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For further information, see CMDT Part 24-35: Disorders of Neuromuscular Transmission

Key Features

  • There is defective release of acetylcholine in response to a nerve impulse, leading to weakness, especially of the proximal muscles of the limbs

  • May be associated with small-cell carcinoma, sometimes developing before the tumor is diagnosed, and occasionally occurs with certain autoimmune diseases (eTable 39–1)

eTable 39–1.Paraneoplastic syndromes associated with cancer.

Clinical Findings

  • Variable weakness, typically improving with activity

  • Dysautonomic symptoms may also be present

  • A history of malignant disease may be obtained

  • Unlike myasthenia gravis, power steadily increases with sustained contraction


  • Electrophysiologic diagnosis: the muscle response to stimulation of its motor nerve increases remarkably after exercise or if ...

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