$Unique_ID{BRK03882} $Pretitle{} $Title{Isaacs' Syndrome} $Subject{Isaacs' Syndrome Continuous Muscle Fiber Activity Syndrome Neuromyotonia Quantal Squander Neuromyotonia Generalized sporadic Neuromyotonia Generalized familial Neuromyotonia Focal Hallervorden-Spatz Disease Paraplegia Hereditary Spastic Stiff Man Syndrome } $Volume{} $Log{} Copyright (C) 1991 National Organization for Rare Disorders, Inc. 758: Isaacs' Syndrome ** IMPORTANT ** It is possible that the main title of the article (Isaacs' 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 Continuous Muscle Fiber Activity Syndrome Neuromyotonia Quantal Squander Disorder Subdivisions: Neuromyotonia, Generalized - sporadic Neuromyotonia, Generalized - familial Neuromyotonia, Focal Information on the following disorders can be found in the Related Disorders section of this report: Hallervorden-Spatz Disease Paraplegia, Hereditary Spastic Stiff Man 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. Isaacs' Syndrome is a peripheral motor neuron disorder characterized by muscular stiffness and cramping, particularly in the limbs. Continuous fine vibrating muscle movements (myokymia) can be seen. Muscle relaxation may be difficult especially after physical activity involving the particular muscle(s). These symptoms occur even during sleep. Symptoms In Isaacs' Syndrome, involuntary continuous muscle fiber activity may cause stiffness and delayed relaxation in the affected muscles. Continuous fine vibrating muscle movements (myokymia) may occur along with these symptoms. Walking may be difficult. Isaac's Syndrome may be generalized or focal. When it is focal, muscle relaxation following voluntary muscle movement is delayed in the affected muscle(s) so that the patient may be an unable to open his or her fist or eyes immediately after closing them tightly for a few seconds. Diagnosis of Isaacs' Syndrome is accomplished by using an instrument that measures electrical activity occurring in a muscle (electromyography or EMG). A person with Isaacs' Syndrome will register abnormal electrical activity in the muscle(s), and the peripheral nerves. Causes Isaacs' Syndrome is caused by abnormal nerve impulses from the peripheral nerves. The impulses cause continuous muscle fiber activity which may continue even during sleep. There are three types of Isaacs' Syndrome; each one develops from a different cause: In the generalized-sporadic type of Isaacs' Syndrome, intrathoracic malignancy such as a tumor (located between the neck and abdomen) may be the cause. Peripheral neuropathy may be linked with the generalized-familial type of Isaacs' Syndrome, which tends to occur in families. This type of Isaacs' Syndrome may be inherited through an autosomal dominant gene. Human traits including the classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the normal gene and resulting in appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child. (For more information, choose "Peripheral Neuropathy" as your search term in the Rare Disease Database). The focal form of Isaacs' Syndrome may occur as a result of lesions on the peripheral nerves. The cause of the lesions is often unknown. Affected Population Isaacs' Syndrome is a rare disorder affecting males and females of all ages in equal numbers. Related Disorders Symptoms of the following disorders can be similar to those of Isaacs' Syndrome. Comparisons may be useful for a differential diagnosis: The patient with Hallervorden-Spatz Disease may develop symptoms resembling dystonia (a slow, steady muscle contraction distorting limbs, neck, face, mouth or trunk into certain positions), muscular rigidity (uncontrolled tightening of the muscles), and choreoathetosis (spontaneous, non-repetitive, slow writhing movements, usually of the extremities). Muscle spasms are present in one third of affected individuals. Less common symptoms are dysarthria (difficulty in speaking), mental retardation, facial grimacing, dysphasia (impaired speech), muscle atrophy (shrinking muscles) and seizures. Symptoms vary in different individuals. (For more information on these disorders, choose "Hallervorden-Spatz" or "Dystonia" as your search terms in the Rare Disease Database). Initial symptoms of Hereditary Spastic Paraplegia usually include weakness, muscle spasms, and stiffness of the legs. Leg muscles may contract or a heel deformity may occur making walking difficult. Speech disturbances can also appear. Difficulty in swallowing, exaggeration of tendon reflexes and general muscle weakening may develop as this disorder progresses. Symptoms can range from mild to severe depending upon the mode of inheritance (dominant or recessive genes), and the degree to which the nerves are compressed or damaged. (For more information on this disorder, choose "paraplegia" as your search term in the Rare Disease Database). Stiff Man Syndrome is a very rare neurological disorder. It is characterized by progressive rigidity and spasms of the voluntary muscles of the neck, trunk, shoulders, and proximal extremities. It is caused by abnormal nerve activity most likely in the central, rather than peripheral, nervous system. The electrical activity measured by the EMG may begin in the spinal cord, rather than the peripheral nerves. (For more information on this disorder, choose "stiff-man" as your search term in the Rare Disease Database). Therapies: Standard Isaacs' Syndrome may be treated with anticonvulsant drugs such as phenytoin or carbamazepine, which may stop the abnormal impulses and prevent the symptoms from reoccurring. Genetic counseling may be of benefit for patients and their families with inherited forms of Isaacs' Syndrome. Other treatment is symptomatic and supportive. Therapies: Investigational Research on Isaacs' Syndrome indicates that inhalation of oxygen may help muscle relaxation and hand spasms but not myokymia (continuous fine vibrating muscle movements). These movements are usually found to be relieved with the anticonvulsant drug phenytoin. Surgery, entailing motor nerve block and/or block of the afferent sensitive fibers (which send impulses to the brain or spinal cord), may help some patients when drug therapies are ineffective. This disease entry is based upon medical information available through June 1991. 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 Isaacs' Syndrome, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 The National Arthritis and Musculoskeletal and Skin Diseases (NIAMS) Information Clearinghouse Box AMS Bethesda, MD 20892 (301) 495-4484 For genetic information and genetic counseling referrals: March of Dimes Birth Defects Foundation 1275 Mamaroneck Avenue White Plains, NY 10605 (914) 428-7100 Alliance of Genetic Support Groups 35 Wisconsin Circle, Suite 440 Chevy Chase, MD 20815 (800) 336-GENE (301) 652-5553 References CECIL TEXTBOOK OF MEDICINE, 18th Ed.: James B. Wyngaarden, and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1988. Pp. 2284. HYPOXIA-SENSITIVE HYPEREXCITABILITY OF THE INTRAMUSCULAR NERVE AXONS IN ISAACS' SYNDROME. K. Oda, et al.; Ann Neurol (February 1989 issue 25 (2)). Pp. 140-145. ISAACS' SYNDROME. T.J. Brown; Arch Phys Med Rehabil (Jan 1984 issue 65 (1)). Pp. 27-29. ISAACS' SYNDROME WITH MUSCLE HYPERTROPHY REVERSED BY PHENYTOIN THERAPY. J. Zisfein, et al.; Arch Neurol (April 1983 issue 40 (4)). Pp. 241-242.