Muscular Dystrophy and Neuromuscular Diseases

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What are muscular dystrophy and neuromuscular diseases?

Muscular dystrophy (MD) is a group of rare neuromuscular diseases that cause weakness, wasting away of muscles, and permanent loss of muscle tissue. MD is a progressive disease and symptoms get worse over time. Muscles degenerate, causing communication problems between the muscles and nerves that control movement. MD can also cause spasms, twitching, and pain, as well as heart and lung problems. 

Most types of MD are caused by a new mutation (change) in your genes, or a mutation that’s inherited from your parents. Some forms of MD develop in infancy or childhood; others appear in middle age or later. Medications and therapy can help manage symptoms, slow the disease’s progression, help maintain mobility, and lengthen lifespan.

Are there different types of muscular dystrophy?

 There are more than 30 types of MD. Each type can differ according to which muscles are affected, the extent of muscle weakness, age of onset, rate of progression, and if they’re inherited.

The most commonly occurring types are:

Duchenne MD develops primarily in boys between ages 2 to 6. Survival beyond the 20s is rare because of the diseases’ rapid progression. Most boys can no longer walk by age 12, and later need a respirator to breathe. Girls in these families have a 50% chance of inheriting the defective gene and passing it to their children. Duchenne is the most common type of MD, and includes general muscle weakness, and muscle wasting that initially affect the pelvis, upper arms and legs. It can affect a child’s heart and lungs. Eventually all voluntary muscles are affected. 

Becker MD, the second most common MD, develops between the ages of 5 and 60, but usually in the teen years. It affects the hip, thigh and shoulder muscles, and eventually the heart. Symptoms are the same as Duchenne but milder, and it progresses more slowly than Duchenne. Most patients diagnosed young can survive to middle age.  

Congenital MD is present at birth. Symptoms can include muscle weakness, a curved spine, joints that are too stiff or too loose, learning disabilities, seizures and vision problems. It progresses slowly, and can shorten life span.

Distal MD develops between ages 40 to 60. Symptoms include weakness and muscle wasting of the hands, forearms, and lower legs. It progresses slowly and rarely causes total disability. 

Emery-Dreifuss MD develops in childhood to adolescence. Symptoms include weakness and wasting of shoulder, upper arm, and calf muscles. The heart is also affected, and joint deformities are common. It progresses slowly, but heart problems can cause sudden death.

Facioscapulohumeral MD can develop in childhood to early adulthood. Symptoms, which usually appear before age 20, include muscle weakness in the face, shoulder blades, legs, and upper arms. Muscle wasting occurs in the shoulders and upper arms. Disease progression is slow, and symptoms can range from mild to disabling.

Limb-Girdle MD can develop between pre-teenage to middle age. The symptoms first include weakness and wasting of the shoulders and pelvic area. Progression is slow; death is usually due to heart-lung complications.

Myotonic MD, the most common adult form of MD, develops between the ages of 20 to 40, primarily in people of European descent. All muscle groups become weak. Muscle relaxation is delayed after each contraction. It also causes muscle spasms, cataracts, heart/lung  problems, and endocrine disturbances. Muscles of the face, feet, hands, and neck are first affected, causing a long, thin face, drooping eyelids and a swan-like neck. Disease progression is slow and lifespan is shortened.

Oculopharyngeal MD is rare and develops between ages 40 to 70. Muscles of the eyelids and throat are affected, causing weakening of throat muscles. Patients lose the ability to swallow and lose weight, but the progression is slow.

Are there different types of other neuromuscular diseases?

There are many types of neuromuscular diseases, including:

  • Spinal muscular atrophies (muscle wasting), such as ALS, and other atrophies that occur in infants, juveniles or adults
  • Inflammatory myopathies (muscle disease), including dermatomyositis and polymyositis
  • Peripheral nerve diseases (affects nerves that relay information between the brain and body), such as Friedreich’s ataxia, Dejerine-Sottas disease, Charcot-Marie tooth disease
  • Neuromuscular junction diseases (where electrical impulses activate muscles), such as Myasthenia gravis, botulism, Lambert-Eaton syndrome
  • Metabolic diseases of the muscles including enzyme deficiencies and myopathies

Causes

What causes muscular dystrophy and neuromuscular diseases?

Most neuromuscular diseases and MDs are caused by genetic mutations that interfere with the production of proteins, which are needed to form healthy muscle. The faulty gene can come from one or both parents, even if the parent doesn’t have MD. Some types are autoimmune diseases, caused when the immune system mistakenly attacks healthy cells. Although rare, MD can develop spontaneously with no known cause. Each type of MD is caused by a different gene mutation that's unique to that type of disease.

Who’s at risk for muscular dystrophy and neuromuscular diseases?

MD can occur in men or women of any age or race. The most common types develop in young boys. If you have a family history of MD, you have a higher risk of developing it, or passing it on to your children. It’s also possible to have the mutated gene but not have MD (called being a “carrier”). Carriers can pass the mutated gene to their child, who may or may not develop the disease.

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Symptoms

What are the symptoms of muscular dystrophy and neuromuscular diseases?

The main symptom of MD is progressively worsening muscle weakness. As the disease progresses, you may also develop:

  • Choking or swallowing problems
  • Walking difficulties
  • Restricted flexibility and mobility of joints
  • Problems using the arms and shoulders
  • Shortening of muscles or tendons around joints (contractures) that limit mobility
  • Curved spine (scoliosis) from weakening muscles that can’t hold the spine straight
  • Heart problems, such as arrhythmias and heart failure because of reduced efficiency of heart muscle
  • Lung infections, including pneumonia
  • Breathing problems

Specific symptoms that are unique to each type of MD, can include:

Duchenne MD symptoms include:

  • Frequent falls
  • Difficulty rising from a lying or sitting position
  • Trouble running and jumping
  • Waddling gait
  • Walking on the toes
  • Large calf muscles
  • Muscle pain and stiffness
  • Learning disabilities
  • Delayed growth

Congenital MD can cause either a slowly progressing disease and mild disability, or rapidly progressing disease and severe impairment.

Facioscapulohumeral MD first weakens the muscles in the face, hips and shoulders. Shoulder blades might stick out like wings when arms are raised. 

Limb-girdle MD first affects the hip and shoulder muscles. Patients may have difficulty lifting the front part of the foot, causing frequent tripping or stumbling.

Myotonic MD patients can’t relax muscles following a contraction, such as being unable to let go of your hand. Face and neck muscles are the first affected, causing a long, thin face, drooping eyelids, and swan-like necks.

Diagnosis

How are muscular dystrophy and neuromuscular diseases diagnosed?

Your doctor will take your medical history and conduct a physical exam. Others tests may be recommended, including:

  • Enzyme tests that measure enzymes released by damaged muscles. High levels of creatine kinase in your blood suggests muscle disease.
  • Genetic tests examine blood samples for gene mutations linked to MD.
  • Muscle biopsy looks for cell changes in muscle tissue and can distinguish MD from other muscle diseases.
  • Electrocardiogram and echocardiogram are tests that check heart function.
  • Lung-monitoring tests check lung function.
  • Electromyography measures electrical activity as you tighten and relax muscles.
  • Nerve conduction tests measure how fast and how well electrical signals travel down your nerves.

Receiving a diagnosis of MD or other neuromuscular disease can be extremely challenging. It’s important to provide emotional support to patients as well as medical care.

Treatment

How are muscular dystrophy and neuromuscular diseases treated?

Although there's no cure for any form of MD, treatments are available. Treatment helps extend the time a MD patient can remain mobile, improves heart and lung muscle strength, and can improve the quality and sometimes the length of life for MD patients.

Lifelong monitoring and assessment of walking, swallowing, breathing and hand function helps guide adjustments in treatment as the disease progresses. The care team should include a neurologist with expertise in neuromuscular diseases, a physical medicine and rehabilitation specialist, and physical and occupational therapists. It may also include a lung specialist (pulmonologist), heart specialist (cardiologist), sleep specialist, endocrine system specialist (endocrinologist), and orthopaedic surgeon.

Treatment options include:

  • Medications such as corticosteroids can slow disease progression and help with muscle strength
  • Medications for patients with certain types of Duchenne MD received FDA approval in 2016 and 2019
  • Heart medications (ACE inhibitors or beta blockers) can help if MD damages the heart
  • Physical and occupational therapy can strengthen and stretch muscles, maintaining function and range of motion
  • Using mobility aids, such as canes, walkers and wheelchairs, can increase mobility and independence
  • Speech therapy helps those with swallowing problems
  • Heart pacemaker can treat heart rhythm problems and heart failure
  • Braces can help keep muscles and tendons stretched and flexible to slow the progression of contractures, and support weak muscles to maintain mobility
  • Respirators and ventilators help patients breathe who develop lung issues; a sleep apnea device at night improves oxygen delivery
  • Feeding tube helps patients whose swallowing muscles are affected 
  • Surgery can relieve tension on contracted muscles, or correct scoliosis 
  • Exercise can be helpful: range-of-motion exercises keep joints flexible to maintain mobility, and low-impact aerobic exercise (walking or swimming) maintain strength, mobility, and general health
  • Self-care is important: prevent obesity by eating healthy and maintaining a healthy weight, quit smoking to protect heart and lungs, stay current with flu and pneumonia vaccines

References

Mayo Clinic. (2020, Jan). Muscular Dystrophy. Retrieved 2-1-22, {https://www.mayoclinic.org/diseases-conditions/muscular-dystrophy/symptoms-causes/syc-20375388#:~:text=Muscular%20dystrophy%20is%20a%20group,many%20kinds%20of%20muscular%20dystrophy.}
Mayo Clinic. (2020, Jan). Muscular Dystrophy Diagnosis and Treatment. Retrieved  2-1-22, {https://www.mayoclinic.org/diseases-conditions/muscular-dystrophy/diagnosis-treatment/drc-20375394}
Cleveland Clinic. (N.d.) Muscular Dystrophy. Retrieved 2-1-22, {https://my.clevelandclinic.org/health/diseases/14128-muscular-dystrophy}
Johns Hopkins. (N.d.) Types of Muscular Dystrophy and Neuromuscular Diseases. Retrieved 2-1-22, {https://www.hopkinsmedicine.org/health/conditions-and-diseases/types-of-muscular-dystrophy-and-neuromuscular-diseases]
Medline Plus. (2021, Oct). Neuromuscular Disorders. National Institute of Health. Retrieved 2-1-22, {https://medlineplus.gov/neuromusculardisorders.html}
Mayo Clinic. (2021, June) Neurology. Retrieved 2-1-22, {https://www.mayoclinic.org/departments-centers/neuromuscular-disease-group/overview/ovc-20443670}

Information

Medically reviewed by:

Dr. Desiree Levyim

Dr. Desiree Levyim is a board eligible neurologist in practice since 2020. She joins TeleMed2U in our mission to provide increased access to healthcare.

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