Lambert-Eaton Syndrome: Physiology

Clinical - Neuromuscular Diseases and Disorders, Physiology - Neurologic

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


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