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Facial Nerve Paralysis

Issue Description
Facial nerve paralysis is a common problem that involves the paralysis of any structures innervated by the facial nerve. The pathway of the facial nerve is long and relatively convoluted, and so there are a number of causes that may result in facial nerve paralysis.

In most dogs, facial paralysis is not associated with disease of the brain, but rather with direct damage to the nerve that controls the muscles in the face (facial nerve). This nerve comes from the back of the brain to control the muscles of facial expression (ears, lips, eyelids and nostril).

The most common cause of facial nerve paralysis in dogs is idiopathic facial nerve paralysis. The term idiopathic means that there is no known cause. Therefore in idiopathic disease all the tests results will be normal. A similar condition is recognised in human medicine as Bell's Palsy.

The second most common cause of facial nerve paralysis is a deep- seated infection of the ear (otitis media/interna). In this case other signs such as Horner's syndrome (decreased pupil size and third eyelid coming across the eye) and/or vestibular syndrome (head tilted to one side, and balance loss) are frequently seen in addition to facial paralysis. Rarely, facial paralysis can be associated with disease affecting multiple nerves (polyneuropathy) or brain disease (tumour, infection or inflammation). In these cases, other neurological signs are usually observed in addition to facial paralysis.

A dog with facial paralysis has a dropped appearance to the face on one side. One ear is held lower than the other and the lip hangs down on the affected side. Affected dogs are unable to blink and have a tendency to dribble saliva and drop food from the side of the mouth. Occasionally, the same signs may be present on both sides of the face which can make the changes difficult to recognize.

Your vet will first want to perform a thorough ear examination to detect signs of ear infection. If this examination is normal then the deeper parts of the ear and brain may be examined using specialised imaging techniques. The deeper part of the ear can be seen on X-Rays of the skull and the back of the brain can be examined using CT or MRI scans. In some cases it may be necessary to take a sample of fluid from around the brain to check for signs of inflammation.

Idiopathic facial nerve paralysis is usually left untreated because, by definition, no cause has been identified. Facial nerve paralysis secondary to otitis requires at least 4 to 6 weeks oral antibiotic. Cases that are unresponsive to medical treatment may require surgical drainage.

Although, the signs are often permanent (even when an underlying cause is identified and adequately treated) this will rarely have any significant effects on your dog's quality of life. If there is no underlying cause of the nerve damage the outlook is good. After a couple of weeks the early signs (dribbling of saliva, dropping of food and a floppy lip) are replaced by the 'chronic' signs. The droopy lip will start to contract so that it regains its normal size and shape - although the animal will remain unable to move their lip. On rare occasions, the other side of the face may also drop at a later date.

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