Management of Adult-Onset Myotonic Dystrophy DM1

Muscle

Weakness in distal muscle (including hands, arms and feet) can interfere with gait and mobility. Muscle strength and flexibility may be preserved to some extent with rehabilitation therapy or physical therapy. Assistive devices (such as neck braces, arm and foot braces, canes, walkers, scooters, and wheelchairs) may be required to ensure comfort and safe navigation, particularly when traveling longer distances.

In cases where moderate to severe myotonia interferes with mobility and activity, an antimyotonic drug such as mexiletine, may be administered.

Exercise recommendations vary between individuals. In general, moderate exercise and gentle stretching may be beneficial, particularly for contracture symptoms. However, since exercise can trigger heartbeat irregularities, new exercise programs should not be initiated without supervision. Particularly with young patients and those with cardiac symptoms, electrocardiographic monitoring may be recommended until the consequences of any new program are determined.

Heart

A careful cardiac history (seeking evidence for palpitations, blackouts, syncope, and dyspnea) and  examination (ascertainment for bradyarrhythmia, ectopic beats, mitral valve prolapse, and atrial fibrillation) are recommended. Cardiomyopathy (damage to the heart that can impair its ability to pump blood effectively) can appear starting in the second decade of life. These issues can be serious and life-threatening, even in asymptomatic individuals. As a result, yearly electrocardiograms (EKGs) are recommended, as well as echocardiograms if cardiomyopathy is suspected.  24-hour ambulatory EKG monitoring should be performed when arrhythmias are suspected clinically but are not detected on standard EKG.  Special attention should be paid to ventricular tachycardia, an arrhythmia which is life-threatening and caused by cardiomyopathy.

When cardiac issues are present, devices that detect and regulate heart rhythm (such as a pacemaker or implantable cardioverter defibrillator [ICD]) may be surgically inserted. These devices have been shown to be life-saving in adults where severe abnormalities were demonstrated using electrophysiological (EP) studies; however, debate exists as to who should receive EP assessment and whether a combined pacemaker/ICD device should be used instead of a pacemaker alone for certain patients.

Breathing

Because many patients experience chronic chest infections or respiratory insufficiency, regular assessment of lung function is essential when the patient has respiratory symptoms. Full respiratory assessment can include:

  • clinical observations (including patient comfort level, respiratory rate, breathing sounds, and pulse oximetry to measure oxygen levels in the blood)
  • checking for pneumonia and diaphragm weakness
  • swallowing assessment to evaluate aspiration (the accidental inhalation of food and drink particles)
  • respiratory function testing (such as  forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) tests that measure the amount of air a patient can forcibly blow out)

Aids such as incentive spirometry and cough assist devices may be useful for patients who are unable to breathe well enough to provide sufficient oxygen and remove sufficient carbon dioxide from their bodies. These devices exercise breathing muscles and help maximize lung capacity.

Vision

Because of DM1 patients' predisposition to cataracts and retinal damage, even in younger years, eye examinations are typically recommended at least every two years. If cataracts are present, they can be successfully treated with surgery.

Ptosis (droopy eyelids) may be treated with eyelid crutches attached to eye glasses. In the most severe cases where vision is blocked by the eyelids, surgery (blepharoplasty) may be used. Surgery only provides temporary improvement as the cause of ptosis has not been addressed and the symptoms typically return. However, the implantation of slings (into the eyelids) that are attached subcutaneously to a muscle in the forehead, creates the possibility for an ophthalmologist to adjust the eyelids as they continue to weaken and droop. 

Nutrition and digestive system

Nutritional and swallowing assessments are often part of regular monitoring of patients with myotonic dystrophy DM1. Dysphagia (difficulties eating and swallowing) can lead to chronic lung complications, poor nutrition, and fatigue. While no direct treatment is typically provided, practices to reduce the symptoms may be recommended (e.g., eating smaller, more frequent meals, thickening of food consistency, elevation of the head of the bed, avoidance of cold fluids, and caloric supplementation).

Recurrent abdominal pain and bloating may be present, as can irritable bowel syndrome. In such cases, symptomatic treatment is available with medications that target constipation or diarrhea. Preventative measures, including a high fiber diet, are often recommended for constipation.  Reduced intake of leafy vegetables and decreased fiber may be recommended for diarrhea. Severe abdominal pain may result from paralysis of the intestine.  In rare cases, enlargement of the colon (megacolon) may occur.  These severe intestinal complications need medical care by a gastro-intestinal specialist.

Cognitive Impairment

Cognitive skill testing and neuroimaging may be done to evaluate mental function. Visual-spatial ability, executive function, and visual memory, in particular, may be assessed in myotonic dystrophy DM1 patients. Treatment options are limited and depend on the nature of any impairment seen.

Both symptomatic treatment and preventative approaches are taken to improve quality of life for individuals who experience excessive daytime sleepiness (EDS). When sleep apnea is considered to be contributing to the fatigue, use of a nasal continuous positive airway pressure (N-CPAP) can improve sleep. Stimulant medications (such as modafinil) can also mitigate EDS symptoms.

Endocrine issues

Endocrine issues may be treated by hormone replacement therapy.

Because diabetes occurs in a small number of myotonic dystrophy patients, annual measurement of fasting serum glucose concentration and glycosylated hemoglobin concentration is often done. Antidiabetic drugs (such as metformin) may be used to normalize blood sugar levels and address mild diabetic symptoms.

Anesthesia

The neuromuscular, cardiac, and respiratory symptoms of myotonic dystrophy DM1 result in elevated risk of complications associated with the use of anesthesia. Certain drugs used in surgery suppress respiratory function, cause severe myotonic reactions, and exacerbate cardiac arrhythmias. Post operative pulmonary complications are also common. As a result, careful monitoring of cardiac and respiratory function is essential before, during and after the use of anesthesia.

Anesthesiologists MUST be notified about a diagnosis of myotonic dystrophy DM1. Please see Anesthesia Guidelines for further information.

Other

Pilomatrixoma (benign tumors under skin associated with hair follicles) can be removed as needed.

Multiple options are available for individuals with myotonic dystrophy who are pregnant, including prenatal testing and special monitoring during pregnancy. Because mothers with myotonic dystrophy DM1 have an elevated risk of having a child with the congenital form, planning for immediate intensive neonatal care prior to delivery is also warranted. Please see Family Planning for more information.

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More technical information on the symptoms, diagnosis and management of Adult-Onset Myotonic Dystrophy DM1 can be found by clicking here.