Myoedema is a clinical finding that is associated with hypothyroid myopathy. It is caused by a focal, sustained muscle contraction that is electrically silent.
Myoedema can be triggered by tapping a muscle with tendon hammer or with a finger. The muscle swells over 1-2 seconds (“mounding”) then the swelling subsides over 5-10 seconds.
After resolution the muscle contour is smooth and there is no palpable hardening.
Mechanism: percussion or pressure causes release of calcium ion from muscle, which is followed by a delayed calcium reuptake by the sarcoplasmic reticulum.
The finding can:
(1) be an important finding in hypothyroid myopathy
(2) occur in malnutrition (hypoalbuminemia, vitamin deficiencies)
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