Genetic and Rare Diseases Information Center (GARD)


Other names people use for this condition
  • Neuromyotonia
  • Isaac's-Merten's syndrome
  • Continuous muscle fiber activity syndrome
  • Quantal squander syndrome
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Isaacs syndrome
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I was diagnosed with Isaac's syndrome over 4 years ago. Very few doctors are familiar with this condition and how to treat it. I would appreciate any information or help you could provide.



  • What is Isaac's syndrome? (Back to Top)

  • Isaac's syndrome is a neuromuscular disease caused by continuous signaling of the end regions of peripheral nerve fibers that activate muscle fibers (motor neurons). Age of onset is between ages 15 and 60, with most patients experiencing symptoms before age 40. There are hereditary and acquired forms of the disorder. The acquired form may develop in association with peripheral neuropathies or as an autoimmune condition.[1]

  • Last Reviewed: 5/12/2008

  • What causes Isaac's syndrome?
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  • The exact causes of Isaac's syndrome are not well understood. There are hereditary and acquired forms of the disorder.  [1] The acquired form has been associated with neoplasms, thymoma, myasthenia gravis, lymphomas, peripheral neuropathies, and a variety of autoimmune nervous system disorders.[1][2] Isaac's syndrome has also been  seen in patients with systemic illnesses (eg, thyrotoxicosis (excessive thyroid hormone levels), uremia (kidney failure)) and following binge consumption of alcohol, exposure to toxins, timber rattlesnake bite, gold therapy, and penicillamine therapy.
     
    Familial Isaac's syndrome appears to be inherited in an autosomal dominant manner.[3] 



  • Last Reviewed: 5/12/2008

  • What symptoms have been associated with Isaac's syndrome?
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  • Symptoms, which include progressive muscle stiffness, continuous vibrating or twitching muscles, cramping, increased sweating, and delayed muscle relaxation, occur even during sleep or when patients are under general anesthesia. Many patients develop weakened reflexes and muscle pain, but numbness is relatively uncommon. Although symptoms can be limited to cranial muscles, in most patients stiffness is most prominent in limb and trunk muscles. Speech and breathing may be affected if pharyngeal or laryngeal muscles are involved.[1] Smooth muscles and cardiac (heart) muscles typically are spared. Sensory symptoms are rarely present.[2] Age of onset is between ages 15 and 60, with most patients experiencing symptoms before age 40.[1]
  • Last Reviewed: 5/12/2008

  • How might Isaac's syndrome be treated?
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  • Anticonvulsants, including phenytoin and carbamazepine, lamotrigine, and sodium valproate may be prescribed for treatment of Isaac's syndrome and can be used in combination.[1][2][4] These treatments usually provide significant relief from the stiffness, muscle spasms, and pain associated with Isaac's syndrome. In patients whose symptoms are debilitating or refractory to symptomatic therapy, immunomodulatory therapies may be tried.[4] Plasma exchange may provide short-term relief for patients with some forms of the acquired disorder.[1][4] Clinical improvement lasts about 6 weeks.[4]

    Single case studies suggest that intravenous infusions of immunoglobulins (IvIg therapy) can also help. However there are no good trials of long-term oral immunosuppression. Prednisolone, with or without azathioprine or methotrexate, has been reported as useful in selected patients.[4]


  • Last Reviewed: 5/12/2008

  • What is the prognosis for individuals with Isaac' syndrome? (Back to Top)

  • There is no cure for Isaac's syndrome. The long-term prognosis for individuals with the disorder is uncertain and depends on the underlying etiology (cause).[1][2]

  • Last Reviewed: 5/12/2008

  • Who can I contact to learn more about Isaac's sydrome?
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  • You can contact the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health (NIH), for information on Isaac's syndrome.

    NIH Neurological Institute
    PO Box 5801
    Bethesda, MD 20824
    Toll free:  800-352-9424
    Web site:   http://www.ninds.nih.gov/


  • Last Reviewed: 5/12/2008

  • How can I learn more about treatments used for Isaac's syndrome?
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  • You can find relevant journal articles on treatment used for Isaac's sydrome through a service called PubMed, a searchable database of medical literature. Information on finding an article and its title, authors, and publishing details is listed here.  Some articles are available as a complete document, while information on other studies is available as a summary abstract.  To obtain the full article, contact a medical/university library (or your local library for interlibrary loan), or order it online using the following link. Using 'Isaacs syndrome AND treatment' as your search term should locate articles. To narrow your search, click on the “Limits” tab under the search box and specify your criteria for locating more relevant articles.  Click here to view a search.
    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed
  • Last Reviewed: 5/12/2008


References  (Back)
  1. NINDS Isaac's Syndrome Information Page. National Institute of Neurological Disorders and Stroke (NINDS). January 14, 2008 Available at: http://www.ninds.nih.gov/disorders/isaacs_syndrome/isaacs_syndrome.htm. Accessed May 12, 2008.
  2. Suying Song. Myokymia. eMedicine . January 10, 2007 Available at: http://www.emedicine.com/neuro/topic235.htm. Accessed May 12, 2008.
  3. Jess G. Thoene, ed.. Physicians' Guide To Rare Diseases, 2nd edition. In: . Isaacs Syndrome. Montvale, NJ:Dowden Publishing Company; 1995:
  4. Skeie, G., et al.. Guidelines for the treatment of autoimmune neuromuscular transmission disorders. European Journal of Neurology . 2006.

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