Myotonia Flashcards
Define myotonia
tonic spasm after forceful voluntary contraction
T or F. Like cramps myotonic spasm is painful.
F. Painless. But sometimes with post myotonia nocturnal myalgia
Describe myotonia congenita in terms of
- Reaction to cold
- Affecting cardiac and smooth muscles
- Affecting EOMs
- Gestalt
- Facies
- State after rest
- Exaggerates. BUT not as bad with paramyotonia congenita
- NONE
- May cause strabismus
- Hypertrophied muscles. COMPARE with Myotonic dystrophy
- None. COMAPRE WITH Myotonic dystrophy
- Worse. Needs warm-up movements
READ MEGA TABLE!!
What chloride ion channel is affected in myotonia congenita?
CLCN1
What are the recommended drugs for myotonia?
Quinine
Procainamide
Phenytoin
Hyperkalemic periodic paralysis, Myotonia fluctuans and paramyotonia congenita are due to mutation in the gene encoding the alpha subunit of the membrane bound voltage gated sodium channel in the skeletal muscle
SCN4A
In hyperkalemic PP what is the level of:
- Na during attack
- K during attack
- K in between attack
- Low
- 5-6 mmol/L
- Normal
Which diseases? HyperK PP, MC, PMC
- Occurs after a period of rest after exercise
- Increases with Exercise
- Occurs After cold exposure
- No warm-up phenomenon
- With warm up phenomenon
- Hyperkalemic PP and myotonia congenita
- Paramyotonia congenita
- ALL. But PMC is the WORST
- PMC
- MC, HyperK PP
What is the tx for HyperK PP
Acute attack: Glucose, Calcium
Low potassium diet
Acetazolamide 125-250 BID for prevention
What are the triggers for Hypokalemic Periodic Paralysis?
Exercise
Carbo loading
T or F: EMG evidence of myotonia EXCLUDES hyPOk PP
T
What is the pathologic change seen in hypokalemic periodic paralysis?
Vacuolization of the sarcoplasmic reticulum
Tx for HyPOK PP?
Acetazolamide
Spironolactone
Daily 5-10g of KCl UNsweetened solution
Acute: 0.25mEq KCl/kg or 0.1meq per kg bolus in mannitol 5% AVOID NSS and glucose
How does Acetazolamide work for HyPO vs HyPER K PP?
PO: induces acidosis
What drugs commonly trigger malignant hyperthermia?
Halothane and succinylcholine
How does dantrolene work for malignant hyperthermia?
prevents the release of Calcium from the SR
What are the components of the Andersen syndrome?
Defect in the KCNJ2 gene results in:
Potassium sensitive weakness
Ventricular dysrhythmias with long QT syndrome
Facies
Re: Thomsen disease
- Aka?
- Relationship to exercise
- Treatment?
- Inheritance pattern
- Relationship to rest
- Mutation in what ion channel?
- Aka? Myotonia congenita
- Relationship to exercise: Appears after
- Treatment? Mexiletine, quinine, procainamide, phenytoin
- Inheritance pattern: Dominant
- Relationship to rest: Noticeable after a period of inactivity
- Mutation in what ion channel? Chloride (CLCN1 gene CLC1 channel protein)
REMEMBER THAT UNLIKE CRAMPS THIS IS NOT PAINFUL
How to differentiate myotonia congenita from myotonic dystrophy?
MC has NO typical facies of MD: narrow face, frontal balding, cataracts
Also MC patients have muscle hypertrophy– a feature NOT prsent in MD pxs
Also MD is usually NOT present in the first few years of life, whereas MC already presents with slow opening of eyes after crying or sneezing and the legs may be conspicuously stiff ast he child tries to take its first steps.
Although seen in virtually all forms of myotonia, stiffness exaggerated by cold is most characteristic of?
Paramyotonia congenita
What is aka as a milder myotonia congenita with a later onset?
Myotnoia levior