Periodic paralysis

• General Features
  • Hereditary channelopathies (mostly AD).
  • Episodic, painless flaccid paralysis + hyporeflexia.
  • Sensation is preserved.
• Hypokalemic Periodic Paralysis (HypoPP)
  • Channel: Voltage-gated calcium channel.
  • Labs: $\downarrow$ Serum $K^{+}$ during attack.
  • Trigger: High-carb meals (insulin drive K+ intracellularly), rest after exercise.
  • Tx: Oral Potassium (acute); Acetazolamide (prophylaxis).
• Hyperkalemic Periodic Paralysis (HyperPP)
  • Channel: Voltage-gated sodium channel.
  • Labs: $\uparrow$ Serum $K^{+}$ during attack.
  • Trigger: Fasting, cold, $K^{+}$-rich foods.
  • Assoc: Myotonia (delayed relaxation).
  • Tx: Glucose/Insulin (acute); Acetazolamide or Thiazides (prophylaxis).
• Thyrotoxic Periodic Paralysis
  • Demographics: Young Asian males.
  • Assoc: Hyperthyroidism (Graves’).
  • Presentation: Similar to HypoPP ($\downarrow K^{+}$).
  • Tx: Beta-blockers + Treat underlying thyroid disease.