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Eaton-Lambert Syndrome

(Eaton-Lambert's Syndrome)

By Michael Rubin, MDCM, Professor of Clinical Neurology, Weill Cornell Medical College; Attending Neurologist and Director, Neuromuscular Service and EMG Laboratory, New York Presbyterian Hospital-Cornell Medical Center

Eaton-Lambert syndrome is an autoimmune disorder that impairs communication between nerves and muscles, causing weakness.

  • Eaton-Lambert syndrome usually precedes, occurs with, or develops after certain cancers, especially lung cancer in men.

  • This syndrome causes muscle weakness (particularly in the legs), fatigue, dry mouth, drooping eyelids, and pain in the upper arms and thighs.

  • Doctors suspect Eaton-Lambert syndrome based on symptoms, but electromyography is necessary for diagnosis.

  • Treatment of the cancer, if present, can relieve symptoms, as can guanidine, and corticosteroids and plasma exchange help some people.

Nerves communicate with muscles by releasing a chemical messenger (neurotransmitter), which interacts with receptors on muscles (at the neuromuscular junction) and stimulates muscles to contract. Eaton-Lambert syndrome is caused by antibodies that interfere with the release of the neurotransmitter acetylcholine rather than attack acetylcholine receptors (as occurs in myasthenia gravis).

Eaton-Lambert syndrome usually precedes, occurs with, or develops after certain cancers. It most commonly occurs in men with tumors in their chest, especially lung cancer. Sometimes certain cancers trigger other disorders that are not cancerous, such as Eaton-Lambert syndrome. These disorders are called paraneoplastic syndromes.


Eaton-Lambert syndrome causes muscle weakness that tends to affect the larger muscles in the arms and, particularly, the legs. Typically, people have difficulty getting up from a chair, climbing stairs, and walking. Muscles may become weaker or cramp after they are used repeatedly. People also tire easily.

The mouth is dry, the eyelid droops, and the upper arms and thighs are painful.

Men may have erectile dysfunction.


  • Electromyography

Symptoms suggest Eaton-Lambert syndrome, but electromyography (stimulating muscles, then recording their electrical activity) is needed to confirm the diagnosis.


  • Treatment of cancer if present

  • Guanidine

  • Sometimes corticosteroids and plasma exchange

Treating cancer, if present, sometimes relieves symptoms due to Eaton-Lambert syndrome.

Guanidine, a drug that increases the release of acetylcholine, often lessens symptoms but may inhibit the bone marrow’s production of blood cells and impair liver function.

Corticosteroids and plasma exchange (filtering of toxic substances, including abnormal antibodies, from the blood) help some people.

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