Duchenne muscular dystrophy (DMD) is a genetic condition that causes progressive muscle weakness. Many people know that DMD can lead to heart and lung complications, but fewer are aware of its effects on the brain. When DMD affects the brain, it can result in cognitive (thinking and memory) problems and psychological (emotional) problems.

Continue reading to learn more about how DMD can affect the brain and the symptoms it can cause.

How Does DMD Affect the Brain?

Although DMD mostly affects the skeletal (voluntary) muscles, it also impacts other parts of the body that contain dystrophin — a protein that helps muscles work properly and repair damage.

In DMD, a mutation (change) in the DMD gene (or dystrophin gene) disrupts the body's ability to produce dystrophin, leading to low or absent dystrophin levels. Without this protein, muscles become weaker over time and struggle to repair themselves properly.

Although dystrophin is mostly found in the skeletal muscles, it is also present in other body tissues, including:

• Neurons (brain cells)
• Cardiac (heart) muscle
• Smooth muscle (involuntary muscles, such as those in the digestive system)
• Endocrine glands (which produce hormones)

Other neuromuscular conditions, such as Becker muscular dystrophy, congenital muscular dystrophy, and myotonic dystrophy, can also affect the brain.

Researchers are still working to understand how and why DMD gene mutations impact brain function. Health specialists believe that brain-related symptoms in DMD may result from dystrophin deficiency and inflammation linked to the condition.

Dystrophin Deficiency in the Brain

Many parts of the brain and central nervous system (CNS) contain dystrophin protein. In fact, some types of dystrophin proteins are found only in the CNS.

In the brain, dystrophin plays a role in helping neurons communicate and supporting other brain cells that help neurons work properly. Unlike in muscle cells, dystrophin in the brain is not believed to protect against mechanical damage (physical damage or injury). Additionally, brain cells produce only about one-tenth of the amount of dystrophin found in skeletal muscle cells.

Clinical studies in humans and animals suggest that the same DMD gene mutations that cause muscle weakness may also disrupt dystrophin’s role in the brain.

Inflammation

DMD can cause chronic (long-term) inflammation all over the body. Researchers think that chronic inflammation may also contribute to cognitive impairment in DMD.

Inflammation in DMD occurs because muscle cells are more prone to damage without the dystrophin protein. Tissue damage activates your immune system’s inflammation response — your body’s natural response to injury.

In DMD, progressive muscle damage causes chronic inflammation all over the body. During inflammation, damaged muscle cells release inflammatory substances called cytokines. These cytokines can have a direct effect on the brain. When cytokine levels are high for a long period of time, neurons in the brain may not work as well.

What Are the Signs of DMD Affecting the Brain?

DMD can impact the brain in several ways. In this section, we’ll review some possible symptoms that may occur when DMD affects the brain.

Developmental Delays

A developmental delay is when a child takes longer to achieve developmental milestones. Healthcare providers can monitor a child’s progress by comparing when they reach certain developmental milestones compared to other children.

Children with DMD may take longer to develop certain skills, such as:

• Sitting
• Walking
• Running
• Speaking
• Grasping small objects or using utensils
• Potty training

Intellectual Developmental Disorder

People with DMD have a wide range of intellectual abilities, just like the general population. Intellectual ability is commonly measured by an IQ test. Though most people with DMD have an IQ within the typical range, children with the condition have a higher risk for below-average IQ, also known as intellectual developmental disorder. It’s estimated that about 22 percent of people with DMD have an intellectual disability.

Researchers are still learning about how DMD can affect IQ. They’ve found that some variants of DMD gene mutations are more commonly associated with lower IQ in DMD than others.

Language Problems

Some people with DMD have difficulty understanding complex information that’s given to them verbally. Others may have trouble expressing their ideas clearly to others. These language challenges can sometimes be mistaken for a child not following instructions or being forgetful.

Learning Disability

Learning disabilities can occur in DMD due to changes in how the brain processes certain information. People with DMD may have problems with their verbal short-term memory or their working memory. Verbal short-term memory refers to the amount of new information you can keep in mind at once. Working memory is the ability to work with information without losing track of what you’re doing.

Language problems can put children with DMD at risk of developing a learning disability, such as dyslexia. People with dyslexia have differences in the way their brain processes written language. In DMD, language problems and differences in short-term memory can lead to reading problems. Dyscalculia (difficulties with math) and dysgraphia (difficulties with writing) are also more common in children with DMD.

It’s important to note that learning disabilities don’t affect intelligence.

Neurodevelopmental Disorders

Neurodevelopmental disorders are conditions that affect brain development and can impact learning, behavior, and social skills. Children with DMD are slightly more likely than the general population to have a neurodevelopmental disorder, such as:

• Attention-deficit/hyperactivity disorder (ADHD) — A condition that causes problems with attention, hyperactivity, and impulse control
• Autism spectrum disorder (ASD) — A condition that affects how a person interacts, communicates, and experiences the world around them

Research suggests that about 18 percent of people with DMD have ADHD and 6 percent have ASD.

Anxiety

Anxiety disorders are more common in people with DMD compared to the general population. It’s estimated that between 24 percent to 33 percent of people with DMD also have an anxiety disorder. Anxiety disorders may include obsessive-compulsive disorder (OCD), panic disorder, or phobias. Researchers think that a lack of dystrophin in the brain may increase the risk of anxiety.

Diagnosing and Managing DMD Symptoms of the Brain

Healthcare providers may have a hard time determining whether a neurological difference or other brain symptom is due to DMD or another cause. Additionally, there are no diagnostic tests specifically designed to assess brain-related symptoms in people with DMD.

Because DMD is rare, there isn’t much clinical research on the best way to manage brain disorders related to the condition. New therapies for DMD — such as gene therapy — have revolutionized DMD treatment. However, the gene therapies that are currently available don’t target the brain. Future DMD treatments may be able to improve some brain-related symptoms.

Examples of interventions to consider in your DMD treatment plan include:

• Speech therapy — Helps with speech, language, and communication challenges, including difficulty expressing thoughts or understanding spoken information
• Occupational therapy — Supports the development of fine-motor skills (such as writing or using utensils) and helps with daily activities like dressing or using assistive devices
• Physical therapy — Aims to improve mobility, muscle function, and coordination while preventing joint stiffness and contractures
• Cognitive behavioral therapy (CBT) — A type of talk therapy that can help with emotional regulation, anxiety, and adapting to challenges related to DMD
• Educational support — Provides accommodations, specialized instruction, or individualized learning plans to help children with DMD succeed in school

Your healthcare team can help develop a treatment plan based on your symptoms and preferences.

Medications

The effects of medications for neurodevelopmental disorders or anxiety haven’t been well studied in people with DMD. As a result, there aren’t any treatment recommendations from health specialists.

Some studies have found that some mental health conditions in people with DMD do improve with medications. A few small studies have shown that methylphenidate (Ritalin) improves ADHD symptoms in people with DMD. Additionally, selective serotonin reuptake inhibitors (SSRIs) have been shown to improve anxiety and OCD symptoms in people with DMD.

Before starting any new medication, it’s important to consider the side effects that may affect the heart and lungs. While there haven’t been any studies showing that medications are harmful in people with DMD, some side effects may cause issues for people with DMD. For example, methylphenidate can cause hypertension (high blood pressure) and changes in heart rhythm. SSRI medications can decrease in blood pressure and heart rate.

Talk to your healthcare team about the risks and benefits of starting a new medication, and let them know if you experience any side effects or concerning symptoms.

Talk With Others Who Understand

On myMDteam, the site for people with muscular dystrophy (MD) and their loved ones, members come together to gain a new understanding of MD and share their stories with others who understand life with the condition.

Do you or a loved one have any brain-related symptoms of DMD? What interventions or treatments have helped you cope? Share your experiences in the comments below, post to your Activities page, or connect with like-minded members in Groups.