A facial nerve originates in the brain and controls the muscles on one side of the face. There are two facial nerves, one for each side of the face. The facial nerve travels in and around the structures of the middle ear and along the jawbone to enter the parotid gland (one of the salivary glands) before the ear. Within the parotid gland, the facial nerve divides into five branches that control the various muscles and glands of the head and neck. It controls facial expressions while crying, frowning, smiling, or winking. Facial nerve damage can be repaired in many cases. The success rate depends on the extent and the duration of the nerve damage. The sooner it is identified and treated appropriately, the better the prognosis.
Facial nerve damage may result in facial muscle twitching, weakness, or paralysis. The signs and symptoms of facial nerve damage include:
Watering of the eye on the affected side
Inability to close the eye completely on the affected side, leading to dryness
Dryness of the mouth
Change in taste perception
Deviation of the mouth to the unaffected side
Loss of wrinkling of the forehead on the affected side
Loss of nasolabial fold (smile lines) on the affected side
Dribbling of saliva
Common causes of facial nerve disorder include:
Trauma: Babies may suffer from trauma during difficult labor. The nerve may also get damaged during a skull fracture, injury to the face or ear during a surgical procedure, etc.
Nervous system disorders like a stroke
Infection of the ear or face, especially herpes
Tumors of the brain and nerve
Toxins (carbon monoxide poisoning)
Bell palsy: Also called idiopathic facial nerve paralysis. The exact cause is not known. It is sudden in onset and could be due to diabetes, pregnancy, or sudden cold wind against the side of the face. In most cases, there is no identifiable risk factor.
Many instances of facial nerve damage get better on their own. This includes damage due to Bell palsy, infection, and toxins. Damage due to trauma can be also repaired in many cases. Most patients should have some recovery within the first 2-4 weeks with medications like oral or intravenous steroids and physical therapy. Complete recovery may take up to 6 months. There are surgical options to repair facial nerve damage if conservative treatments don’t work. These include:
Decompression: The nerve may be compressed by swelling (edema), hematoma (blood clot), or a fracture in the skull. The bony canal surrounding the facial nerve is drilled and the nerve is exposed. The sheath around the facial nerve is also slit to relieve the pressure applied to the nerve due to swelling or blood clots.
End to end anastomosis: This is done when the facial nerve is cut (severed) and the gap between the severed ends of the nerves is only a few millimeters. The two ends of the nerve are sewed end to end.
Nerve graft or cable graft: This is done when the gap between severed ends cannot be closed by an end-to-end anastomosis. A nerve graft is more suitable here. The nerve graft is taken from the thigh or the lower leg. Usually, the graft need not be stitched to the severed ends of the nerve.
Hypoglossal facial anastomosis: Hypoglossal nerve is a nerve that supplies the tongue. This nerve is anastomosed (attached) to the severed end of the facial nerve. This helps improve the muscle tone and movement of facial muscles, but the tongue activity is usually affected on that side. The tongue atrophies (becomes smaller) and weakens. However, the disability of the tongue is not that severe, and patients can usually chew and speak comfortably after a few months.
Plastic surgery procedures: These are usually performed in old, long-standing cases of facial nerve damage. They are performed to help improve cosmetic appearance when grafting is not feasible. These procedures include facial slings, muscle transfer, or facelift surgery. The surgeries aim to help in providing movement and symmetry to the face.