What is the inheritance pattern of hypokalemic periodic paralysis? Hyperkalemic periodic paralysis?
autosomal dominant for both
What precipitates hyperkalemic periodic paralysis?
dehydration (exercise and fasting)
potassium-rich foods
What precipitates hypokalemic periodic paralysis?
hyperglycemia (insulin burst leads to hypokalemia)
hyperventilation (alkalosis leads to hypokalemia)
viral illness
rest following exercise
Is an extremity affected by a stroke more or less sensitive to non-depolarizing muscle relaxants?
less sensitive due to extrajunctional receptors
*true of all upper motor neuron conditions*
Is cerebral palsy a contraindication for succinylcholine?
No
*CP patients do not develop extrajunctional receptors*
Is MS a contraindication to succinylcholine?
a relative contraindication, more absolute in the presence of significant paresis
Why is succinylcholine contraindicated in Duchenne’s muscular dystrophy? Myotonic dystrophy? ALS? Guillain Barre syndrome?
DMD: hyperkalemia from disrupted myocyte membrane
MyoD: persistent contractures preventing intubation and ventilation
ALS and GBS: hyperkalemia from extrajunctional receptors
What should be avoided to prevent sustained contractures in patients with myotonic dystrophy?
succinylcholine
anti-cholinesterases (e.g., neostigmine)
hypothermia
Does myasthenia gravis affect skeletal muscle, smooth muscle, or both?
only skeletal muscle
How do you distinguish between weakness from worsening myasthenia and a cholinergic crisis?
edrophonium challenge (e.g., tensilon test)
Which factors increase the risk of post-op ventilation in pateints with myasthenia gravis?
disease duration > 6 years
vital capacity < 2.9 L
pyridostigmine dose > 750 mg/day
concomitant respiratory disease
How are infants of mothers with myasthenia gravis affected?
They can have myasthenia for up to 3 weeks.
How does Eaton-Lambert myasthenia syndrome affect sensitivity to muscle relaxants?
More sensitive to succinylcholine due to upregulated AChRs
More sensitive to non-depolarizing agents due to less ACh to compete with