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Lambert-Eaton Syndrome: Physiology

Myasthenic Syndrome (Lambert-Eaton) is caused by IgG antibodies to voltage-gated Ca++ channels in the musculature, which leads to increased sensitivity to both SCh and nondepolarizing muscle relaxants. Different from myasthenia gravis in both the type of muscles (proximal) and response to exercise (improvement with repetition, as opposed to increasing weakness in MG).

Associated with small-cell carcinoma of the lung, sarcoidosis, thyroiditis, collagen-related vascular disease.May be accompanied by autonomic nervous system defects, including gastroparesis, orthostatic hypotension, and urinary retention

Myasthenic Syndrome (Lambert Eaton)

  • IgG antibodies to voltage-gated Ca++ channels
  • Often seen in the setting of small-cell carcinoma of the lung (also sarcoidosis, thyroiditis, collagen-related vascular diseases)
  • Proximal muscle weakness, improves with repetitive effort
  • More susceptible to both SCh and non-depolarizing NMBDs
  • Titrate small doses of NMBDs to quantitative twitch monitoring
  • Beware gastroparesis and orthostatic hypotension in these patients

Other References

  1. Keys to the Cart for August 1, 2019 Link