on an MRI.
In the future, more sensitive technology may be able to detect certain changes in white matter outside of myelin damage.
What’s the Outlook?
Early research shows MCMS occurs most often in people diagnosed with secondary progressive MS. But there’s evidence that it can happen to people with relapsing-remitting MS and primary progressive MS.
Scientists didn’t find a big difference in terms of age of death and disability between people with MCMS and those with typical MS.
The discovery of this new subtype may lead to different therapies down the road. Doctors may focus less on trying to prevent or repair white matter lesions in this group. Instead, they may:
- Address different pathways that cause nerve cell loss
- Find a way to treat swollen axons
- Use medication to protect nerve cells
- Create different kinds of clinical trials for people with MCMS
Talk to your MS doctor if you think you have any type of MS. They’ll help you find a treatment plan that works for you. Lifestyle changes and drug therapies can help you manage your symptoms and may slow disease progression.