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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