Lesions in multiple sclerosis (MS) occur when the immune system attacks the central nervous system (CNS), which includes the brain, optic nerve, and spinal cord. The term “sclerosis” refers to the scar tissue that forms in these lesions, also called plaques or scleroses, a hallmark of MS. This scarring results from damage to the myelin sheath — a fatty tissue that insulates nerve fibers — and the inflammation that defines the condition.

In people with MS, lesions most commonly develop in the brainstem, cerebellum, spinal cord, and optic nerve. They may be confined to a single area, scattered across multiple locations, or affect extensive regions of the CNS.

Causes of Brain Lesions

Brain lesions can occur for many reasons. Brain trauma, viral or bacterial infections, age, or a family history of brain lesions may play a role. Autoimmune diseases, such as lupus — and multiple sclerosis — can also lead to the development of brain lesions. In the case of MS, brain lesions result from inflammation and damage caused by a misfiring immune response and the formation of scar tissue.

Brain Lesions and MS Symptoms

Symptoms of MS vary from person to person and depend on where MS lesions develop in the central nervous system. The severity, size, and location of lesions all depend on disease activity and determine which functions of the central nervous system are affected.

Frontal Lobe

The frontal lobes — the largest of the brain’s lobes — are located immediately behind the forehead. The frontal lobes contain the motor area, which is responsible for voluntary movement. They also control memory, intelligence, reasoning, concentration, and aspects of your personality. Lesions on the frontal lobe can cause symptoms including speech impairment, loss of motor function on one or both sides of the body, and changes in mood or behavior.

Parietal Lobe

The parietal lobes are at the center of the brain and process sensory information. Your parietal lobes allow you to feel temperature, taste, touch, and movement, and they’re also important for reading and doing math. Lesions in the parietal lobes may cause symptoms such as forgetting words for common objects and loss of sensations such as heat, cold, and pain. The parietal lobe also carries a portion of the nerve fibers originating from the eyes, so lesions in this area can affect the lower part of the visual field.

Occipital Lobe

The occipital lobes are located at the back of the brain. Their job is to process images from the eyes and link that information with images stored in memory. Essentially, your occipital lobes enable you to identify what you’re seeing. Lesions in the occipital lobes may cause changes in your vision.

Temporal Lobe

The temporal lobes are located in the center of the brain — specifically, they’re in front of the occipital lobes and beneath the parietal and frontal lobes. Temporal lobes play a large role in integrating the senses of hearing, touch, and smell, and they’re key to forming and storing memories.

Lesions in the temporal lobes can result in cognitive symptoms, including moodiness, forgetfulness, and difficulty focusing. Sensory symptoms, such as loss of taste, smell, and hearing, can be symptomatic of lesions in this part of the brain, as can changes in behavior, mood, and emotions. The temporal lobes also carry optic fibers, and lesions in this area can cause problems with the upper field of vision.

Brain lesions don’t always cause noticeable symptoms, especially in the case of early phases of different types of MS. If these so-called silent lesions get worse over time, symptoms become more noticeable.

Tools Doctors Use To Detect Brain Lesions

In some instances, lesions or their symptoms are detected during an exam, a scan, or routine monitoring for an unrelated condition. Other times, neurologic symptoms bring a person to the doctor’s office, and then image testing, cerebrospinal fluid analysis, and blood tests result in a diagnosis of MS or clinically isolated syndrome.

The first step in diagnosing lesions in the brain may involve a neurologist taking a complete medical history, conducting a physical examination, and performing a detailed neurological exam. The doctor may:

• Test your strength
• Use vibration or hot or cold objects to assess your ability to detect sensations
• Gently touch a sharp object to your skin or pinch your cheek or another part of your body to check pain responses

These stimulus response tests may also help pinpoint the location of the lesion or lesions.

Diagnostic Imaging Tests for MS Lesions

Computed tomography (CT) is a type of neuroimaging (brain and spinal cord imaging) technology that uses radiation to take images of brain tissue. A solution may be injected into a person’s vein to help highlight brain structures. CT scans can be used to diagnose brain lesions.

Magnetic resonance imaging (MRI) is a noninvasive diagnostic tool that uses magnetic fields and computer technology to produce 3D images of the brain. An MRI scan shows greater detail in brain tissue, the cerebellum, and the brainstem than a CT scan. Brain lesions appear as darker or lighter spots on an MRI scan, and the findings are important for making a diagnosis.

MRI conducted with a contrast fluid called gadolinium can show whether the lesions are active (recent) and if there’s evidence of preexisting inflammation or lesions. If lesions don’t appear brighter on a high-contrast MRI, they are likely not new lesions and are older than three months.

The type, size, and distribution of brain lesions in MS are also an important part of the McDonald criteria — the set of diagnostic criteria developed by an international panel of experts that’s most frequently used to diagnose MS.

If you or your health care provider suspects your symptoms may be related to brain lesions, prompt attention is your best bet. A timely, thorough evaluation by a neurologist with specialized training is very important to identify the presence of a lesion and determine the potential underlying cause. From there, your doctor can recommend the most appropriate treatment plan.

Prevention of New or Worsening MS Lesions

The U.S. Food and Drug Administration (FDA) has approved more than two dozen disease-modifying therapies (DMTs) to treat relapsing or progressive MS. Different treatments for MS have varying mechanisms of action, which include:

• Reducing inflammation and demyelination (damage to and destruction of myelin)
• Managing the response of immune system cells
• Lowering the quantities of certain immune system cells involved in demyelinating MS attacks

Highly effective (HE) DMTs have been found to be especially good at slowing disease and disability progression in some people. HE DMTs include:

• Alemtuzumab (sold as Lemtrada)
• Cladribine (Mavenclad)
• Fingolimod (Gilenya, Tascenso ODT)
• Mitoxantrone (Novantrone)
• Natalizumab (Tysabri) and its biosimilars, such as natalizumab-sztn (Tyruko)
• Ocrelizumab (Ocrevus)
• Ofatumumab (Kesimpta)
• Ozanimod (Zeposia)
• Rituximab (Rituxan, MabThera, and Truxima) — Rituximab is not currently indicated for treating MS but is frequently prescribed “off-label.”
• Siponimod (Mayzent)
• Ublituximab-xiiy (Briumvi)

Over time, you may switch treatments for MS for various reasons, including:

• Changes in disease activity or progression
• Development of side effects or intolerances
• Lack of effectiveness of the current therapy
• Advancements in new or more effective treatment options

Other Ways To Keep Your Brain Healthy

Multiple sclerosis is a chronic illness with no known cure. Regular monitoring and follow-up care are important parts of tracking and managing disease progression. Brain lesions can be caused or worsened by factors other than MS, such as aging or stroke. Maintaining a generally healthy lifestyle, including eating nutritious foods and being physically active, can go a long way toward keeping your brain functioning smoothly, whether or not you have MS.

If You Smoke, Stop

Toxins in cigarette smoke can worsen brain lesions and their symptoms. Studies have shown that people who smoke are more likely to develop MS. In a 2022 study of 85 people with MS, researchers reported that those who smoked had a higher lesion volume (more damaged brain tissue) after 10 years, adding that further MS research into a possible link between smoking and lesions is needed. Talk to your health care provider if you smoke and need help quitting.

Make Healthy Lifestyle Changes

If you’re living with MS, strategies like the following can also help keep your brain healthy and limit your risk of new or worsening brain lesions caused by other factors:

• Control your blood pressure — Vascular (affecting blood vessels) disease and issues such as stroke and high blood pressure can cause lesions in the brain.
• Choose heart-healthy foods — Diets high in excess fats have been linked to lesions in the brain. Following a low-fat, low-cholesterol diet can reduce the likelihood of more lesions.
• Wear a helmet when riding a bike or playing contact sports — Traumatic brain injury can cause or worsen lesions.

Talk With Others Who Understand

On MyMSTeam, the online community for those living with multiple sclerosis and their loved ones, more than 217,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS. Brain lesions are a frequent topic of conversation among MyMSTeam members.

Do you have questions about brain lesions and MS? What strategies do you follow to keep your brain healthy? Share your thoughts in the comments below, start a new conversation on your Activities page, or connect with like-minded members in Groups.