Temporomandibular Joint Disorders in Cats

The temporomandibular joint (TMJ) in cats is where the temporal and mandible bones of the jaw meet to form the hinged part of the jaw. Disorders of the TMJ may range in severity. There are no breed, sex, or age predispositions for most TMJ disorders. Jaw locking that occurs as a result of congenital defect is more commonly diagnosed in brachycephalic breeds such as the Himalayan and Persian.

TMJ disorders may be very painful for your cat and can affect their eating habits significantly. Seek immediate veterinary attention as soon as you notice any of the following symptoms:

• Inability to close or open the mouth
• Part of the jaw shifting to the side
• Signs of muscle atrophy and other facial deformities
• Loss of appetite/unwillingness to eat or drink
• Weight loss
• Dehydration
• Drooling
• Pawing at the face
• Excessive meowing

Types 

There are several types of TMJ disorders in cats, including, but not limited to:

• Luxation or subluxation: This occurs when the joint becomes fully or partially dislocated.
• Open-mouth jaw locking: Jaw locking is typically caused by luxation or subluxation. Episodes of jaw locking may be random, and will typically occur more frequently if left untreated. Jaw locking can last anywhere from a few minutes to an hour.
• TMJ ankylosis: This disorder will render the cat unable to fully or partially open its mouth. Ankylosis is most commonly caused by trauma, infection, or disease.
• Masticatory muscle myositis: This is an inflammatory condition that affects the muscles the cat uses to chew food. Masticatory muscle myositis will cause those muscles to swell, creating difficulty in opening the mouth.
• Ear inflammation: In severe cases of ear inflammation – particularly those in which the ear canal is perforated – the disorder may affect the TMJ.
• Tympanic bulla neoplasia: Cancer of the middle ear is a very rare condition in most species, but can cause inflammation of the TMJ. Cats with this type of cancer may have a history of chronic ear infection.

The causes of TMJ disorders in cats depend on which type of disorder a cat is suffering from. Causes may include:

• Accidental trauma
• Congenital defect
• Cancer
• Infection
• Secondary disease

The causes of some conditions of the TMJ – notably masticatory muscle myositis – are not fully understood.

Your vet will first perform a thorough physical examination. You should let your vet know how long your cat has been experiencing any symptoms. X-rays are generally required in order to make a definitive diagnosis. CT scans may also be beneficial for diagnosing certain types of TMJ disorders. If cancer is suspected, cytology or biopsy may be performed to confirm the diagnosis.  Additional diagnostic testing may be recommended based on the suspected underlying cause.

Treatment will vary depending on the severity and type of TMJ disorder your cat is suffering from. Your vet will be able to advise you on a treatment plan based on your cat’s specific needs.

Conservative treatment can cure certain TMJ diseases, including luxation/subluxation, ear inflammation, and masticatory muscle myositis. Luxation/subluxation may be resolved quickly by manually manipulating the jaw back into place. Ear inflammation may be treated with antibiotics, anti-inflammatory drugs, or antihistamines.

Prednisone medications are typically prescribed in cats suffering from masticatory muscle myositis. Treatment may last from two months to eight months. Cancer of the middle ear may also be treated conservatively with several lymphotoxic drugs.

For cases of acute jaw locking, your cat may be anesthetized while your vet manually shifts the jaw back into place. However, there is a chance the locking can recur in the future whenever the cat opens its mouth wide. If your cat suffers from frequent jaw locking episodes, surgical removal of part of the zygomatic arch is generally the treatment of choice. Cancer of the inner ear may also be treated with surgery, radiation, and/or chemotherapy depending on owner and veterinary preferences.

Surgical correction may be required for ankylosis, recurrent luxation/subluxation of the TMJ, and severe cases of chronic ear infection.

Recovery and prognosis may vary depending on the severity and underlying cause of TMJ disorders. Your vet will provide you with comprehensive aftercare instructions following treatment.

If your cat has had surgery, ensure they have a warm, safe place to rest on the return home. Do not allow them to irritate the surgery site. If their jaw injury was the result of trauma, you may want to limit their outdoor activity.

Your vet may schedule follow-up appointments as needed to monitor the condition. Due to the nature of TMJ disorders, the likelihood of recurrence is generally high. If the condition recurs, contact your vet immediately.