Muscle Contraction Disease (Myoclonus) in Cats


PetMD Editorial

Published Feb. 15, 2010

Myoclonus in Cats


Myoclonus is a condition in which a portion of a muscle, entire muscle, or group of muscles contracts in a coarse, repetitive, involuntary, and rhythmic manner at rates up to 60 times per minute (sometimes even occurring during sleep). These abnormal contractions occur due to nervous dysfunction and most commonly affect groups of muscles involved in chewing and/or any of the skeletal muscles of the limbs.


Myoclonus is rarely seen in cats and is more common in dogs.


Symptoms and Types


Involuntary, continuous, coarse, and rhythmic contractions of a muscle, portion of a muscle, or group of muscles is the most common sign to look out for. However, there are other symptoms your cat displays that are related to the underlying disease causing myoclonus.




  • Congenital
  • Due to infections
  • Drug-induced (e.g., chlorambucil)




You will need to give a thorough history of your cat’s health, including any illnesses it may have recently suffered from and symptoms it has displayed. The veterinarian will then conduct a complete physical examination as well as a complete blood count (CBC), biochemistry profile, and urinalysis -- the results of which may show abnormalities related to underlying cause, including inflammation of brain and spinal cord (encephalomyelitis). He or she may also take a sample of your cat's cerebrospinal fluid (a protective and nourishing fluid circulate around brain and spinal cord) or administer an MRI (Magnetic Resonance Imaging) on the animal.



The course of treatment for myoclonus will depend on the underlying cause of the disorder. Cats with inflammation of brain and spinal cord, for example, are given medication to reduce swelling.


Living and Management


This problem usually continues indefinitely, although remission is possible. Watch for symptoms that may be associated to the treatment for brain and spinal cord inflammation, and call your veterinarian if they should worsen. The cat may require a new diet or movement restriction depending on the severity of the disease.

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