Facial Nerve Paresis/Paralysis in Rabbits

 

Facial nerve paresis and paralysis is a disorder of the facial cranial nerve — a nerve that originates in the brain (as opposed to the spine). Malfunction of this nerve can result in paralysis or weakness of the muscles of the ears, eyelids, lips, and nostrils. Moroever, an inability to move the eyes and facial muscles may result in a decreased secretion of tears, leading to additional pathology of the eyes.

 

In rabbits, facial nerve paralysis sometimes occurs after a dental or ear infection. Dwarf breeds and lop ear breeds tend to be at increased risk of developing facial nerve paresis and paralysis.

 

Symptoms and Types

 

Findings associated with ear disease

• Head tilting
• Ear and lip drooping
• Pain (especially when opening the mouth)
• White, dull, opaque, and bulging tissue within ear
• History of ear infections, especially vestibular (or inner ear) infections

Other symptoms

• Excessive drooling
• Food falling from the side of mouth
• Facial asymmetry (i.e., face appears lopsided or uneven)
• Rubbing of the eyes
• Cloudy cornea, eye discharge and redness
• Inability to close the eyelids symmetrically
• Collapse of nostril, nasal discharge
• Trouble walking or keeping balance (if nervous system is affected)

 

Causes

 

• Inflammatory — middle or outer ear infection, tooth abscesses, inflammation of the nerve directly due to bacterial infection
• Injury — fracture of the surrounding bones, or direct injury to the facial nerve
• Tumor — brain tumor
• Toxicity — botulism poisoning
• Unilateral or bilateral ear disease

 

Diagnosis

 

You will need to give your veterinarian a thorough history of your rabbit's health and onset of symptoms. There are several possible causes for this condition, so your veterinarian will most likely use differential diagnosis, a process that is guided by deeper inspection of the apparent outward symptoms, ruling out each of the more common causes until the correct disorder is settled upon and can be treated appropriately. Your doctor will begin by differentiating between one-sided and symmetrical disease, facial nerve paralysis from pure ear infection, and will also look for other neurological weaknesses.

 

X-rays of the ear and skull bones will be taken to look for masses or obvious swellings, while computed tomography (CT) can be used to allow for better visualization of the internal structure of the ears and skull. These visual diagnostic tools will identify the presence of a tumor. Standard laboratory tests include a complete blood profile, chemical blood profile, a complete blood count, and a urinalysis. Your veterinarian will be looking to identify the presence of an infection, and the type of infection, which may show up in the course of the blood and urine test analysis. More often, the blood and urine analyses are usually normal

 

If the symptoms appear to be neurological in origin, a sample of cerebrospinal fluid (CSF) can be taken for analysis, and can be helpful in detecting brainstem disease

 

Treatment

 

Rabbits are usually seen on an outpatient basis, but inpatient hospitalization may be required for the initial diagnoses and evaluations, or if your rabbit is severely ill. Depending on your doctor's findings, surgery may be required. But treatment generally consists of flushing and cleansing the ear, or ears, with cleaning solution, swabbing with cotton swab, and vacuum suctioning any debris from the ear. Artificial tears may also be used to prevent the eyes from drying.

 

Living and Management

 

It is important that your rabbit continue to eat during and following treatment. Encourage oral fluid intake by offering fresh water, wetting leafy vegetables, or flavoring water with vegetable juice, and offer a large selection of fresh, moistened greens such as cilantro, romaine lettuce, parsley, carrot tops, dandelion greens, spinach, collard greens, and good-quality grass hay. Also, offer your rabbit its usual pelleted diet, as the initial goal is to get the rabbit to eat and to maintain its weight and nutritional status. If your rabbit refuses these foods, you will need to syringe feed a gruel mixture until it can eat again on its own. And unless your veterinarian has specifically advised it, do not feed your rabbit high-carbohydrate, high-fat nutritional supplements.

 

Discuss eye care with your veterinarian, since the eye on the affected side may need lubrication due to loss of tear production. Also, keep in mind that the other side can become affected as well. Monitor your rabbit, and report any changes to your veterinarian if they should occur.

 

If your rabbit is exhibiting severe head tilt, you will need to support its head in a suitable position to prevent choking. Muscle paralysis is usually permanent, but as muscle healing and thickening develops, a natural "tuck up" may occur that reduces the facial asymmetry (lopsidedness). Other than the change in outward appearance that this paralysis can cause, most rabbits are able to tolerate this nerve deficit and will adjust with little difficulty.