Thread by @DrSherani432

1) MYOTONIA
Pure stiffness : Chloride channelopathy
Pure periodic weakness : Calcium + Potassium Channalenopathy
Overlapping Syndrome: (Myotonia, Paramyotonia, HyperKK, HypoKK) Sodium Channelopathy
A=CHLORIDE CHANNEL (Myotonia congenita)
Chloride channelopathy(CLCN1) ,Family

2) Hx, Two forms, face + limbs(distal muscles)
AD#Thomson early onset, Less severe, muscle hypertrophy.
AR#Beckor.. Late onset, more severe, shows warm up phenomenon.
Dx:
CMAP amplitude decrement short post-exercise which rapidly returns to baseline. Decrement that repairs

3) with repeated trials. Cooling no affect.
Rx:
Mexelitine,Tegral, Phenytoin, Procainamide.
All muscle membrane stabilizers by blocking Sodium Channels.

B=Na CHANNEL (paramyotonia congenita)
Proximal + distal limbs muscles, face, neck.
Worse with cold + exercise
SCN4A

4) Channelopathy, AD, also called paradoxical myotonia(that worsen with exercise)
Some Are Na Channel Myotonia... Also K-aggrevating myotonia(sensitivity to K-Load/K-rich foods), not response to cold or associated weakness.
EMG:
CMAP amplitude dropping by repetitive short

5) exercises or Cold Exposure.
Treatment:
Same chloride channel... Tegral,Mexelitine, Procainamide except Acetazolamide Responsive Myotonia (one of K-aggrevating Myotonia)

Other Na-Channel Myotonia (K-aggrevated)
1-Acetzaolamide Responsive Myotonia: Symptoms improve with

6) Acetazolamide.
2-Myotonia Fluctuans: Fluctuations in Myotonia and increased muscle stiffness after delayed  like after 20 minutes after exercise.
3-Myotonia Permenans: Cause severe persistent Myotonia

C=PERIODIC PARALYSIS
Caused by Na-Channel(SCN4A), Ca-Channel(CACNA1S),

7) K-Channel (KCNJ2)
Presentations:
Episodes of Flaccid weakness, Changes in Potassium (High/Low during attack, Normal Between the Attacks), onset before 20 years,
Drop in CMAP about 40% after sustained period of exercise after 20-30 minutes.
Attacks:
Triggered by

8) Carbohydrates or food rich in potassium, or Rest after Exercise.
Biopsy :
Chronic Myopathic changes, vacoules, or tubular aggregates.
Treatment:
Carbonic Anhydrase inhibitors (Acetazolamide or Dichlor-phenamide) decrease frequency and paralytic Episodes.

HYPERKALEMIC

9) PERIODIC PARALYSIS
Na-channels, AD, Duration in hours,
Flaccid episodic, Symmetrical, Proximal muscle weakness. Spares face, bulber, respiratory muscles.
Early morning before eating, rest after exercise, Fasting, K-load.
Reflexes are reduced, Weakness provoked by

10) exercise, K-Load, Fasting, stress, pregnancy, ethanol, Steriods.
Labs:
Increased K during attack, increased CK during attack, Oral K load during Fasting can induce attack,
CMAP... Increases greater than normal after 5 minutes sustained exercise, and reduces 40% or more

11) after resting 20-40 minutes.50% have Myotonic discharges.
Biopsy: Vacoular Myopathy
Treatment:
IV carbohydrates in acute attacks, Acetazolamide, thiazide, Dichlorphenamide in future attacks.

HYPOKALEMIC PERIODIC PARALYSIS
AD, Duration hours - days,
Flaccid episodes of

12) weakness, Symmetrical, Legs>Arms, onset teen ages. Males>Females.
Provoked by Carbohydrates ingestion and Relieve by K-Intake. Glucose + Insulin induce attack.
CACNA1S, SCN4A, KCNE2.
LABS:
K level usually <2-3 mEq/L, CK may raised during attacks.
CMAP... Amplitudes

13) decrease during attack and increase immediately after sustained 5 minutes exercise. In severe effected persons, after initial increments, than there is progressive reduction in CMAP amplitude during rest 20-40 minutes. No Myotonic discharges.
Treatment:
Potassium intake,

14) Acetazolamide

@threadreaderapp plz unroll