Temporomandibular Myositis in Dogs
Temporomandibular myositis, also known as masticatory myositis, is a condition which primarily affects the muscles of the temporomandibular, or jaw joint. According to Hungarovet, a site for Hungarian veterinary professionals, this condition is the second most common neuromuscular problem in dogs. It affects both large and small dogs, and is best treated early in its progression. If allowed to progress untreated, this condition could cause serious damage to the jaw muscles.
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Affected Animals
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According to the Michigan Veterinary Specialists website, German shepherds, retrievers and other large breeds are the most likely to develop temporomandibular myositis. Doberman pinschers may also get it. The disease strikes males and females about equally, and is most common in young to middle-aged animals. The disease occurs in both chronic and acute forms, which may make it harder for owners to tell that their dog has this problem.
Symptoms
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Masticatory myositis causes swelling in the muscles of the face and forehead. Dogs will have pain and difficulty opening the mouth, and may be reluctant to eat. Some will eat, but bolt their food instead of chewing. The eyes may bulge, due to pressure in the muscles around them, and the third eyelid may protrude. Dogs may have a fever and salivate excessively. Over time, the inflammation will cause the muscle tissue to scar, creating a sunken appearance around the cheeks and jaw and along the top of the head.
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Diagnosis
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Veterinarians diagnose this condition based on clinical signs, but must take steps to make sure that the problem is not another, similar disease. This may involve an electromyography (EMG) and blood tests. Definitive diagnosis requires a muscle biopsy. The vet should check the dog's health history, creatine kinase levels in the blood and perform an X-ray or CT scan of the skull and teeth. It may not be possible to open the dog's jaws while it is under anesthesia–this is a common indicator of masticatory myositis.
Treatment
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Treatment of masticatory myositis requires doses of immunosuppressive steroids, which prevent the dog's body from attacking its own jaw muscles. In some cases, additional drugs to suppress the immune system may be needed. During the first several months of therapy, the dog will need an examination every three to four weeks to make sure treatment is working. Dogs may require soft foods or a feeding tube to ensure proper nutrition, and should not have hard chew toys.
Expert Insight
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According to Hungarovet, the dog's immune system attacks only the chewing muscles because they contain a special type of muscle tissue. This tissue, called type 2M muscle fiber, occurs nowhere else in the body, and is served by a unique type of nerve branch. Currently, veterinarians do not know what causes the immune system to attack this specific type of muscle.
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References
- Photo Credit german shepherd image by Vaida from Fotolia.com
