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Periodic paralysis

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Periodic paralysis

- rare grp of disorders
- mostly inherited as autosomal dominant traits

Hypokalaemic periodic paralysis

Aetiology & epidemiology

- 1/3 cases sporadic
- remainder predominantly inherited but in young men, particularly Latin Americans & Orientals may occur in association with TTX

Pathophysiology

- disturbance in ATP-sensitive potassium channel in skeletal muscle. Seems to be excessive potassium transport into muscle, especially in response to insulin. Total body potassium is normal

Clinical features

- usually presents in adolescence
- attacks vary widely in frequency and duration
- may be precipitated by high CHO or sodium meals
- affects bulbar & and respiratory muscles rarely
- +/- cardiac arrhythmias during death
- examination between attacks is normal

Investigations

- hypokalaemia during attacks. Not profound
- provocative testing with glucose and insulin can be done to make diagnosis between attacks but if may be hazardous

Managment

- acute attacks respond to potassium
- potassium not effective in prophylaxis. Best agent appears to be acetazolamide: may block flux of potassium into muscle. Effectiveness may be related to metabolic acidosis

Potassium-sensitive periodic paralysis

- hyper/normokalaemic
- clear evidence of autosomal dominant transmission more common
- attacks briefer, more frequent and less severe (never fatal). Bulbar and respiratory involvement less likely
- +/- myotonia
- attacks usually precipitated by fasting, rest after exercise
- provocative testing with potassium is positive
- potassium normal/moderately raised during attacks
- manage acute attacks with oral glucose/CHO.


© Charles Gomersall December 1999

 

©Charles Gomersall, February, 2015 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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