Lambert-Eaton myasthenic syndrome is a rare autoimmune neuromuscular disorder that impairs communication between nerves and muscles, causing weakness.
Lambert-Eaton myasthenic syndrome usually precedes, occurs with, or develops after certain cancers, especially small cell 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 Lambert-Eaton syndrome based on symptoms, but electromyography and nerve conduction studies are necessary for diagnosis.
Treatment of the cancer, if present, sometimes relieves symptoms. Additionally, medications (such as amifampridine or guanidine) and plasma exchange may help some people.Treatment of the cancer, if present, sometimes relieves symptoms. Additionally, medications (such as amifampridine or guanidine) and plasma exchange may 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. Lambert-Eaton syndrome is caused by antibodies that interfere with the release of the neurotransmitter acetylcholine rather than attack acetylcholine receptors (as occurs in myasthenia gravis).
Lambert-Eaton syndrome usually precedes, occurs with, or develops after certain cancers—for example, as a paraneoplastic syndrome. Paraneoplastic syndromes result from substances produced by the cancer or by the immune system in response to the cancer. Lambert-Eaton syndrome most commonly occurs in men with tumors in their chest, especially lung cancer.
Symptoms of Lambert-Eaton Syndrome
Lambert-Eaton syndrome causes muscle weakness that tends to begin in the hip and thigh muscles, then typically spreads to the shoulder muscles, and then down the arms and legs to the hands and feet. The nerves that connect the head, face, eyes, nose, and ears to the brain (cranial nerves) are affected last.
Typically, people have difficulty getting up from a chair, climbing stairs, and walking. Muscle strength may temporarily improve after the muscles are used repeatedly, but the muscles then weaken again and cramp. People also tire easily.
The mouth is dry, the eyelid droops, and the upper arms and thighs are painful.
Men may have erectile dysfunction.
Diagnosis of Lambert-Eaton Syndrome
Electromyography and nerve conduction studies
Doctors suspect Lambert-Eaton syndrome based on symptoms. However, electromyography and nerve conduction studies are needed to confirm the diagnosis. Electromyography involves inserting a needle into a muscle to record its electrical activity. Nerve conduction studies are done to measure the speed that an electric impulse travels along a nerve.
Treatment of Lambert-Eaton Syndrome
Treatment of cancer if present
AmifampridineAmifampridine
Guanidine
Sometimes various other medications or plasma exchange
Treating cancer, if present, sometimes relieves symptoms due to Lambert-Eaton syndrome.
Amifampridine, a medication that increases the release of acetylcholine, can improve symptoms but cannot be taken in people with a history of seizures.Amifampridine, a medication that increases the release of acetylcholine, can improve symptoms but cannot be taken in people with a history of seizures.
Guanidine, another medication that increases the release of acetylcholine, often lessens symptoms but may inhibit the bone marrow’s production of blood cells and impair liver function.
Various other medications or measures may help people whose disease does not respond to amifampridine or guanidine. For example, plasma exchange (filtering of toxic substances, including abnormal antibodies, from the blood) may help some people. Pyridostigmine, azathioprine, rituximab, mycophenolate, or intravenous immune globulin (IVIG) may also be tried.(filtering of toxic substances, including abnormal antibodies, from the blood) may help some people. Pyridostigmine, azathioprine, rituximab, mycophenolate, or intravenous immune globulin (IVIG) may also be tried.
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