$Unique_ID{BRK03692} $Pretitle{} $Title{Eaton-Lambert Syndrome} $Subject{Eaton-Lambert Syndrome Lambert-Eaton Syndrome Lambert-Eaton Myasthenic Syndrome Myasthenic Syndrome of Lambert-Eaton Myasthenia Gravis Guillain-Barre Syndrome} $Volume{} $Log{} Copyright (C) 1990, 1991, 1992 National Organization for Rare Disorders, Inc. 794: Eaton-Lambert Syndrome ** IMPORTANT ** It is possible that the main title of the article (Eaton-Lambert Syndrome) is not the name you expected. Please check the SYNONYM listing to find the alternate names and disorder subdivisions covered by this article. Synonyms Lambert-Eaton Syndrome Lambert-Eaton Myasthenic Syndrome Myasthenic Syndrome of Lambert-Eaton Information on the following disorders can be found in the Related Disorders section of this report: Myasthenia Gravis Guillain-Barre Syndrome General Discussion ** REMINDER ** The information contained in the Rare Disease Database is provided for educational purposes only. It should not be used for diagnostic or treatment purposes. If you wish to obtain more information about this disorder, please contact your personal physician and/or the agencies listed in the "Resources" section of this report. Eaton-Lambert Syndrome is a neuromuscular disorder that may be an autoimmune disease. Major symptoms include muscle weakness and fatigue especially of the pelvic and thigh muscles. Other symptoms may include dryness of the mouth, impotence, pain in the thighs, and a pricking, tingling or creeping sensation on the skin (paresthesias) around the affected areas. Symptoms Eaton-Lambert Syndrome is characterized by weakness and fatigue especially of the pelvic and thigh muscles. Other symptoms may include dryness of the mouth, impotence, pain in the thighs, and a pricking, tingling or creeping feeling on the skin (paresthesias) around the affected areas. Some patients experience double-vision (diplopia), difficulty in articulation of speech (dysarthria), ptosis (drooping of the upper eyelid), decreased sweating, low blood pressure when in an upright position (orthostatic hypotension), and altered reflexes of the pupils of the eyes. Patients with Eaton-Lambert Syndrome may not have deep tendon reflexes and lower limbs are affected more often than upper limbs. Diagnosis of Eaton-Lambert Syndrome is made by EMG (electromyogram), which is a record of electrical activity of the muscles, and by electron microscopy. The EMG initially shows a small amount of electrical activity in the muscle. After stimulation or exercise, there is increased activity in the muscle. Electron microscopy (use of an electron microscope which magnifies tiny images such as bacteria or viruses and is 1000 times more powerful than an ordinary microscope) may show changes in the postsynaptic membrane and nerve terminal of nerve cells. Causes Eaton-Lambert Syndrome is suspected of being an autoimmune disorder. Autoimmune disorders are caused when the body's natural defenses (antibodies, lymphocytes, etc.), against invading organisms suddenly begin to attack healthy tissue. Eaton-Lambert Syndrome may involve autoantibodies directed against part of the terminals of nerves, causing a reduction in the amount of acetylcholine released at the place where the terminals of nerve cells meet the muscle (motor end plate) in response to a nerve impulse. When the nerve is repeatedly stimulated, it helps the release of acetylcholine, increasing possible muscle action. Acetylcholine is a chemical that helps "communication" between nerve cells and muscles. Two thirds of Eaton-Lambert Syndrome patients are people with cancer. Of Eaton-Lambert Syndrome patients over the age of 40, 70% of men and 30% of women will have a malignant tumor. The tumor is usually a small cell carcinoma of the lung. Eaton-Lambert Syndrome may occur up to three years before a tumor is detected. However, in one third of patients with this disorder, the syndrome is not related to cancer and may occur at any age. (For more information, choose "cancer" as your search term in the Rare Disease Database.) Affected Population Eaton-Lambert Syndrome is a rare disorder that affects males and females equally and tends to occur most often in patients with cancer, especially small-cell lung cancer (such as oat cell carcinoma of the lung). In one third of Eaton-Lambert patients, the syndrome is not related to cancer and may occur at any age. There are approximately 400 known cases of Lambert- Eaton Syndrome in the United States. Related Disorders Symptoms of the following disorders can be similar to those of Eaton-Lambert Syndrome Syndrome. Comparisons may be useful for a differential diagnosis: Myasthenia Gravis (MG) is a chronic neuromuscular disease characterized by weakness and abnormally rapid fatigue of the voluntary muscles, with improvement following rest. Any group of muscles may be affected, but those around the eyes and the muscles used for swallowing are the most commonly involved. In Eaton-Lambert Syndrome these head and neck muscles are usually not affected. Weakness of the limbs is a frequent characteristic of MG and is most pronounced at the end of the day and also after exercise. However, in patients with Eaton-Lambert Syndrome muscle strength tends to improve after exercise. (For more information on this disorder, choose "Myasthenia" as your search term in the Rare Disease Database). Guillain-Barre Syndrome is an autoimmune disease which occurs when the body's defense system attacks the nerves, damaging the nerve's myelin and axon. Nerve signals are delayed and altered, causing weakness and paralysis of the muscles of the legs, arms, and other parts of the body. Abnormal sensations such as numbness or tingling also occur. If muscle nerves are damaged, the patient experiences aching and weak muscles, shortness of breath, and difficulty in swallowing. If the autonomic nervous system is damaged, the patient may experience alterations of blood pressure, heart rate, vision, body temperature, bladder function, and blood chemistries. (For more information on this disorder, choose "Guillain" as your search term in the Rare Disease Database). Therapies: Standard Symptoms of patients with Eaton-Lambert Syndrome are often relieved or improved with Guanidine. This drug increases the release of acetylcholine in the muscles. Immunosuppressive drugs such as prednisone and azathioprine may also relieve symptoms. If cancer is present, treatment of Eaton-Lambert Syndrome first involves treatment directed at the cancer. This may result in relief of Eaton-Lambert symptoms as well. Other treatment is symptomatic and supportive. Therapies: Investigational The FDA has approved the following drug for testing as treatment for Eaton- Lambert Syndrome in patients: The orphan drug dynamine is being tested for treatment of Eaton-Lambert Syndrome. The drug is manufactured by Mayo Foundation, Rochester, MN. Plasmapheresis may be of benefit in some cases of Eaton-Lambert Syndrome. This procedure is a method for removing unwanted substances (toxins, metabolic substances and plasma parts) from the blood. Blood is removed from the patient and blood cells are separated from plasma. The patient's plasma is then replaced with other human plasma and the blood is retransfused into the patient. More research is needed before plasmapheresis can be recommended for use in all but the most severe cases of Eaton-Lambert Syndrome. The National Cancer Institute conducts clinical trials on new drugs being tested for lung cancer and other forms of cancer. To learn about locations of these investigations, contact the Cancer Information Service, 1-800-4- CANCER. Clinical trials are underway to study the orphan drug 3,4-diaminopyridine for the improvement of strength in patients with Eaton Lambert Syndrome. Interested persons may wish to contact: Donald B. Sanders, M.D. Box 3403 Duke University Medical Center Durham, NC 27719 (919) 684-6078 to see if further patients are needed for this research. This disease entry is based upon medical information available through January 1992. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder. Resources For more information on Eaton-Lambert Syndrome, please contact: National Organization for Rare Disorders P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 Myasthenia Gravis Foundation, Inc. 53 W. Jackson Blvd., Suite 1352 Chicago, IL 60604 1-800-541-5454 (312) 427-6252 NIH/National Institute of Neurological Disorders & Stroke (NINDS) 9000 Rockville Pike Bethesda, MD 20892 (301) 496-5751 (800) 352-9424 Muscular Dystrophy Association, National Office 3561 E. Sunrise Dr. Tucson, AZ 85718 (602) 529-2000 References CECIL TEXTBOOK OF MEDICINE, 18th Ed.: James B. Wyngaarden, and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1988. Pp. 1106, 1633, 2285, 2287. INTERNAL MEDICINE, 2nd Ed.: Jay H. Stein, ed.-in-chief; Little, Brown and Co., 1987. Pp. 999-1000. THE MERCK MANUAL, Volume 1, 14th Ed.: Robert Berkow, M.D., ed.-in-chief; Merck, Sharp, and Dohme Laboratories, 1982. Pp. 1213, 1450-1451. AUTONOMIC DYSFUNCTION IN LAMBERT-EATON MYASTHENIC SYNDROME. R. K. Khurana, et al.; J Neurol Sci (May 1988; issue 85 (1)). Pp. 77-86. EATON-LAMBERT SYNDROME AS A HARBINGER OF RECURRENT SMALL-CELL CARCINOMA OF THE CERVIX WITH IMPROVEMENT AFTER COMBINATION CHEMOTHERAPY. G. P. Sutton, et al.; Obstet Gynecol (Sept 1988; issue 72 (3 Pt 2)). Pp. 516-518. 3,4-DIAMINOPYRIDINE IN THE TREATMENT OF LAMBERT-EATON MYASTHENIC SYNDROME. McEvoy, K.M., N Eng J Med, (1989, issue 321). Pp. 1567-1571.