Facial nerve paresis (weakness) or paralysis (total dysfunction) is an abnormality of the facial nerve (7th cranial nerve), resulting in improper function or paralysis of the muscles associated with facial expression. These include the muscles of the ears, lips, eyelids and nose.
In many cases the cause of facial nerve paralysis is idiopathic (unknown). The most commonly identified disease process causing facial nerve paralysis is otitis media-interna
(inflammation of the inner and middle ear). Less common, but possible, causes of facial nerve paralysis include: Trauma
Surgery of the ear or surrounding structures
Polyneuropathies (widespread disease affecting multiple nerves)
Primary inflammatory diseases of the central nervous system
Facial nerve paralysis occurs in both cats and dogs, but is more common in dogs. Breeds at an increased risk for this disorder include the cocker spaniel, Pembroke Welsh corgi, boxer and English setter. It occurs in adult animals, usually greater than five years of age. There is no apparent gender predilection.
Clinical signs may vary, depending on the underlying cause of the facial nerve paralysis. Usually signs are unilateral (involving one side of the face) but they may be bilateral (involving both sides).
What to Watch For
An inability to blink
Eye discharge or irritation
Drooping of the lip
Dropping of food
Drooping of the ear in dogs with erect (upright) ear conformation
Slight deviation of the nose to one side
Asymmetric pupil size
Nystagmus (abnormal movement of the eyes)
Ataxia (uncoordinated gait)
Asymmetric appearance to the orbital fissures (one eye appears to be opened more widely than the other)
History and physical exam
Complete blood count (CBC)
Otoscopic (ear) exam
Thyroid function evaluation
Schirmer tear test (evaluates tear production)
Ocular (eye) exam
CT Scan or Magnetic Resonance Imaging
Radiographs of the thorax (chest)
CSF (cerebrospinal fluid) tap
Acetylcholine receptor antibody test
There is no specific treatment for facial nerve paralysis. Any underlying disease should be treated. Animals may need to be medicated with eye lubricants to avoid corneal damage. If keratitis (inflammation of the cornea) or corneal ulcers (defects in the cornea) are identified, they must be treated with appropriate ophthalmic antibiotics.
Home Care and Prevention
Application of ophthalmic medications as directed by your veterinarian is important to avoid ocular complications. Follow-up exams with the veterinarian are recommended to evaluate signs of progression or resolution and to maintain close observations of any ocular problems.
For most cases, there is no specific care to reduce the risk of facial nerve paralysis. However, since this is often associated with middle and inner ear disease, it is important to maintain good ear care, especially in animals predisposed to ear disease such as cocker spaniels. This includes careful ear cleaning and immediate veterinary treatment of all ear infections.