Management of Proximal Myotonic Myopathy DM2

Muscle   

Weakness in proximal muscle can interfere with normal activity.  Assistive devices (such as neck braces) may provide relief of some complications.

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

Exercise recommendations vary between individuals. In general, low intensity exercise and gentle stretching may be beneficial. However, since exercise can trigger heartbeat irregularities, new exercise programs should not be initiated without supervision.

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 very important. Cardiomyopathy (damage to the heart that can decrease 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 people where severe abnormalities were demonstrated with electrophysical (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.

Vision

Because DM patients are predisposed 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.  

Cognitive Impairment

Cognitive skill testing and neuroimaging may be done to evaluate executive mental function. Treatment options are limited and depend on the nature of any impairment seen. 

Endocrine issues

Endocrine issues may be treated by hormone replacement therapy (hormone replacement therapy for males with hypogonadism).

Because diabetes occurs in a small number of DM 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 DM2 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 Proximal Myotonic Myopathy: DM2.  Please see Anesthesia Guidelines for further information.

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More technical information on the symptoms, diagnosis and management of Proximal Myotonic Myopathy: DM2 can be found by clicking here.