Muscle Contraction Disease in Cats

Muscle contraction disease in cats is known to the veterinary world as “myoclonus”, a neurological disease of the muscles, causing repetitive and rhythmic muscular contractions of one or more groups of muscles. Myoclonus is thought to be caused by abnormal pacemaker activity in the neurons due to infections such as coronavirus meningoencephalitis. Myoclonus can also be congenital; present at the time of birth, causing hypertonicity (spasms) at an early age. The prognosis for congenital myoclonus is rather poor and veterinary consultation is advised for felines suspected of having myoclonus.

Muscle contraction disease in cats is a condition that causes the muscles to contract suddenly without the animal intending to move said muscle. You may notice this involuntary movement in your cat’s legs, abdomen, neck or head. The muscles may contract lengthwise or vertically on the cat’s body. If the disease is affecting the jaw, you may notice what is called a “chewing gum fit” where the rhythmic movements of the jaw resemble that of a person chewing a stick of gum. Certain medications and infections can cause muscle contraction disease, whereas other felines are simply born with the condition.

Symptoms of muscle contraction disease in cats are very clear. Cat owners will be able to visibly see the disease causing the muscles of their feline’s legs, abdomen, head, neck or jaw to contract. The muscle contractions of myoclonus are usually short-lived, lasting just a few seconds from the time they started. The involuntary, rhythmic contractions can cause the feline to become unsteady and she may stumble upon walking. It is not uncommon for muscle contraction disease to affect cats while they sleep, abruptly waking the feline. 

Types

• Nocturnal Myoclonus: Sleep induced involuntary muscle contractions.
• Congenital Myoclonus: The cat is born with involuntary muscle contractions and the spasms occur for no known reason. 
• Active Myoclonus: Involuntary muscle contractions are triggered by a cat’s movement or wanting to move. 
• Stimulus-sensitive myoclonus: Muscles contract due to light, noise, or touch. 

There is no one cause of muscle contraction disease, but rather a group of conditions believed to cause this disease. Viral infections, such as distemper, and bacterial infections affecting the brain, like meningitis, are thought to be the most common causes of myoclonus. Metabolic abnormalities, intoxications, cofactor deficiency, and lesions of the central nervous system have also been known to cause muscle contraction disease. Chemotherapy drugs, such as chlorambucil, used to treat leukemia are also believed to cause myoclonus in cats. Lastly, muscle contraction disease can also be congenital, a disease the feline was born with.

Your veterinarian will need to go over any past illnesses, injuries and surgical procedures your cat has had over the course of her entire lifetime. Reviewing her medical history will also help to pinpoint any medications that have been used on your feline that could have caused the muscle contractions. A physical examination, a blood test, and urinalysis will likely be a part of your cat’s diagnostic procedure, as these tests aid in pinpointing abnormalities. An MRI or CT scan is not uncommon in diagnosing muscle contraction disease cases, as the veterinarian will likely want to evaluate the brain. Your veterinarian may also want to evaluate the spinal fluid using a needle, a procedure also called a spinal tap. Infection of the spinal cord, such as meningitis, can be detected through evaluation of the spinal fluid.

The treatment plan for a cat with myoclonus varies from one case to another, as this disease can be caused by underlying health problems or for idiopathic reasons. Antibiotics are commonly prescribed to patients with bacterial infections causing the feline to display involuntary contractions, whereas viral infections are treated with fluid therapy, medicine to take a fever down and other supportive care. Anti-inflammatory medications may also be prescribed to those felines experiencing swelling on the brain or spinal cord. The most appropriate form of treatment cannot officially be established without the examination of a licensed veterinarian.

The prognosis for muscle contraction disease caused by an underlying infection or medication use is relatively good. The muscle contractions usually cease or become less frequent after a cat has received veterinary treatment. Felines born with the condition do not have the best long-term prognosis, as there is no definitive treatment or cure for the disease by itself. Your veterinarian may alter your cat’s diet and perhaps suggest supplementation. He or she may also recommend keeping your cat’s stress levels down to reduce the chance of active myoclonus from occurring.