Congenital myotonic dystrophy
Congenital myotonic dystrophy is the early childhood form of myotonic dystrophy (also known as Steinert's disease).Usually in myotonic dystrophy the symptoms begin to show in childhood or later in life, but symptoms of congenital myotonic dystrophy are evident from birth. It occurs only when the mother already has myotonic dystrophy (although she may not be aware of this) and she passes it on to the child in a more severe form.Congenital means 'from birth' because the condition is usually identified at birth or soon after;myotonic means 'involving muscle stiffness'; and dystrophy is 'muscle wasting and weakness'. (Congenital myotonic dystrophy is not the same as congenital myopathy or congenital muscular dystrophy. For more information about these or other conditions please contact the Muscular Dystrophy Association).
- Poor fetal movement
- Infant hypotonia
- Respiratory difficulty
- Feeding difficulty
- Generalized weakness
- Jaw hangs open
- Carp-like mouth
- Mental retardation
- Impaired motor function
- Fecal incontinence
- Irregular bowel habit
Diagnosis of DM is not difficult once the disease is considered. However, the true problem may be masked because symptoms can begin at any age, can be mild or severe, and can occur with a wide variety of associated complaints. Diagnosis of DM begins with a careful medical history and a thorough physical exam to determine the distribution of symptoms and to rule out other causes. A family history of DM or unexplained weakness helps to establish the diagnosis.
Prognosis of Congenital myotonic dystrophy: poor - 25% die within 18 months, 50% survive to mid-30's
There is currently no cure for or treatment specific to congenital myotonic dystrophy. Therefore, the focus is on managing the complications of the disease, particularly those relating to the cardiopulmonary system as these account for 70% of deaths due to DM1. Pacemaker insertion may be required for individuals with cardiac conduction abnormalities. Central sleep apnoea or obstructive sleep apnoea may cause excessive daytime sleepiness, and these individuals should undergo a sleep study. Non-invasive ventilation may be offered if there is an abnormality. Otherwise, there is evidence for the use of modafinil as a central nervous system stimulant, although a Cochrane review has described the evidence thus far as inconclusive.
Some small studies have suggested that imipramine, clomipramine and taurine may be useful in the treatment of myotonia. However, due to the weak evidence and potential side effects such as cardiac arrhythmias, these treatments are rarely used. A recent study in December 2015 showed that a common FDA approved antibiotic, Erythromycin reduced myotonia in mice. Human studies are planned for erythromycin. Erythromycin has been used successfully in patients with gastric issues.
Altered splicing of the muscle-specific chloride channel 1 (ClC-1) has been shown to cause the myotonic phenotype of DM1 and is reversible in mouse models using Morpholino antisense to modify splicing of ClC-1 mRNA.
Combined strengthening and aerobic training at moderate intensity was deemed safe for individuals with neuromuscular diseases and the combination was found to increase muscle strength. Specifically, aerobic exercise via stationary bicycle with an ergometer was found to be safe and effective in improving fitness in people with DM1. The strength training or aerobic exercise may promote muscle and cardiorespiratory function, while preventing further disuse atrophy. Cardiovascular impairments and myotonic sensitivities to exercise and temperature necessitate close monitoring of people and educating people in self-monitoring during exercise via the Borg scale, heart rate monitors, and other physical exertion measurements.
Muscular weakness of dorsiflexors (dorsiflexion) hinders the ability to clear the floor during the swing phase of gait and people may adopt a steppage gait pattern or ankle-foot-orthotics may be indicated. Factors such as hand function, skin integrity, and comfort must be assessed prior to prescription. Neck braces can also be prescribed for neck muscle weakness.
obility aids and adaptive equipement
Upper and lower limb weakness, visual impairments and myotonia may lead to the need for mobility aids and functional adaptive equipment such as buttonhooks and handled sponges for optimal hand function. If assistive devices and home adaptations are needed, physical therapists may refer on to occupational therapist(s) for further assessment.