Muscle - DM2


  • Skeletal muscle weakness and myalgia are major features of DM2.

  • The weakness is bilateral and progresses at the relatively slow rate of 1 to 3 percent per year. Involvement of distal and facial muscles is usually absent. Initial weakness is in proximal hip girdle and neck (flexors > extensors) muscles. Axial muscle weakness is frequent in DM2 and may result in lower back pain.

  • Myotonia – sustained muscle contraction and difficulty relaxing muscles may be absent. Even if it is not the most disabling aspect of the disease, myotonia can contribute to muscle stiffness, pain, prolonged hand grip, speech and swallowing difficulties, and GI issues, and may be associated with hand tremor.


  • Myalgic pains, which can be the most prominent clinical feature in the early stages and may severely affect occupational performance.

  • Neck flexor weakness, causing difficulty raising the head from a surface.

  • Impacts to employment and activities of daily living due to proximal and axial muscle weakness (e.g. climbing stairs, standing up from the floor, etc.).

  • Difficulty with myalgia, mobility, balance and falls.

  • Need for assistive devices or modifications in the home, school or workplace.


  • Discuss the following tests with your doctor:

    • Needle electromyogram (EMG) in proximal muscles.


  • Moderate- or low-intensity aerobic and resistance exercise minimizing sedentary activities, if possible.

  • Obtain a cardiac evaluation prior to starting a new exercise routine.

  • Orthoses, braces.

  • Walking aids such as a walking cane or walker.

  • Home modifications as necessary.

  • Evaluate annually through the primary care provider or by appropriate specialists, including physical therapists/physiotherapists, occupational therapists, speech/language pathologists, dietitians/nutritionists, social workers, nurses/nurse practitioners, physiatrists and orthopedists.

  • Mexiletine as an option for myotonia, if myotonia is present and is distressing. As mexiletine is an antiarrhythmic, obtain a electrocardiogram (ECG) prior to use.

  • Drugs affecting ion channels can improve myotonia, although their potential for causing cardiac arrhythmias must be weighed against their possible benefits.