Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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There are two  facial nerves - one on either side of the head, and they are one of the main nerves leaving the brain - in fact they are  called the VII cranial nerves, and are generally known as the nerves of "facial expression". 

On each side the facial nerve passes near to the ear and around the angle of the jaw (around the mandible) . It carries nerve messages to and from the ear, facial muscles, eyelids,  the salivary glands (which produce saliva in the mouth) and lachrymal glands (which produce tears). 

The facial nerve carries mixed nerve fibres including :

  • Motor neurones - stimulate action in tissues eg stimulate muscle to contract
  • Parasympathetic fibres - often stimulate non-life threatening secretions eg saliva, tears 

The cause of facial nerve paralysis is often unknown (called idiopathic facial paralysis) however, th
ere are several known causes as well including :

  • Injury - any blow or wound  to the nerve can cause paralysis
  • Local pressure on the nerve - eg an adjacent tumour
  • Injury to the nerve secondary to middle ear infection
  • Hypothyroidism
  • As a consequence of Lyme Disease

Breed Occurrence

Hypothyroidism, which can cause facial paralysis, is reported to be particularly prevalent in the following breeds of dog : Akita, Boxer, Cocker Spaniel (American), Collie, Doberman Pinscher, English Setter, German Shepherd Dog, Golden Retriever, Irish Setter, Labrador Retriever, Old English Sheepdog,  Shetland Sheepdog. However, autoimmune thyroiditis  - one of the most common causes of hypothyroidism is now thought to be an inherited problem in about 50 breeds !

Lyme Disease - is a transmitted by deer ticks, and so it is most common in working field dogs and dogs exercised in countryside  frequented by deer.


The signs of facial nerve paralysis are predictable from a knowledge of the type of nerve fibre it consists of, and the anatomical areas it serves. Paralysis usually only occurs on one side of the face resulting in  :

If the facial paralysis is secondary to another disease, signs of that disease might also be present in the same patient eg hypothyroidism, Lyme Disease, ear infection.

Complications of facial nerve paralysis can be serious, though they usually affect only one side including :

  • "Dry eye" due to the lack of tears leading to inflammation of the surface of the eye (the cornea) called keratitis.  If this is not corrected ulceration of the cornea may occur
  • An inability to blink means that debris including small bits of  foreign material are not cleared away from the surface of the eye - again resulting in injury to the cornea
  • Lack of saliva leads to dryness of the mouth which may impair eating. However, as the paralysis usually only affects one side, the other salivary glands are probably functioning normally and so lubricate the mouth.
  • Paralysis of the facial muscles may lead to difficulty eating (dysphagia)

Visual examination of the animal by a veterinarian is usually sufficient to diagnose the presence of facial nerve paralysis. 

Diagnostic tests may be needed to confirm the diagnosis of other diseases such as hypothyroidism or Lyme Disease.

 Facial paralysis may be temporary or permanent. It is most likely to be permanent if the nerve has been transected, has degenerated or if there is a primary brain lesion.

Blunt trauma usually causes only temporary paralysis and if the underlying cause is known and treatable eg Lyme Disease, ear infection  or hypothyroidism - the patient can be expected to recover in most cases.


Good for most patients

Long term problems
Permanent paralysis can lead to the complication of dry eye and corneal ulcers as mentioned above.


Updated January 2016