What is idiopathic facial nerve paralysis and what are the causes?
Facial nerve paralysis describes the dysfunction of the facial nerve leading to paralysis of the muscles of the face. The facial nerve originates from the brainstem runs through the middle ear and innervates all the muscles of the face except the ones needed for chewing. The term idiopathic means of unknown cause. Therefore, all the tests performed aim at ruling out other causes (disease of the brain or in the middle ear). A similar condition is recognised in human medicine and is called Bell’s Palsy.
Which pets typically get facial nerve paralysis?
Pets of any age and breed can develop idiopathic facial nerve paralysis but it is seen more commonly in middle aged to older particularly middle pets.
What are the signs of idiopathic facial nerve paralysis?
A pet with facial paralysis has a ‘dropped’ appearance to the face on one side (similar to a person that has a stroke). One ear is lower than the other and the lip hangs down on the affected side. You will often see that the dogs are unable to blink and dribble saliva and drop food from the affected side. Rarely this disease can affect both sides of the face and sometimes dogs will be diagnosed with idiopathic facial nerve paralysis and vestibular syndrome.
How is idiopathic facial nerve paralysis diagnosed?
Idiopathic facial nerve paralysis is a ‘diagnosis of exclusion’, meaning that diagnostics are directed at ruling out other (potentially more serious) causes of facial nerve paralysis. We would typically recommend and MRI scan of the brain and middle ears and in some cases cerebrospinal fluid (CSF) analysis. We will usually take bloods as well to check for endocrine disorders which can predispose to idiopathic facial nerve paralysis. If all these tests are normal a diagnosis of idiopathic facial nerve paralysis can be made.
What treatment options are available?
There are no treatments for idiopathic facial nerve paralysis but it is important to strictly monitor the affected eye and if needed to apply eye drops to avoid secondary eye problems from drying out and a lack of the blink reflex.
What is the prognosis?
The described signs can recover completely over the following weeks but often only recover partially or are permanent. This will rarely have a significant effect on your dog’s quality of life. After a couple of weeks, the early signs (as described above) are replaced by the ‘chronic’ signs. The droopy lip will contract and the nose will sometimes start to deviate slightly towards the affected side. Your pet will still be unable to move their lip or blink with the eye.