Inflamed Chewing Muscles in Cats

Inflammation in the masticatory, or chewing, muscles in cats can occur in any breed of cat at any age. The exact cause of this condition is not known, however, it is thought to be caused by an autoimmune response in the body. If your cat suffers from inflamed chewing muscles, it is important to see your veterinarian for advice. 

Cats can suffer a variety of medical conditions that affect their muscles. While it is not common, some cats develop pain and inflammation in the muscles of the jaw. This results in difficulty chewing and eating.

Cats typically suffer from two types of facial myositis, or muscle inflammation. One type, masticatory myositis,  affects the muscles surrounding the eye. If cats are affected by masticatory myositis, the jaw muscles are involved. The most common symptoms associated with the disorder include:

• Difficulty moving the jaw
• Swollen jaw muscles
• Pain in the jaw, especially when chewing
• Trouble moving the jaw to get food in the mouth
• Weight loss
• Loss of appetite
• Atrophy of the jaw muscles

While the exact cause of masticatory myositis is unknown, it thought to be caused by an autoimmune response in the body. This can be a reaction caused by:

• A variety of viruses
• Certain types of bacteria
• The presence of a foreign body
• A response to the cat's own body cells

In order to diagnose masticatory myositis in cats, veterinarians begin by asking owners important questions regarding their cat's health history. Any information regarding problems at birth, pre-existing conditions and when symptoms first began should be provided. After taking a full medical history, doctors take and record the cat's vital signs. This includes weight, temperature, heart rate and respiration rate. A blood draw will be performed for a complete blood count and full chemical profile. A urinalysis will also be done to check for signs of urinary tract infection and protein in the urine. Once these tasks are accomplished, the doctor will examine the cat to check for signs of illness or the presence of a foreign body. 

After the physical examination, doctors often perform diagnostic tests to determine the cause of illness and to rule out serious medical conditions. A series of X-rays of the head will give the doctor a view of the face. An MRI may also be done for signs of inflammation in the masticatory muscles. In severe cases, doctors may use electromyography to evaluate electrical activity within the cat's chewing muscles. Doctors may also perform surgery to obtain a biopsy of the temporalis muscle, to look for fibrosis and signs of muscle wasting. 

The treatment for immune-mediated diseases is aimed at reducing the inflammation in the body causing the pain and swelling. This is done by prescribing a classification of drugs known as immunosuppressives. These medicines work by bringing down inflammation, which has a calming effect on the muscles. Steroids such as prednisolone are the most commonly prescribed drugs for this purpose. Other medications, such as cyclosporine and cytarabine, may also be used to treat cats with this condition. To treat inflammation of the chewing muscles, these drugs are given in high doses and tapered down once symptoms are reduced. Cats that have a severe form of this condition and cannot eat may need to be placed on soft food or have a feeding tube in place to control weight loss. 

Since using immunosuppressive medications can cause complications with long term use, veterinarians prescribe them for short periods of time if possible. Giving cats these medications for long periods of time can weaken their immune system, placing them at an increased risk of infection and illness. If your cat is taking immunosuppressive medicine, be sure to follow the orders of your doctor when giving this medicine. Never alter the dosage without speaking to your doctor, as this could cause serious health problems. Since your cat could become sick more easily on immunosuppressive medication, it is usually best to keep your cat isolated from other animals until he finishes the medicine.

Cats with masticatory myositis may be successfully treated with medication and diet modification. However, cats that have severe muscle wasting of the jaw may not have a good prognosis over the long term. For this reason, it is important to treat conditions that cause inflammation of the jaw muscles as quickly as possible. Prompt treatment is the best way to prevent muscle damage which leads to complications later on. Veterinarians typically continue to monitor cats with this condition for several months after diagnosis, to be sure the prescribed treatment is working and the symptoms are not worsening.