Exercise and myasthenia gravis (MG)

by myasthenia.org

Treatment can be long and difficult for patients with myasthenia gravis (MG), a chronic disorder characterized by weakness of skeletal muscles and rapid fatigue with exercise. Typically, muscle weakness worsens throughout the day’s activities, and improves after periods of rest. Although the voluntary muscles are most commonly affected, muscles of speech, swallowing, chewing, facial expression, and breathing may be involved.

The ocular and eyelid muscles are often affected first, with weakness spreading to facial and swallowing muscles before entering the trunk and limb musculature over a period of months. Bodily weakness is usually symmetrical, with proximal more than distal muscles showing decreased strength. Despite muscular weakness, deep tendon reflexes are typically preserved.

Weak signals

This rare acquired autoimmune disorder is caused by an abnormality in the body’s response to acetylcholine, a compound that helps transmit nerve impulses. With MG, the body’s immune system produces antibodies that block or destroy many of the receptor sites for acetylcholine at the neuromuscular junction of skeletal muscles. With fewer receptor sites available, the muscles receive fewer nerve signals, resulting in weakness.

MG can present in individuals at any age, but it is more common in men older than 50 and women younger than 40. There is no cure, but the treatments available help control the signs and symptoms.

The autoimmune disorder is diagnosed by laboratory blood testing for anti-acetylcholine receptor antibodies; antistriational antibodies also are tested to examine the differences between antibody responses against cholinergic receptors in skeletal, cardiac, and smooth muscles. Electromyography may help confirm the diagnosis.

Medications to improve neuromuscular transmission or suppress dysfunctional antibodies can help restore strength, and plasma exchange (plasmapheresis) is useful during times of symptom flare. Corticosteroids may be used to suppress abnormal immune responses. Sometimes, the thymus gland is removed, which can induce remission in younger patients.

Potential triggers that exacerbate muscular weakness with MG include stress, infections, missed or excessive medication, surgery, and pregnancy. Patients with MG are sensitive to raised core and ambient temperatures caused by excessive exercise and hot weather. In extreme cases, a patient may experience a cholinergic crisis, which results in respiratory failure and the requirement for intubation and ventilation. When this occurs, muscles that control breathing weaken to the point that ventilation is inadequate, resulting in a life-threatening event.

More Info
• Myasthenia Gravis Foundation of America: www.myasthenia.org
Gentle strengthening

With the help of PTs, patients with MG can see
significant improvement in muscle weakness. The most important aspect of treatment is to help patients stay as active and strong as possible, while avoiding sustained physical exertion.

“With the appropriate medication and supervision of an MD, as well as lifestyle changes recommended by a physical therapist, patients living with MG can maintain active and healthy lives,” says Dierdra L. Ricks, BS, PT, senior neurology and neurosurgery therapist at the University of North Carolina Hospitals in Chapel Hill.

Therapists should assess the patient’s endurance and fatigability by recording the distance a patient moves within a certain time period during a three-minute walking test. The number of rest breaks needed is noted while monitoring vital signs such as heart rate and oxygen saturation, Ricks explains.

“In order to prevent overexertion, I recommend that patients alternate upper extremity and lower extremity exercises to ensure sufficient rest breaks and perform less repetitions with each activity,” she says.

PTs should provide information regarding the importance of physical activity to stay strong, with tips to maximize daily function without overexertion, avoid extreme heat, and exercise earlier in the day. Repetitive and sustained muscular exercise should be avoided, as this can provoke weakness. However, if localized postactivity weakness occurs, application of ice to the affected muscle can improve neuromuscular transmission and restore strength within minutes.

Patients with MG are encouraged to use assistive devices to reduce the risk of falls that correspond with decreased strength and stability and increased fatigue as the day progresses.

Teaching energy conservation to patients with MG includes planning daily activities to allow them to prioritize and eliminate unnecessary tasks.

“I like to encourage my MG patients to use an acronym I created, PACE, to remind them of tips to utilize in order to improve their daily function,” Ricks notes.

The PACE acronym stands for:
• Peak dosage, planning daily activities
• Adapting the home, adequate rest, assistive
equipment, asking for help
• Conserving energy, check-ups with doctor,
cool temperature
• Emotional stability, exercising in moderation,
eliminating unnecessary daily tasks.

Therapists can help patients gently strengthen postural muscles of the head and neck to facilitate safe swallowing, as muscle weakness can lead to dysphagia, which puts patients with MG at risk for aspiration pneumonia.

Above all, the goal should be maintaining a safe and healthy activity level that enables patients to enjoy a good quality of life, staying strong without overexertion.

• Myasthenia Gravis Foundation of America: www.myasthenia.org

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