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Correlating EMG exercise tests with genotype International Conference on the Nondystrophic Myotonias

Correlating EMG exercise tests with genotype International Conference on the Nondystrophic Myotonias. Marianne Arzel-Hézode, Emmanuel Fournier Centre de référence des Canalopathies Musculaires Hôpital La Salpêtrière, Paris, France.

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Correlating EMG exercise tests with genotype International Conference on the Nondystrophic Myotonias

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  1. Correlating EMG exercise tests with genotypeInternational Conference on the Nondystrophic Myotonias Marianne Arzel-Hézode, Emmanuel Fournier Centre de référence des Canalopathies Musculaires Hôpital La Salpêtrière, Paris, France

  2. Muscle channelopathiesPatients with EMG and genetic diagnose : N=171(La Salpêtrière, 1996-2007) • Myotonic syndromes N = 104 • Myotonia CLCN1 (A313T, P480L…) 33 • Paramyotonia SCN4A (T1313M, R1448C/H/G, Q270K…) 40 • SCM («PAM ») SCN4A (G1306A/V, V445M, A715T, S804N…) 31 • Periodic paralysis N = 67 • HyperPP SCN4A (T704M, R675G, I693T…) 25 • HypoPP-1 CACNLA1 (R528H, R1239H) 24 • HypoPP-2 SCN4A (R672G/H, R1135H…) 6 • Andersen (ATS) KCNJ2 (C54F, T75M, C154F/Y, T309I…) 12

  3. Supramaximal Nerve stimulation MU2 MU1 CMAP Electrophysiological abnormalities triggered by pioneer tests • CMAP amplitude decreases were observed : • during 10 Hz repetitive nerve stimulation in myotonic syndromes • Lambert et al. 1952, Bastron 1960, Ricker et al. 1973, Brown 1974, Aminoff et al. 1977 • after a single short exercise test in myotonic syndromes • Streib et al. 1982, Streib 1987 • after a long exercise test in periodic paralyses • Mc Manis et al. 1986, Kuntzer et al. 2000 • Interpretation • CMAP amplitude correlates with the number of functional muscle fibers • Its decrease is an index of muscle weakness experienced after exercise • Exercise tests = provocative tests

  4. I Long exercise test Right hand (ulnar - ADM) Exercise lasting 5 minutes (respecting regular brief rests) Recording every 5 minutes during 40-45 minutes post-exercise rest II Repeated short exercise test Left hand (ulnar - ADM) 3 exercises of 10 seconds with 1 minute between each trial Recording every 10 seconds for 50 seconds after each exercise 1st EMG protocol (1996, revised 2000) Ann Neurol 2004 • PatientsN = 51 • Chlore Myotonia (MC) 6 • Paramyotonia (PC) 16 • Sodium Myotonia (SCM) 8 • Sodium HyperPP 6 • Sodium HypoPP-2 2 • Calcium HypoPP-1 13 • Control Subjects N = 41 • III • Search for myotonic discharges with needle EMG • Deltoid, extensor digitorum communis, 1st interosseus dorsalis, tibialis anterior

  5. 1st EMG protocol

  6. Repeated short exercise test Chloride Myotonia - 61 % - 45 % - 20 % « Warm-up » phenomenon Type II Post-exercise myotonic potentials (PEMP) Sodium Paramyotonia - 48 % - 64 % • Aggravation with exercise repetition • Stiffness-weakness continuum Type I

  7. Five main EMG patterns Fournier et al.Ann Neurol 2004

  8. I Repeated short exercise test Right hand (ulnar -ADM) 3 exercises of 10 s with 50 s rest intervals II Cooling test Left hand (ulnar -ADM) Ice bag for 7 minutes Repeated short exercise test at cold 3 exercises of 10 s with 50 s rest intervals 2nd EMG protocol for distinguishing myotonic syndromes (2003) Ann Neurol 2006 • PatientsN = 61 • Chlore Myotonia 18 • Paramyotonia (PC) 22 • Sodium Myotonia (SCM) 14 • DM1/DM2 7 • Control Subjects N = 31 • III • Search for myotonic discharges • Needle EMG of deltoid, EDC, 1st IOD, tibialis anterior Total exam lasts 20 minutes

  9. 2nd EMG protocol for distinguishing myotonic syndromes

  10. Worsening of the abnormalities observed at room temperature Pattern changes Improvement of EMG distinctions with cold - 82 % - 90 % - 93 %

  11. 80 % SCN4A 100 % SCN4A EMG guides toward myotonic syndrome genotypes 86 % 85 % 60 % 14 % 15 % 20 % 20 % Ann Neurol 2006

  12. EMG Protocols’ Objectives • Diagnosis • Disclose functional abnormalities by mimicking provocative circumstances • Explain symptoms (electrical response changes as index ) • Determine differential diagnosis of weakness episodes • And more : distinguish closer clinical phenotypes • Guide molecular diagnosis • Isolate physiopathological mechanisms • Look for therapeutical advances

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