Diagnosis

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.

Causes

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.