Myotonic Dystrophy (DM)

Adult-Onset DM1/DM2 and Juvenile-Onset DM1

Medical management

This section addresses medical management of the many symptoms of adult-onset DM1 and DM2, as well as childhood-onset DM1. These three forms of DM share similar medical management strategies. Multidisciplinary surveillance and management of these and other issues is optimal. Recommendations regarding management are based more on consensus and clinical experience than on evidence from randomized controlled trials.

Anesthesia warning

An unusually high rate of complications and even deaths associated with general anesthesia given during surgery have been reported in people with DM1. This can occur even if DM is mild. In fact, mild cases can be particularly dangerous because the surgeon, anesthesiologist, and patient may be less likely to pay attention to DM-associated symptoms when planning surgery. Regional anesthesia may be appropriate for some procedures, and for some patients with DM1.

Surgery usually can be safely undertaken with careful monitoring of cardiac and respiratory functions before, during, and after the procedure. Be sure to tell the entire medical team, especially those responsible for anesthesia, that you or your family member has DM. If possible, have the anesthesiologist and the neurologist communicate long before the surgery.

Succinylcholine should be avoided as well because of its potential to cause diffuse muscle contraction.

Adverse reactions to anesthesia do not seem as serious in DM2. However, caution is advised.

Breathing and coughing muscle weakness

In DM1, breathing muscle weakness can be an important factor in the disease course. It does not seem common in DM2. Obstructive sleep apnea may coexist with a diminished breathing drive, especially in those at highest risk because of coexisting obesity.

A good way to treat respiratory muscle weakness is to pump air into the lungs during the night with a small, portable “breathing booster” known as a bilevel positive airway pressure device (BiPAP is the trademarked name of the device made by Philips Respironics). It is usually used with a face mask that can be easily put on and taken off. This kind of breathing assistance also can be used during the day, although usually that is not necessary.

Devices that use continuous positive airway pressure — called CPAP — often are not appropriate for people whose respiratory problems are caused by weak breathing muscles. For more, see Not Enough ZZZzzzs.

Cough assistance machines and assisted cough techniques can help people clear out secretions, especially when a person with DM1 has a cold or chest infection. An MDA Care Center physician, respiratory therapist, or pulmonologist can advise about these techniques and machines and how to use them.

Cataracts

Cataracts, opaque spots on the lens of the eye, are common in both DM1 and DM2. If they interfere with daily living activities, they can be removed surgically. Caution with anesthesia and pain medication is necessary, and the surgical team should be aware of and familiar with a patient's DM. Surveillance for cataracts is recommended for those with mild DM1 disease.

Cognitive and behavioral abnormalities

Cognitive and behavioral abnormalities can exist at any point in DM1 or DM2, although they are more common in DM1 and particularly when DM1 begins in childhood. In general, these abnormalities manifest as an "avoidant" or apathetic personality, intellectual impairment with low IQ, attentional deficits, executive dysfunction, anxiety, and mood disorders. An evaluation by a neuropsychologist, special education strategies, and counseling can be helpful, as can medications that increase alertness and attention (for example, modafinil), depending on the person and the details of his or her individual situation.

Daytime sleepiness

Daytime sleepiness, which is more common in DM1 but also occurs in DM2, can sometimes be helped with medication. Methylphenidate (Ritalin) and modafinil (Provigil) were proved to be beneficial and well tolerated in treating excessive daytime sleepiness.

Another approach that can be tried is to coax the body into a better rhythm of sleeping and waking by going to bed and getting up at the same time every day. Consult with a respiratory specialist familiar with muscular dystrophy to determine if breathing is compromised during sleep.

The daytime sleepiness of DM1 may be aggravated by breathing issues. Thus, it is critical to assess the quality of sleep in patients with DM1, probing for whether there are unexplained awakenings, nocturnal restlessness, and/or loud snoring punctuated by occasional awakening and gasping for breath, all of which should suggest the presence of a sleep-related respiratory disorder and lead to further study.

Gastrointestinal dysfunction

Dysfunction of the throat or esophageal muscles can occur in DM1, impairing swallowing. It is important to watch for swallowing problems, such as a tendency to choke on food or drinks, and be sure to mention them to a doctor. A swallowing specialist can help people learn to swallow more safely and, if necessary, how to change the consistencies of foods and liquids so they can be swallowed more easily. Referral to a nutritionist may be useful for advice regarding calorie supplementation.

Vomiting can be very dangerous for a person with DM whose swallowing muscles are weak. A head-down position is crucial to prevent inhaling the vomit (a possibly fatal event). Read Sorting Out Speech Services for more information about speech and swallowing specialists.

In DM, the intestines may not move digested food along as well as they should, so constipation can be a chronic problem. A doctor can help set up a more effective bowel schedule and, if necessary, recommend laxatives, suppositories, or enemas to help manage this condition.

The gallbladder, a hollow sac on the right side of the upper abdomen, likewise can be sluggish in DM1, leading to the formation of gallstones. These may cause persistent pain in the upper abdomen. Surgery to remove the gallbladder can be performed if necessary.

Gallbladder dysfunction does not seem to be a feature of DM2.

Cardiac abnormalities

Not everyone with DM needs treatment for heart problems, but everyone should be checked for heart health on a regular basis. Complications seem more common in DM1 than in DM2, although both types of DM can affect the heart. 2017 guidelines from the American Heart Association recommend carefully oversight of one’s cardiac history, seeking evidence for palpitations, blackouts, and shortness of breath. An echocardiograph, electrocardiograph, and ambulatory ECG monitoring should be done at the time of DM diagnosis, regardless of symptoms.

The most common type of heart problem in DM is an abnormal heart rhythm (arrhythmia) called a conduction disturbance. When a conduction disturbance is present, signals do not move through the heart in the normal way. This can be very serious, even causing sudden death. Therefore, it is imperative that people with DM have regular electrocardiograms (EKGs, aka ECGs).¹

DM patients can also develop an abnormal heart rhythm known as atrial fibrillation, in which the top part of the heart beats extremely fast, causing turbulent blood flow that can lead to clots and strokes.

Various electronic devices (pacemakers and implantable defibrillators) can be used to treat abnormal heart rhythms. Sometimes, medications also are prescribed. These include such drugs as beta blockers and anti-arrhythmic drugs.

Sometimes, especially late in the DM disease course, the heart muscle itself can weaken, causing a type of disorder known as cardiomyopathy. Medications can be prescribed to lessen the stress on the heart in this disorder.

For more information, read Cardiac Care in DM: Lack of Symptoms May Mask Deadly Problems and Revising Cardiac Care in Muscular Dystrophies.

Insulin resistance

A phenomenon known as insulin resistance (meaning the insulin produced by the body is not utilized as well as it should be) can cause high blood sugar and sometimes even diabetes. Insulin resistance is common in people with DM1 and is thought to affect approximately 20% of those with DM2. The phenomenon often does not cause any trouble but should be monitored by a physician. If it does become problematic, insulin or other medications that lower blood sugar can be prescribed.

Myotonia

Myotonia (the inability to relax muscles at will) occurs in both DM1 and DM2. Grip myotonia — not being able to release one's grip after, for example, shaking hands or holding a steering wheel — can be the main thing people notice. If myotonia is bothersome, it can be treated by drugs such as mexiletine. Because of the rare proarrhythmic effects of mexiletine in those with underlying heart arrhythmias, it is best to obtain a cardiology consultation before beginning therapy with mexiletine, particularly for patients with DM1 who have current or remote cardiac symptoms or for those with an abnormal baseline electrocardiogram.²

Other drugs including phenytoin, procainamide, propafenone, flecainide, and carbamazepine have been evaluated as potential treatment for myotonia, However, there is not enough information yet from clinical studies to determine a standard of care.

Pain

Pain in the skeletal muscles is a common feature of DM. Pain for patients with DM2 may be induced by exercise, palpation, and temperature changes.^{3, 4, 5, 6}

A doctor may suggest an over-the-counter pain remedy or even a prescription pain medication in some circumstances. Drugs that may be effective for this problem include nonsteroidal anti-inflammatory drugs, gabapentin, tricyclic antidepressants, mexiletine, and low-dose glucocorticoids, such as oral prednisone. Some people find warm baths, heating pads, or massage to be helpful.

A doctor should always be told that DM is present, as this may make a difference in how the pain should be treated. (For instance, in DM1, it is important to avoid pain medications that affect breathing).

Pregnancy and childbirth

In both DM1 and DM2, pregnancy can be complicated, requiring special care and attention, particularly during labor.

In DM1, uterine and vaginal muscles may be weak, posing additional problems for pregnancy and delivery and making a surgical delivery more likely. Reactions to anesthesia and pain medications can be unpredictable and need the attention of someone familiar with these disorders.

In addition, a mother who has mild DM1 may give birth to a child with congenital-onset DM1 who will need a neonatal intensive care unit and specialists familiar with this condition.

For more information on myotonic dystrophy and pregnancy, read Caution, Preparation and Teamwork Lead to the Best Pregnancy Outcomes in Women with Neuromuscular Diseases. Also be sure to read Baby Born with Challenges in the same series.

Skeletal muscle weakness

In DM1, weakness of the skeletal muscles is concentrated in the face, tongue, neck, forearms, hands, and feet, especially at the beginning. Upon disease progression, other muscles can be affected, such as thigh and respiratory muscles.

Some people can compensate for weak foot muscles by picking up the foot from the knee and walking with a “marching” step. Eventually, though, many people with DM1 find that a cane or walker is helpful to compensate for foot and leg weakness.

A lower leg brace called an ankle-foot orthosis, or AFO, may be needed. Some people with DM1 use a wheelchair or a power scooter for convenience when covering long distances. For more, read Putting Your Best Foot Forward.

Various devices that hold the hand in a good position for using a keyboard or writing or drawing can help compensate for weak wrist and hand muscles. Eye lid crutches or blepharoplasty may be helpful for troublesome ptosis (drooping or falling of the upper eyelid) encountered in DM1.

There is no clear evidence of benefit or harm of moderate-intensity strength training for DM1. Therefore, patients with DM are recommended to engage in low-intensity exercise, to the extent that they are capable and without undue physical stress. It is also suggested that exercise include gentle stretching actions at selected joints. Cardiology consultation is recommended in patients with DM1 or DM2 prior to beginning an exercise program, especially those with cardiac symptoms.

In DM2, skeletal muscle weakness begins in the large muscles close to the center of the body (proximal muscle weakness). Early in the disease course, there is weakness of the hips and thighs. The upper arms and shoulders are often involved early, and the forearms and fingers can be affected early as well.

The facial muscles typically remain strong, weakening in only a small percentage of people with DM2. The lower legs and feet tend to remain strong as well, although the calf muscles can become enlarged.

Walking aids, such as walkers and canes, or scooters or wheelchairs can be helpful.

References

1. Lund, M. et al. Cardiac involvement in myotonic dystrophy: A nationwide cohort study. Eur. Heart J. (2014). doi:10.1093/eurheartj/ehu157
2. Logigian, E. L. et al. Mexiletine is an effective antimyotonia treatment in myotonic dystrophy type 1. Neurology (2010). doi:10.1212/WNL.0b013e3181dc1a3a
3. Meola, G. & Moxley, R. T. Myotonic dystrophy type 2 and related myotonic disorders. Journal of Neurology (2004). doi:10.1007/s00415-004-0590-1
4. Suokas, K. I., Haanpää, M., Kautiainen, H., Udd, B. & Hietaharju, A. J. Pain in patients with myotonic dystrophy type 2: A postal survey in Finland. Muscle and Nerve (2012). doi:10.1002/mus.22249
5. George, A., Schneider-Gold, C., Zier, S., Reiners, K. & Sommer, C. Musculoskeletal pain in patients with myotonic dystrophy type 2. Arch. Neurol. (2004). doi:10.1001/archneur.61.12.1938
6. Udd, B. & Krahe, R. The myotonic dystrophies: Molecular, clinical, and therapeutic challenges. The Lancet Neurology (2012). doi:10.1016/S1474-4422(12)70204-1
7. Reardon, W., Newcombe, R., Fenton, I., Sibert, J. & Harper, P. S. The natural history of congenital myotonic dystrophy: Mortality and long term clinical aspects. Arch. Dis. Child. (1993). doi:10.1136/adc.68.2.177