You have always admired your dog's facial features, but now that your dog's skull is caving in, you are concerned something sinister may be going on. At a closer look, it's as if the dog's muscle has atrophied and has become somewhat concave. The skull may be caving in on only one side or perhaps both sides may be affected. Some dog owners may chalk it up to the dog getting older or skinny, and since most dogs seem to act normal despite the indentation, they may skip seeing the vet for some time. However, in most cases, a dog's skull that is caving in is something that requires medical attention.
A Closer Insight
Your dog's lovely facial features are the result of several muscles and nerves supplying the head area. When all works well, your dog has muscle tone and his nerves are effective in relaying information from the brain to the muscles of the head. Several muscles in the dog's head area include the temporalis muscle, the masseter muscle, the pterygoid muscle and the rostral digastricus muscles.
When it comes to the dog's nervous system instead, consider that there are twelve cranial nerves that serve the dog's facial area, allowing dogs to control the muscles of their eyes, ears, nose and jaw.
In particular, the dog's trigeminal nerve (also known as cranial nerve 5) controls the muscles of the jaw, and the sensory nerves to the mouth and nose. This is often a nerve affected when dogs develop a caved in skull.
Masticatory Myositis in Dogs
If your dog's skull appears to be caving in in both sides of the face, a possibility is a condition known as masticatory myositis. Masticatory myositis is not a common medical condition in dogs, but it tends to occur with more frequency in certain dogs breeds particularly pit bulls, Samoyeds, Doberman pinschers and Rottweilers.
Masticatory myositis stems from the immune system which happens to attack the certain muscle fibers (type 2M) located near the top of the head that help with chewing (hence the term masticatory, which means chewing). When the immune system attacks these muscle fibers, it causes inflammation.
Treatment consists of steroids (such as prednisone or dexamethasone) given orally for several weeks in an effort to suppress the immune system's reaction. The earlier that treatment is initiated, the better. Delays in treatment may lead to the formation of scar tissue which can put a dent in the muscles's ability to heal.
A Nerve Problem
If your dog's skull is caving in only on one side, there are chances that your dog may be suffering from some sort of nerve problem. Because nerves help a dog's facial muscles to work, any problem affecting the dog's nerves can end up causing muscle atrophy with its associate "caving in" appearance.
There are several potential causes that can affect the dog's nerves in the face. For example, inflammation of the dog's trigeminal nerve may lead to the nerve not working as it should. At times, an injury can do this, so if your dog has lately been exposed to some traumatic injury, this can be the culprit.
A tumor may also be a culprit. A trigeminal nerve sheath tumor may press on a dog's facial nerve cause a caving in appearance of the face on the affected side. Another tumor that may press on the facial nerves includes lymphoma, but by far, the most likely trigger, especially in a geriatric dog, is a tumor affecting the dog's trigeminal nerve, explains veterinarian Dr. Laura Devlin.
"There are few conditions that cause unilateral masseter and temporalis muscle atrophy. By far the most common is a nerve sheath tumor of cranial nerve 5 (trigeminal nerve)."~Dr. Laura Devlin
At the Vet's Office
Your vet will conduct a throughout examination, particularly focusing on your dog's muscle and nerve functionality. The vet may also decide to perform a tear test that checks the eyes' ability to produce tears, considering that when the dog's trigeminal nerve is impaired, tear production may be affected as well causing dry eye (keratoconjunctivitis sicca).
The vet may decide to have blood work done and if the vet suspects cancer, he or she may also request chest x-rays to rule out spread of cancer to the lungs. An MRI or CT scan can also be insightful for diagnostic purposes so to rule out cancer. A biopsy tissue sample of the affected muscles may be diagnostic for masticatory myositis.
Treatment depends on the underlying cause. Masticatory myositis requires steroids, while nerve sheath tumors or other tumors may need possible surgery or chemotherapy. Dogs with cancer affecting the trigeminal nerve jave a life expectancy anywhere from 5 to 21 months, points out veterinarian Dr. Ann M.
Challenging cases may require a referral to a board-certified veterinary neurologist. These veterinarians have made neurological issues their area of specialty and they can be normally found working at colleges of veterinary medicine or at private referral centers.
- J Am Anim Hosp Assoc. 1998 Jan-Feb;34(1):19-25.Clinical features of trigeminal nerve-sheath tumor in 10 dogs. Bagley RS1, Wheeler SJ, Klopp L, Sorjonen DC, Thomas WB, Wilkens BE, Gavin PR, Dennis R
- Masticatory Muscle Myositis in a Rottweiler dog. Kalumet, by permission of the owner, Creative CommonsAttribution 2.5 Generic license.
- Animal anatomical engraving Wilhelm Ellenberger and Hermann Baum: Handbuch der Anatomie der Tiere für Künstler In: University of Wisconsin Digital Collections Hermann Dittrich, illustrator. Public Domain