Pet Education
 

Facial Paralysis: What a droopy face could mean for your pet

Facial Parlayisis in Dogs

By Bonnie Oliphant, DVM
Practice limited to Neurology

Facial paralysis is a condition associated with drooping of the face including lip and eyelid – most commonly on one side (unilateral) but can affect both sides in some cases.

The signs can come on suddenly or gradually. Facial paralysis can be complete with inability to move the face at all or partial with decreased movement in the face. If there is still some movement of the lip/eyelid then this weakness is called facial paresis. There are many possible causes for facial paresis/paralysis. A complete neurologic examination and some additional tests can help to determine the cause. Treating any underlying cause is important however signs of facial paralysis may persist even with appropriate treatment.

Facial nerve (cranial nerve VII)

The facial nerve (also known as cranial nerve VII) is the nerve responsible for innervating the muscles of facial expression including the muscles that allow the eye to blink (orbicularis oculi muscles). It is one of twelve paired cranial nerves. There are two facial nerves in each dog – one on each side, left and right. The nerve originates in the brainstem and travels through the skull. It travels very close to the middle/inner ear while traveling inside the skull, along with another cranial nerve – the vestibulocochlear nerve (cranial nerve VIII) which is responsible for balance/hearing. After exiting the skull, the facial nerve branches to supply the muscles of facial expression.

The facial nerve has another important job – to innervate the glands that produce tears (lacrimal glands), saliva (mandibular/sublingual salivary glands) and that keep the nose moist (lateral nasal gland). The facial nerve also carries sensory information – sensation to the inside of the ears (pinna) and most of the tongue (the tip and middle).

Dysfunction of the facial nerve

If the facial nerve is not able to do its job properly, then the face can become droopy/slack on the affected side. The facial nerve can be affected at the level of the brainstem, or the peripheral nerve can be affected inside/outside the skull. A common location for disease that can affect the facial nerve is the middle/inner ear because the facial nerve travels very close to this area inside the skull.

Signs to watch for in cases of facial paresis/paralysis

Signs are often seen on only one side of the face, less commonly both sides of the face may be affected:

  • Drooping of the lip (best observed when your dog is panting)
  • Widening of the opening of the eye (palpebral fissure)
  • Inability to blink/close the eye – can be easier to appreciate when the pet is relaxed/sleeping
  • Drooling out of one side of the mouth
  • Dropping food out of one side of the mouth
  • Increased discharge from the eye
  • Crusting of the nostril on the affected side (xeromycteria)
  • Deviation of the nose to one side
  • Sometimes drooping of the ear on the affected side
  • Increased movement/flicking of the third eyelid

Other conditions that can occur along with facial paralysis

Vestibular dysfunction: Problem with the balance system/vestibulocochlear nerve/cranial nerve VIII

  • Head tilt
  • Rapid jerking eye movements (nystagmus)
  • Stumbling/falling/circling/leaning to one side (vestibular ataxia)

Horner’s Syndrome: Dysfunction of the sympathetic nerve supply to the eye

  • Small pupil (miosis)
  • Prominent/protruded third eyelid
  • Sunken appearance to the eye (enophthalmos)
  • Drooping eyelid (ptosis)

Possible causes for facial paresis/paralysis

The most common cause for facial paralysis in dogs is idiopathic, meaning unknown cause. Idiopathic facial paralysis can occur suddenly. Clinical signs are typically most severe/apparent early on within the first 1-2 weeks. They may improve over time – several weeks to months – however some permanent changes may occur. Over time, the facial muscles can contract and the nose may deviate to one side.

With idiopathic facial paralysis, there are typically no other neurologic deficits although occasionally vestibular dysfunction can occur at the same time (head tilt, rapid eye movements, leaning/falling/circling to one side). There is no known treatment for idiopathic facial paralysis other than supportive care with artificial tears to prevent dryness of the cornea (surface of the eye) which can lead to ulceration of the eye and sometimes secondary infections.

It is very important to rule out other possible causes for facial paralysis because they are more serious and can require additional treatment. Other possible causes for facial paralysis involving the peripheral nerve may include middle/inner ear infection (otitis media/interna), low thyroid hormone (hypothyroidism), an autoimmune condition called myasthenia gravis, recent trauma/surgery to the face/middle ear, diseases affecting multiple peripheral nerves, and cancer of the nerve or middle ear. If the brainstem is affected, then possible causes may include inflammation of the brain (encephalitis – autoimmune or infectious), stroke or cancer.

What to do if you think your pet has facial paresis/paralysis

The most important thing to do is schedule an appointment with your veterinarian for a thorough physical examination. Tests that you may see them perform include testing for a blink reflex (palpebral reflex), menace response (making a menacing gesture towards the eye), looking into the ear to look for signs of infection/whether the ear drum is intact (otoscopic examination), testing tear production (Schirmer tear test) and putting bright orange Fluorescein stain into the eye to assess for corneal ulceration. Your veterinarian may recommend additional testing such as blood work including thyroid hormone testing. They may also recommend referral to a veterinary neurologist to help assess your pet for underlying conditions other than idiopathic facial paralysis.

Veterinary neurologists will perform a full neurologic examination to assess whether other parts of the nervous system are affected and whether the problem seems to be at the level of the brainstem or peripheral nerve/middle ear. Advanced imaging with MRI of the head can be used to assess the facial nerve – both the middle/inner ears and the brainstem can be evaluated in the same study. Electrodiagnostic testing (electromyography or EMG) may also be considered to rule out a condition affecting multiple peripheral nerves. Sometimes a spinal tap and fluid analysis or further assessment of the middle/inner ears is performed (myringotomy and culture) depending on the results of the MRI. These tests require general anesthesia.

Treatment/Prognosis

Idiopathic facial paralysis has an overall good long-term prognosis although facial nerve function may never return to 100% normal. Again, there is no specific treatment for idiopathic facial paralysis. Sometimes artificial tear supplementation is required long-term to prevent dry eye related corneal ulcers. Pets can typically function well to eat and drink although they may have more messy eating habits, especially early on.

The prognosis for other causes for facial paralysis is variable – if the underlying condition can be treated appropriately, then the facial paralysis may improve and most importantly other clinical signs may be prevented with appropriate treatment. Treatment for a middle/inner ear infection typically involves a long course of oral antibiotics and sometimes topical ear treatments. In some cases, surgery is needed to fully clear the infection. Treatment for hypothyroidism involves oral thyroid hormone supplementation.

What can you do at home?

Keep a close eye on your pets face (not a hard task – they are pretty cute and most of the time they won’t let you forget what they look like!) and if you notice any asymmetry or difficulty blinking/eating, have them evaluated by your veterinarian. It can help to compare their current facial expression to one in photos you may have from previous months or years.

Facial Parlayisis in Dogs


Animal Specialty Group

DVM, Practice Limited to Neurology

Dr. Bonnie Oliphant received her B.S. in Zoology from the University of Calgary, and then earned her DVM from the Western College of Veterinary Medicine at the University of Saskatchewan in Saskatoon, Canada. She complemented internships in Toronto, Canada and Leesburg, VA and her residency at the University of Wisconsin.