Facial Nerve Paralysis
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What is a facial nerve?
Facial nerve is the 7th of 12 cranial nerves. It emerges from the brain stem and goes through a complex route to reach the muscles of facial expression including keeping the eyebrows high and
closure of the eyelids.
What are the causes of facial nerve paralysis?
Facial nerve paralysis may be congenital or acquired. Acquired causes include infection (Bell’s Palsy), vascular lesions, tumours (acoustic neuroma, parotid gland or temporal bone tumour) or trauma (birth, temporal bone fracture).
What are the symptoms?
The paralysis usually affects one half of the face. Patients with facial nerve paralysis develop flattening of the affected half of the face with loss of forehead wrinkles, inability to whistle and dragged appearance of the opposite corner of the mouth. Eye findings include eyebrow drooping, elevation or retraction of the upper eyelid, sagging and ectropion (outward turning of the lid margin) of the lower eyelid, watering lagophthalmos (inability to close the eye) and exposure keratopathy (drying of the cornea).
How is this condition managed?
Many patients can be managed medically with topical lubrication drops and ointment using artificial tear preparations and taping the eyelids closed at bedtime.
When is a surgical procedure required?
Surgical procedures may be advised for facial nerve paralysis based on the individual clinical presentation. The primary aim of treatment is to protect the cornea (black window of the eye) since it may undergo drying due to poor lid closure and thus protect the eye sight. The other reasons for a surgical procedure include cosmesis and reducing the watering.
Various surgical procedures:
Lateral Tarsorraphy – Surgical closure of the outer portion of the eyelids will frequently suffice to narrow the palpebral fissure and decrease evaporation. Due to its poor cosmetic result, it is often reserved for extreme situations only. This procedure can be reversed and the lids can be opened up if nerve function recovers.
Lateral Tarsal Strip Procedure – This procedure involves tightening of the lower eyelid and is performed when the eyelid is lax and sagging. The eyelid is shortened and reattached to the bony outer orbital rim.
Medial Canthoplasty – This procedure may be required to pull up the sagging lower lid, especially in the inner corner.
Gold Weights – More animated closure of the eyelids can be obtained with placement of a gold weight in the upper lid. This may be done externally or fixed inside the upper lid by a surgical procedure. The weight acts by gravity to help close the eyelids in the relaxed state.
Brow ptosis correction – There are several different procedures to correct the position of the drooping eyebrow. Some are done directly over the eyebrow while others may be carried out via the forehead or the scalp. This is often necessary for cosmetic reasons while in some situations it is necessary to improve the field of vision.
Neurotrophic Keratitis can accompany facial paralysis when surgery is performed for an acoustic neuroma because of associated involvement of the first division of the 5th cranial nerve (nerve sensation to the cornea). Patients have diminished sensation of the cornea (front surface of the eye) and cannot feel dryness or foreign bodies which can rub on the corneal surface. These eyes have a significant incidence of corneal ulceration.
a. Eyelid closure with suture tarsorrhaphy will be necessary for the ulcer to heal.
b. Subtotal medial and later tarsorrhaphy or canthoplasty with central opening may be necessary to protect the cornea.
Crocodile Tears – This is a rare sequelae of facial nerve paralysis. This happens due to abnormal connections between the tear production pathway and chewing muscles, during the recovery phase of the facial nerve paralysis. As a result, one may experience copious and embarrassing tearing while eating. This can be successfully managed using repeated injections of the botulinum toxin.
Follow up in clinic is required as long as the cornea is at risk from exposure.