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Adynamia episodica hereditaria: what causes the weakness?
K Ricker1, L M Camacho, P Grafe
1Neurologische Universitätsklinik Würzburg, Federal Republic of Germany.
Muscle & Nerve
|November 1, 1989
Summary
Adynamia episodica hereditaria causes periodic paralysis via exercise and rest, linked to hyperkalemic periodic paralysis. Cold exposure induces distinct muscle weakness by altering excitability, differing from paramyotonia congenita.
Area of Science:
- Neurology
- Muscle Physiology
Background:
- Investigated a patient with adynamia episodica hereditaria presenting with unexplained weakness.
- Adynamia episodica hereditaria is a rare genetic disorder affecting muscle function.
Observation:
- Exercise and rest triggered episodes of hyperkalemic periodic paralysis.
- Forearm cooling induced localized muscle weakness.
- Isolated intercostal muscle studies revealed a non-inactivating sodium current in high potassium concentrations, causing muscle fiber depolarization.
Findings:
- The observed muscle weakness in adynamia episodica hereditaria is due to an abnormal sodium conductance.
- Cold-induced weakness in this patient involves reduced muscle excitability and increased mechanical threshold, distinct from paramyotonia congenita.
- Intracellular recordings confirmed increased intracellular sodium levels.
Implications:
- Elucidates the distinct pathomechanisms of exercise-induced and cold-induced weakness in adynamia episodica hereditaria.
- Differentiates the cold-induced weakness in adynamia episodica hereditaria from that seen in paramyotonia congenita.
- Provides insights into sodium channel dysfunction in periodic paralysis disorders.