Canine fifth nerve infection, known in the veterinary world as trigeminal neuritis, does not have a well-established cause. It is thought to be an autoimmune or inflammatory condition. Dogs with this condition often have a difficult time closing their mouth and swallowing.
What is Trigeminal Neuritis?
At the base of the brain, 12 pairs of nerves (one on each side of the head) are responsible for specific neurologic functions of the head and face. These nerves are known as cranial nerves and are numbered from 1 to 12, or I to XII. The trigeminal nerve is the fifth cranial nerve (V), and it controls the muscles used for chewing as well as sensibility (feeling) in the face.
According to Dr. Jerry Northington, a veterinarian with Metropolitan Veterinary Associates, the condition affects the fifth cranial nerve. Affected dogs may have difficulty closing their jaws and putting food into their mouths, and they may appear to have difficulty swallowing. Many of the dogs that are affected drool excessively. Sensation (the ability to feel touch) across the face, lip movement, and tongue strength may or may not be affected.
It is most common in dogs and less common in cats, and it affects pets in their middle to later years of life. The condition is usually idiopathic, which means there is no known cause, though jaw paralysis can also be caused by a distinct underlying disorder such as a fifth nerve infection.
Although symptoms vary on a case-by-case basis, the following are the most common symptoms with this condition:
- Excessive drooling
- Inability to close mouth
- Rapid onset of an open jaw
- Difficulty eating
- Infrequent blinking
- Lethargic behavior
Diagnosing a Fifth Nerve Infection
A veterinary diagnosis is made based on the findings of the examination and the elimination of other disorders affecting the trigeminal nerve. To find a cause, your veterinarian may recommend a comprehensive physical examination, routine laboratory testing, and x-rays.
To rule out other disorders, advanced brain imaging, such as magnetic resonance imaging (MRI) or computed tomography (CT scan), may be necessary. One of the most serious disease disorders that must be ruled out is rabies. To exclude other illness possibilities, your vet may perform bone marrow core biopsies and muscle biopsies.
Although glucocorticoid (steroid) therapy has been suggested, there is no convincing evidence of its effectiveness. In most cases, dogs recover in two to three weeks, whether they are treated or not. If the situation does not improve after three weeks, your vet may recommend steroids or immunosuppressive medicines.
Although there is no specific treatment for this condition, supportive care is critical. Since dogs with this ailment are unable to take in food and water on their own, the dog may require assistance with eating and drinking. According to Dr. David Brewer (DVM, DACVIM), if your dog can still eat on their own, your veterinarian is likely to recommend a raised food bowl to make it easier for the dog to reach. A water bottle, like the ones used for rodents, is also generally recommended to aid in maintaining fluids.
In some dogs, insertion of a feeding tube may be necessary to provide sufficient nutrition. Lubricating ointments may also be applied and recommended for the eyes if the dog does not blink frequently.
During the recuperation process, most dogs lose 10 to 15 percent of their body weight. Dehydration is rarely an issue as long as very wet feedings are maintained. The food should have a gruel-like consistency for added palatability and water content.
Be Sure to Go to Your Follow-Up Visits
Follow-up visits are normally recommended on a regular basis to check for improvements in clinical symptoms and to measure the dog's body weight and overall health. Your veterinarian may also recommend further testing if the condition is not improving.
The good news is, recovery from trigeminal neuropathy is likely. The majority of dogs restore nerve function in two to four weeks, although complete recovery can take months. Some dogs only recover partially, and trigeminal nerve function does not always return.
You can help your dog strengthen their jaw muscles after the condition has subsided and they can move their jaws normally again. Based on your dog's overall health and age, your veterinarian will offer exercises to help you do this.
Observe Closely and Contact Your Veterinarian if Necessary
Although this condition generally goes away on its own, it's still important to monitor your dog closely and watch for any changes. Journaling how your dog is feeling each day can assist in recognizing any progress or setbacks. Notify your veterinarian right away if you discover any new clinical symptoms in your dog.