Paralysis, Periodic

Episodes of flaccid weakness or paralysis occur, sometimes in association with abnormal plasma potassium level

May have a familial (dominant inheritance) basis

The hypokalemic variety is commonly associated with hyperthyroidism in young Asian men

Hypokalemic periodic paralysis

• Attacks tend to occur on awakening, after exercise, or after a heavy meal and may last for several days

• Strength is normal between attacks

Hyperkalemic periodic paralysis: attacks also tend to occur after exercise but usually last for < 1 h

Normokalemic periodic paralysis: similar clinically to the hyperkalemic variety, but the plasma potassium level remains normal during attacks

Clinical diagnosis combined with plasma potassium and, when relevant, thyroid function tests (free T₄, TSH)

Hypokalemic periodic paralysis

• Patients should avoid excessive exertion

• Attacks may be prevented by a low-carbohydrate, low-salt diet; acetazolamide, 250–750 mg once daily orally; nonselective beta-adrenergic blockers

• An ongoing attack may be aborted by potassium chloride given orally or by intravenous drip, provided the ECG can be monitored and kidney function is satisfactory

• Treatment of associated hyperthyroidism prevents recurrences

Hyperkalemic periodic paralysis

• Attacks may be terminated by intravenous calcium gluconate (1–2 g) or by intravenous diuretics (furosemide, 20–40 mg), glucose, or glucose and insulin

• Daily acetazolamide or chlorothiazide may prevent recurrences

Normokalemic periodic paralysis

• Treatment is with acetazolamide, 250–750 mg once daily orally