1. Myopathies and their Electrodiagnosis3 Randall L. Braddom, M.D., M.S. Clinical Professor Robert Wood Johnson Medical School and the New Jersey Medical School rlbraddom@comcast.net

2. The Five Steps of EMG  First published by Johnson and Melvin in 1971. Johnson EW, Melvin JL. Value of electromyography in lumbar radiculopathy. Arch Phys Med Rehabil (June) 1971. 52: 239-243

3. COLLAGEN-VASCULAR MYOPATHIES  Dermatomyositis  Polymyositis  Scleromyositis  Rheumatoid myositis

4. DERMATOMYOSITIS  Bimodal distribution  Weakness, skin rash, malaise  Weight loss, fever  Eyelid rash  Skin calcifications  Telangiectasia  Malignancy association in adults

10. POLYMYOSITIS  Weakness  No skin lesions  Associated with malignancy  May have dysphagia  Weight loss

11. INFECTIOUS MYOSITIS  Trichinosis  Cysticercosis (Taenia solium)  Viral

12. ENDOCRINE MYOPATHIES  Hyperthyroid  Hypothyroid  Cushings Disease/Steroids  Hypoparathyroid  Hyperparathyroid

13. CONGENITAL MYOPATHIES  Central Core  Myotubular  Nemaline Rod  Fiber Type Dysproportion  Mitochondrial

14. Conditions Having Both Clinical and EMG Myotonia  Myotonic Dystrophy MD1 MD2 (proximal myotonic myopathy)  Myotonia Congenita  Schwartz-Jampel Syndrome

15. Myotonic potentials (from Dumitru)

16. MD 1 (Classic Myotonic Dystrophy)  Cranial muscle wasting/weakness  Distal weakness more than proximal  Hatchet” face  Dysphagia, Dysarthria  First degree heart block/bundle branch block/ arythmias  Cataracts  Frontal baldness  Genetics: Autosomal dominant CTG Repeat Disorder

19. CLINICAL MYOTONIA  Sustained contraction of muscle caused by spontaneous repetitive depolarization of the muscle membrane  Arises from the muscle membrane...denervation does not stop it  Painless  Diminishes with exercise (warm-up phenomenon)  Worsened by cold  Action or percussion myotonia

20. Clinical Tests of Myotonia  Percussion: the “Myotonic Phenomenon”  Shake hands test Repeatedly shake hands  Delayed release of the hand that gets better on repetition  Close and open eyes test Repeatedly close eyes tightly  Lag in opening the eyes that improves with repetition

21. Percussion Myotonia (Pourmand)

22. MD 2 Proximal Myotonic Dystrophy  Findings same as MD 1 except: Different type of CTG expansion Weakness is proximal rather than distal More frequent insulin resistance Later (Adult) onset No congenital type of MD 2

23. ELECTRICAL MYOTONIA  Increases after rest  Two types of potentials resembling fibrillations positive wave  Wax and wane in frequency and amplitude  20-80 Hertz  Decremental response to high frequency stim

24. Exercise Testing for Myotonia  10-30 seconds of exercise causes decrement in CMAP in MD1 (not MD2)  5 minutes of exercise Paramyotonia congenita has rapid decrease in CMAP with slow recovery over 60 minutes In Periodic Paralysis the CMAP increases, then declines slowly over 30 minutes

25. Cooling Test for Myotonia  Cooling at 15 C for 15 minutes CMAP in paramyotonia congenita drops 75% Triggers weakness

26. Myotonic Dystrophy Genetics  The gene defect is an “expansion”  Consequently, it is usually much worse if inherited from the mother  Inheritance from the mother can give “Congenital Myotonic Dystrophy” A severe case in an infant can even be fatal

29. CLINICAL PARAMYOTONIA WITH EMG MYOTONIA  Paramyotonia Congenita  Hyperkalemic Periodic Paralysis Both give periodic attacks of weakness Both are sodium channelopathies  Hypokalemic Periodic Paralysis does not show paramyotonia clinically or myotonia on EMG

30. Muscle Sodium Channelopathies  Many undoubtedly exist  Common one is gene SCN4A chromosome 17q23,1-25.3  This produces PAM (Potassium aggravated myotonia) Paramyotonia congenita (PMC) Hyperkalemic periodic paralysis (HPP)

31. Muscle Sodium Channelopathies  The defect is in the fast inactivation of the sodium channel after depolarization occurs  Rate of activation is slowed, or channel opens to soon, or channel bursts when used a lot in a short time, or inactivation process is uncoupled from voltage dependence  End result is that there is too much intracellular sodium, causing spontaneous depolarizations in a progressive cascade effect  Only 2% of mutant channels need to be present in a muscle membrane to cause this

32. Muscle Chloride Channelopathies  Chloride channel gene CLCNa chromosome 7q35 Thomsen’s myotonia congenita (autosomal dominant) OR Becker’s myotonia congenita (autosomal recessive)  Mechanism for myotonic dystrophy is yet unknown

33. ELECTRICAL MYOTONIA WITHOUT CLINICAL MYOTONIA  Acid Maltase Deficiency Glycogenosis Type II  Glycogen storage disease Slowly progressive truncal and proximal limb weakness Death usually due to respiratory muscle weakness EMG shows myotonic discharges, fibs, positive waves, CRDs, and small MUAP. Heart and liver NOT enlarged Elevated CK

34. Myotonic Dystrophy Factoid  The weakness and the myotonia tend to be worse in distal muscles, especially the hands and the feet

35. EMG DISEASE  Wiechers and Johnson 1979 Patients with positive waves in every muscle No symptoms Thought it might be “form fruste” of myotonic dystrophy

36. EMG DISEASE  Mitchell and Bertorini 2007 (Arch Phys Med Rehabil 88:1212- 1213) 2 patients with EMG disease found to have CLCN1 gene abnormal  But no repeat expansions  One patient had elevated CK and one had minimal myotonic phenomenon  Speculate that this is very mild version of Myotonic Dystrophy

37. SELECTIVE MUSCLE FIBER ATROPHY  Type 1 Myotonic dystrophy Centronuclear myopathy Type 2 Corticosteroids Hyperthyroidism Disuse atrophy Cachexia Central nervous system disease

38. www.neuro.wustl.edu/neuromuscular  Best internet site for neuromuscular diseases, including myopathies  Kept up to date  Dx, Rx, Pathology, Genetics, etc.