1. 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

2. Muscle channelopathies Patients with EMG and genetic diagnose :
Muscle channelopathies Patients with EMG and genetic diagnose : N=171 (La Salpêtrière, )
Myotonic syndromes N = 104
Myotonia CLCN1 (A313T, P480L…)
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)
HypoPP-2 SCN4A (R672G/H, R1135H…)
Andersen (ATS) KCNJ2 (C54F, T75M, C154F/Y, T309I…) 12

3. 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
MU1
MU2
Supramaximal
Nerve stimulation
CMAP
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. 1st EMG protocol (1996, revised 2000)
Long exercise test
Right hand (ulnar - ADM)
Exercise lasting 5 minutes (respecting regular brief rests)
Recording every 5 minutes during 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
Ann Neurol 2004
Patients N = 51
Chlore Myotonia (MC) 6
Paramyotonia (PC) 16
Sodium Myotonia (SCM) 8
Sodium HyperPP
Sodium HypoPP
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. for distinguishing myotonic syndromes (2003)
2nd EMG protocol
for distinguishing myotonic syndromes (2003) 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
Ann Neurol 2006
Patients N = 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. Improvement of EMG distinctions with cold
- 82 %
- 90 %
- 93 %
Worsening of the abnormalities observed at room temperature
Pattern changes

11. EMG guides toward myotonic syndrome genotypes
80 %
SCN4A
100 %
SCN4A
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