other name: Bell’s Palsy
Overview
There are twelve pairs of cranial nerves, each with its own distinct function. The seventh cranial nerve, known as the facial nerve, is responsible for controlling the muscles involved in facial expression. It sends signals to the muscles that move the ears, lips, eyelids, and nostrils.
Facial paralysis occurs when one or both sides of the face becomes droopy or less responsive. This isn’t due to damage to the muscles themselves, but rather to a problem with the facial nerve that supplies them. When the nerve is affected, the muscles don’t receive the signals they need, resulting in loss of movement on the affected side.
Causes
The most common cause of facial nerve paralysis in dogs is idiopathic facial nerve paralysis, which means the exact cause is unknown. While there may be an immune-mediated component to this disease, corticosteroids typically do not reduce the duration or severity of symptoms.
The second most common cause is a middle or inner ear infection. Uncommon causes of facial nerve paralysis include inflammation or infection of the nerve, tumors, or certain metabolic conditions.
Clinical Signs
An animal with facial paralysis will typically have a droopy appearance of the face and be unable to blink or move the facial muscles. Despite having a good appetite, they often drool more than usual or drop food from the mouth because they can’t control the muscles properly.
Because of this close connection with other facial nerves, some animals with facial paralysis may also show other neurological signs, such as a head tilt or coordination issues.
Diagnosis
To better understand what’s causing the facial nerve paralysis, the most important diagnostic tool is an MRI. Based on the MRI findings, additional tests such as a spinal tap, thyroid panel, or infectious disease testing may be recommended.
If all test results come back normal and no underlying condition is found, a diagnosis of idiopathic facial nerve paralysis is made by ruling out other possible causes.
Treatment
Treatment for idiopathic facial paralysis in dogs is focused on supportive care, as most improve spontaneously. An important aspect of treatment is protecting the eyes. Because affected dogs often cannot blink properly, they are at increased risk for dry eye, corneal ulcers, and other eye injuries.
To keep the eye healthy use lubricating eye drops such as artificial tears several times a day, especially when windy or smoky. If there is evidence of an eye infection, these conditions must be treated promptly with appropriate topical ophthalmic antibiotics to prevent further damage.
There is currently no proven medication that speeds up nerve recovery in idiopathic cases. Although the benefits are uncertain, a short course of corticosteroids may be considered in some situations.
Prognosis
Recovery from idiopathic facial paralysis can vary between animals, but most pets make some degree of recovery. Some pets fully recover within a few weeks to months, while others may experience lifelong partial weakness. Fortunately, most dogs and cats adapt well and can continue to enjoy a good quality of life, even if the facial weakness does not completely resolve.