6 Things to Know About MS Brain Lesions
What causes scarring in multiple sclerosis? Why is treatment so important, and do lesions ever heal?
When you have the autoimmune disorder multiple sclerosis (MS), lesions on your brain are part of the package—in fact, the word "sclerosis" means scarring, and scarring is just another way of describing lesions.
“You can’t diagnose MS without having brain lesions in at least two areas of the [central] nervous system, one of which has to be in the brain,” confirms Pavan Bhargava, M.D., assistant professor of neurology at the Johns Hopkins University School of Medicine in Baltimore, MD.
But what, exactly, are they? How do they form? And why do they trigger MS symptoms? Here are the answers to your top questions about MS-related brain lesions.
1. How Do Brain Lesions Form?
Brain lesions are caused by a rogue attack from your body’s own immune system, Dr. Bhargava explains. A lesion, or scarring, forms when your immune cells mistakenly target and damage the protective coating, called myelin, that surrounds your nerve fibers, which are also called axons. (This protective coating works much like cables in your home do, sheathing the live wires within them—and you can imagine what happens when that sheathing gets frayed or destroyed.) The medical term for myelin damage and loss is demyelination. And while lesions from MS are often found on different parts of the brain, they can occur anywhere in your central nervous system (CNS), which also includes the two optic nerves and spinal cord.
“Basically, immune cells in the bloodstream get activated for some reason,” Dr. Bhargava says. “They cross into the brain, are activated again, and then produce substances that bring other immune cells into the brain. This causes damage that ends up forming lesions.” In some cases, these immune cells cut through the actual nerve fibers, causing permanent damage, since severed nerves can’t send or receive signals.
When brain lesions first form, Dr. Bhargava says there is active inflammation that can be seen on a magnetic resonance imaging (MRI) scan. If your doctor suspects you have active lesions, you’ll likely have an MRI with gadolinium contrast, he explains. Gadolinium is a rare earth metal that’s used as a contrasting agent to show areas of recent inflammation in your body. Normally, the contrast can’t get into your brain or spinal cord, thanks to what’s known as the blood-brain barrier. But when lesions are active, they upset the blood-brain barrier's normal defenses. The contrast leaks through to the lesions, and they show up clearly on an MRI.
Over time, the inflammation dies down, the blood-brain barrier goes back to normal, and the contrast no longer shows up on imaging scans. “You’re then left with an area where there’s a loss of myelin, what we call demyelination,” Dr. Bhargava says. You may eventually develop scar tissue in these areas that’s made up of immune cells called microglia.
2. Why Do Lesions Cause MS Symptoms?
The CNS controls everything in your body. So, “wherever the lesions are, they disrupt that signaling pathway,” says Le Hua, M.D., director of the Mellen Program for Multiple Sclerosis at Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas, NV.
If a lesion forms on one of your optic nerves, it affects your vision. If it develops on your spinal cord, you might experience numbness or difficulty moving your arms or legs. If it attacks your brainstem, this can impact your eyes and facial movements, speech, and even swallowing. Lesions can also cause fatigue and brain fog, Dr. Hua says.
MS is a relapsing-remitting disease, which means you have periods of disease activity (relapse), followed by periods where inflammation decreases and disease activity stops (remission). “All the symptoms that we typically associate with MS relapses … can be caused by lesions, depending on where they are,” says Dr. Bhargava. “As the inflammation dies down in those lesions, the symptoms can then improve.”
3. Are Lesions on the Brainstem More Serious?
Where, exactly, lesions show up can make a difference, according to Dr. Hua. Lesions in your brainstem or spinal cord are associated with more physical symptoms and a higher risk of disability than lesions that form in other parts of the brain.
He offers an analogy: “If you think about streets, if you block off a road in a neighborhood, there’s not going to be a lot of impact,” Dr. Hua says. “But as those roads and pathways come together in the brainstem and then in the spinal cord, now you’re on a highway. If you block off the highway, you’ve caused significant problems.”
In other words, depending on where it’s located, a lesion in your brain might not affect you that much. You might not even have any symptoms. This is called a silent lesion. Dr. Bhargava says that oftentimes, when people come in with their first relapse from lesions on the optic nerve or spinal cord, “we find that they actually have 10 or 15 lesions in the brain, none of which ever caused any symptoms before,” he says.
Keep in mind, too, that where a lesion appears doesn’t necessarily indicate how much you’ll improve once inflammation decreases after a relapse, notes Dr. Bhargava. How well you bounce back depends more on the lesion’s size and how severe the damage was in the first place.
He also points out that the number of lesions you have doesn’t always correlate with how severe your disease is, or how much MS affects you. “There are some people who have lots of lesions and have very few symptoms, while others can have just a handful of lesions and be really affected by them,” he explains. Again, it depends on where the lesions are located, plus the amount of damage caused.
4. Can Lesions Be Slowed Down or Prevented?
The goal of MS treatment, then, is to stop relapses from occurring: “We prevent new relapses by preventing new lesions from forming,” explains Dr. Bhargava.
Disease-modifying MS therapies, such as beta interferon drugs, infusion treatments, and oral medications, have been shown to be powerfully effective when it comes to preventing new lesions. These treatments can reduce existing inflammation, too.
“We can slow down the inflammation of some lesions when they’re actively inflamed by starting therapy so the lesion itself might not be as drastic,” Dr. Hua says.
5. Can Lesions Heal Once They Appear?
“Absolutely,” says Dr. Hua. “It’s not specific to MS, but in any process where there’s some sort of brain injury, there will always be healing, as well. There will also be the formation of scar tissue,” a process called gliosis, he adds.
In some people, myelin in the lesions is actually repaired to some degree, known as remyelination. However, “it won’t be as robust as the original,” Dr. Hua says, meaning you may gain back some nerve functionality over time, but perhaps not all.
Pathology reports on the brains of deceased people with MS have shown that some lesions appear to show remyelination, agrees Dr. Bhargava. “It does seem that the body can at least partially heal some of these lesions, but this may vary from person to person, and then from lesion to lesion within the same brain,” he says.
Research is in the works to find ways to help the nervous system repair damaged myelin. Scientists are looking into options such as stem cell therapy and certain medications such as clemastine (an oral antihistamine), lipoic acid (an antioxidant), ibudilast (anti-inflammatory), and phenytoin (epilepsy drug) that show promise.
6. Why Is It Important to Monitor MS Lesions?
Dr. Hua says that lesions show up much more frequently on MRI than they do clinically (the aforementioned “silent” lesions.). This is why doctors monitor MS with frequent MRI scans instead of waiting for patients to present with symptoms. “We want to see the silent disease activity. We want to make sure that no new lesions are formed, because if we can stop lesion formation, we will significantly reduce disability,” says Dr. Hua.
MRIs are typically done every year, he explains. If you’ve started a new medication, Dr. Hua says you might have one in six months's time to make sure the medication is doing its job. Once you’re older, inflammation tends to slow down. You won’t need MRIs as often as long as your MS is stable.
Though MRI scans are an important tool doctors use to monitor MS, they don’t provide the whole picture. “We still rely on clinical tools, other tests, and other measures to really help us understand the best way to care for patients,” Dr. Hua says.
Diagnosing MS: Brain: A Journal of Neurology. (2019.) “Assessment of lesions on magnetic resonance imaging in multiple sclerosis: practical guidelines.” ncbi.nlm.nih.gov/pmc/articles/PMC6598631/
Gadolinium: U.S. Food and Drug Administration. (2018.) “Information on Gadolinium-Based Contrast Agents.” fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/information-gadolinium-based-contrast-agents
Blood-Brain Barrier: National Multiple Sclerosis Society. (n.d.) “Magnetic Resonance Imaging (MRI).” nationalmssociety.org/Symptoms-Diagnosis/Diagnosing-Tools/MRI
Disease-Modifying Therapies: National Institute of Neurological Disorders and Stroke (NINDS). (2021.) “Multiple Sclerosis: Hope Through Research: Disease-modifying treatments.” ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Multiple-Sclerosis-Hope-Through-Research#attacks
Myelin Repair Research: National Multiple Sclerosis Society. (n.d.) “Repairing Damaged Tissues.” nationalmssociety.org/Research/Research-We-Fund/Restoring-What-s-Been-Lost/Repairing-Damaged-Tissues