Familial Periodic Paralysis



Familial Periodic Paralysis





Episodic bouts of limb weakness. Inherited “channelopathies” (inherited abnormalities of ion channels). Clinical features in Table 127.1.


Hypokalemic Periodic Paralysis (HoPP)

Serum potassium decreases in spontaneous attack to <3.0 mEq/L.

Usually maps to gene for dihydropyridine-sensitive L-type calcium channel of muscle (CACNL1A3, chromosome 1q31); sometimes maps to same gene as hyperkalemic periodic paralysis (SCN4A; see below).


Epidemiology

Rare. M:F ratio 1:1 to 3:2.


Symptoms and Signs

Attack starts after period of rest or ingestion of meal high in carbohydrates. Paralysis ranges from slight weakness of legs to complete paralysis of all limb muscles. Tendon reflexes may be absent. Oropharyngeal, respiratory muscles usually spared. Lasts 1 to 48 hours.



  • Frequency: one attack per year to several per day.


  • Between attacks: usually normal strength, normal serum potassium. Mild-to-severe proximal limb weakness persists in some patients.


Course

First attack usually around puberty (range 4 to 70 years). Frequency decreases with time; may cease after age 40. Rarely fatal.









Table 127.1 Clinical Features of Hypokalemic and Hyperkalemic Periodic Paralysis and Paramyotonia



























































  Hypokalemic periodic paralysis (HoPP) Hyperkalemic periodic paralysis (HyPP) Paramyotonia congenita
Age of onset Usually second or latter part of first decade First decade First decade
Sex Male preponderance Equal Equal
Incidence of paralysis Interval of weeks or months Interval of hours or days May not be present; otherwise, interval of weeks or months
Degrees of paralysis Tends to be severe Tends to be mild but can be severe Tends to be mild but can be severe
Effect of cold May induce an attack May induce an attack Tends to induce an attack
Effect of food (especially glucose) May induce an attack Relieves an attack Relieves an attack
Serum potassium Low High Tends to be high
Oral potassium Prevents an attack Precipitates an attack Precipitates an attack
Precipitants Food, cold Fasting, stress, rest after exercise, potassium-rich foods Fasting, stress, rest after exercise
Myotonia Absent Present Present
Modified from Hudson AJ. Brain 1963;86:811.

Only gold members can continue reading. Log In or Register to continue

Related posts:

Default ThumbnailNerve Conduction Studies, Electromyography, and Magnetic Stimulation Default ThumbnailSpirochete Infections: Neurosyphilis Default ThumbnailCerebral Veins and Sinuses Default ThumbnailStructural Malformations Default ThumbnailMyoclonus Default ThumbnailMénière Syndrome

Stay updated, free articles. Join our Telegram channel
Tags:
Jul 27, 2016 | Posted by in NEUROLOGY | Comments Off on Familial Periodic Paralysis

Full access? Get Clinical Tree
Get Clinical Tree app for offline access