| Fact | Explanation |
|---|---|
| Difficulty in relaxing hand grasp | Slow relaxation of muscles after contraction. [1,2] |
| Visual impairment | Development of cataract due to same genetic defect as that causing muscle atrophy and myotonia. [1,2,3] |
| Difficulty in swallowing | Weakness of muscles in pharynx. [1,2] |
| Loss of weight | Due to muscle wasting. [2,4] |
| Impotence | Due to hypogonadism with low testosterone levels. [5] |
| Baldness | Same genetic defect on chromosome 19 causes baldness. [1,2] |
| Weakness in limbs | Due to muscle wasting. [2] |
| Sudden falling like a log while walking | Myotonia causing sudden inability to maintain balance. [1,2] |
| Fact | Explanation |
|---|---|
| Tapping the thenar eminence of hand causes a dimple which persists for a while | Failure of immediate muscle relaxation after contraction has ceased. [1,2] |
| Ptosis | Weakness of levator palpebrae superioris muscle. [1,2] |
| Atrophy of testicles | Primary gonadal failure with high serum FSH and LH hormone levels and low testosterone levels. [4] |
| Atrophy of face and neck muscles | Muscle atrophy due to triplet expansion in chromosome 19. [3] |
| Tapping the lateral border of tongue causes a deep dimple at the site of impact which persists for a while | Due to persistent muscle contraction without immediate relaxation . [1,2] |
| Tachycardia or bradycardia or irregular pulse | Due to fibrosis and fatty infiltration of conducting system and AV node. [1,2] |
| Fact | Explanation |
|---|---|
| Myotonia congenita | Presents with generalized myotonia and stiffness. Muscles are prominent and there are no extra muscular abnormalities. [1] |
| Recessive generalized myotonia | Presents at the age of 4 to 12 years with symptoms of myotonia mainly in legs. Muscle hypertrophy is common. [1] |
| Paramyotonia congenita | Characterized by muscle stiffness that is triggered or worsened by cold weather. Repeated muscle contractions lead to flaccid paralysis. [1] |
| Hyperkalemic periodic paralysis with myotonia | Presents with stiffness and paralysis. Can be triggered by rest following exercise, cold and hunger. [1] |
| Fact | Explanation |
|---|---|
| Electromyography | This shows a combination of myotonic discharges and myopathic appearing motor units. Characteristic bursts of repetitive potentials which vary both in potential and frequency are called "dive bomber" potentials. [1] |
| Serum creatinine level | May be mildly elevated. [1] |
| Muscle biopsy | This is histologically grossly abnormal in clinically affected patients. Features include fibrosis, variability in fiber size, sarcoplasmic masses etc. [1] |
| Genetic testing (Polymerase chain reaction and southern blotting) | This is the mainstay of diagnosis. It shows the CTG trinucleotide repeat expansion in gene which codes for a myosine kinase expressed in skeletal muscle. [1] |
| Fact | Explanation |
|---|---|
| ECG | Should be done yearly to detect cardiac arrhythmia. [1] |
| Sleep study | For any symptoms of excessive daytime sleepiness and obstructive sleep apnoea. [1] |
| Fasting blood sugar | There is no significant increase in incidence of diabetes mellitus among patients with Dystrophia Myotonica compared to the general population. However there is evidence of insulin resistance due to abnormal splicing of the insulin receptor mRNA to a more insulin insensitive isoform. Therefore any clinical suspicion of diabetes mellitus should prompt a fasting blood sugar test. [2] |
| Fact | Explanation |
|---|---|
| Prenatal molecular diagnosis | This can be done using retrieved transcervical trophoblastic cells or maternal plasma. [1] |
| Fact | Explanation |
|---|---|
| Dehydroepiandrosterone (DHEA) | Initial pilot studies suggested improvement of muscle power. But a recent multicentre, randomised, double-blind. placebo controlled study did not substantiate this. [1] |
| Exercise training | This can maximize muscle and cardio respiratory function and prevent disuse atrophy of muscles. [2,3] |
| Sodium channel blockers | Myotonia is the main cause of disability in patients with dystrophia myotonica.Myotonia could be caused by inactivation defect of Sodium channels causing long-lasting depolarisation of the muscle fiber. Thus blocking these channels can relieve myotonia. [3] |
| Benzodiazepines: Diazepam | Probably due to membrane stabilizing effect. [4] |
| Calcium antagonists: Nifedipine | High concentrations of Calcium have been found in red blood cells and skeletal muscle in myotonic dystrophy. Thus by blocking calcium channels myotonia gets relieved. [9] |
| CNS stimulant drugs | Modafinil 200-400 mg/day - The mechanism of action of modafinil is still not completely understood, but it is associated with an activation of the tuberomamillary nucleus and orexin-containing neurons. Methylphenidate and Dexamphetamine: these drugs are useful in the sleep disordered. breathing. [5] |
| Dietary manipulation | Thickening food, adding supplements and adopting safer swallowing techniques help to overcome dysphagia. [6] |
| Tricyclic anti depressive drugs: Imipramine, Clomipramine | It has been hypothesized that myotonic dystrophy is caused by a generalized disorder of membrane aminergic and petidergic receptors. Thus Inhibition of re uptake of neurotransmitters can benefit myotonia. [7,8] |
| Fact | Explanation |
|---|---|
| Gene therapy | This is the only mode of definitive treatment. However this option is still at in vitro experimental level. [1,2] |