Myotonic disorders!
“after a fright, or in an unexpected joyous movement, this convulsive constriction occurs in all limbs…the victim can not stand upright”
Prussian physician Asmus Julius Thomas Thomsen (1815–1896)
2) Definition
“difficulty in relaxation of a muscle after maximum voluntary contraction”
It can be specifically
- aggravated by conditions
- affecting regions of the body
- triggered
3) Myotonic or Tennessee fainting goat
“important in history due to role of chloride channel in muscle excitation”
- 1880s, Marshall County
- CLCN1 gene
4) Classification of myotonic disorders
5) Electrophysiology
Waxing & wanning of both amplitude & frequency
Potentials
- repetitive discharges
- 2 types: biphasic (<5ms) and positive waves (5-20ms)
7) Electrical myotonia differential
8) Eyelid myotonia
“tries to open his eyes after having squeezed them tight”
- persist 1-2 minutes
- recruit additional muscles: frontalis
3) Myotonic or Tennessee fainting goat
4) Classification of myotonic disorders
5) Electrophysiology
6) Dive-bomber
“High frequency discharges in EMG that vary in amplitude & frequency, waxing & waning continuously with firing frequencies ranging from 150/second down to 20/second and producing a sound that has been referred to as a dive bomber sound
*turn sound on
7) Electrical myotonia differential
8) Eyelid myotonia
9) Tongue myotonia
10) Handgrip myotonia
“make a fist and then fully open the hand”
- open of the fist require other hand
11) Handgrip myotonia
12) Warm-up phenomenon vs paramyotonia
13) Lid lag myotonia
14) Tented Mouth
“triangular appearance of the oral aperture with the apex in the midpoint of the upper vermilion and the lower vermilion forming the base”
- congenital myotonic dystrophy
15) Herculean appearance
16) Toe-extension myotonia
17) Smooth muscle myotonia
18) Myotonic dystrophies
DM 1
- CTG trinucleotide repeat on DMPK gene
- most common myotonic disorder
DM 2
- CCTG tetranucleotide repeat on CNBP gene
- rare disorder
19) Myotonic dystrophy mnemonic
20) Nondystrophic myotonia
21) Nondystrophic myotonia - chloride channel
22) Nondystrophic myotonia – sodium channel
23) Potassium-sensitive myotonia (potassium-aggravated myotonia)
24) Paramyotonia congenita
Paradoxical myotonia
1st signs of stiffness as prolonged eye closure, after
- crying
- sleep near a fan
- washing face w/ cold water
25) Hyperkalemic periodic paralysis
“early childhood w/ episodes of periodic weakness”
- attacks in the morning & fasting
- 3 variants: HyperKPP w/o myotonia; w/ myotonia; w/ paramyotnia
26) Schwartz-Jampel syndrome (chondrodystrophic myotonia)
"prominent and diffuse myotonia that is present at birth"
27) Electrodiagnostic tests