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

Neuromuscular diseases

Polyneuropathies (widespread disease affecting multiple nerves)

Cancer

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

Excessive salivation

Dropping of food

Drooping of the ear in dogs with erect (upright) ear conformation

Slight deviation of the nose to one side

Head tilt

Asymmetric pupil size

Nystagmus (abnormal movement of the eyes)

Ataxia (uncoordinated gait)

Generalized weakness

Asymmetric appearance to the orbital fissures (one eye appears to be opened more widely than the other)

Diagnosis

History and physical exam

Complete blood count (CBC)

Biochemical profile

Otoscopic (ear) exam

Thyroid function evaluation

Schirmer tear test (evaluates tear production)

Ocular (eye) exam

Radiographs (X-rays)

CT Scan or Magnetic Resonance Imaging

Radiographs of the thorax (chest)

Electromyography (EMG)

CSF (cerebrospinal fluid) tap

Acetylcholine receptor antibody test

Treatment

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.