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 and nerve conduction studies are necessary for diagnosis.
Treatment of the cancer, if present, sometimes relieves symptoms, as can amifampridine or guanidine, and plasma exchange or various other drugs may help some people.
(See also Overview of Neuromuscular Junction Disorders Overview of Neuromuscular Junction Disorders Nerves connect with muscles at the neuromuscular junction. There, the ends of nerve fibers connect to special sites on the muscle’s membrane called motor end plates. These plates contain receptors... read more .)
Nerves Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more communicate with muscles by releasing a chemical messenger (neurotransmitter), which interacts with receptors on muscles (at the neuromuscular junction Overview of Neuromuscular Junction Disorders Nerves connect with muscles at the neuromuscular junction. There, the ends of nerve fibers connect to special sites on the muscle’s membrane called motor end plates. These plates contain receptors... read more ) 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 Myasthenia Gravis Myasthenia gravis is an autoimmune disorder that impairs communication between nerves and muscles, resulting in episodes of muscle weakness. Myasthenia gravis results from malfunction of the... read more ).
Eaton-Lambert syndrome usually precedes, occurs with, or develops after certain cancers—for example, as a paraneoplastic syndrome Paraneoplastic Syndromes Paraneoplastic (associated with cancer—see also Overview of Cancer) syndromes occur when a cancer causes unusual symptoms due to substances that circulate in the bloodstream. These substances... read more . Paraneoplastic syndromes result from substances produced by the cancer or by the immune system in response to the cancer. Eaton-Lambert syndrome most commonly occurs in men with tumors in their chest, especially lung cancer.
Symptoms of Eaton-Lambert Syndrome
Eaton-Lambert 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 Overview of the Cranial Nerves Twelve pairs of nerves—the cranial nerves—lead directly from the brain to various parts of the head, neck, and trunk. Some of the cranial nerves are involved in the special senses (such as seeing... read more ) 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.
Diagnosis of Eaton-Lambert Syndrome
Electromyography and nerve conduction studies
Doctors suspect Eaton-Lambert syndrome based on symptoms. However, electromyography and nerve conduction studies Electromyography and Nerve Conduction Studies Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more 
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 Eaton-Lambert Syndrome
Treatment of cancer if present
Amifampridine
Guanidine
Sometimes various other drugs or plasma exchange
Treating cancer, if present, sometimes relieves symptoms due to Eaton-Lambert syndrome.
Amifampridine, a drug that increases the release of acetylcholine, can improve symptoms but cannot be taken in people with a history of seizures.
Guanidine, another 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.
Various other drugs or measures may help people whose disease does not respond to amifampridine or guanidine. For example, plasma exchange Plateletpheresis (platelet donation) In addition to normal blood donation and transfusion, special procedures are sometimes used. In plateletpheresis, a donor gives only platelets rather than whole blood. Whole blood is drawn from... read more (filtering of toxic substances, including abnormal antibodies, from the blood) may help some people. Pyridostigmine, azathioprine, rituximab, mycophenolate, or intravenous immunoglobulin (IVIG) may also be tried.
