The facial nerve, also known as cranial nerve #7, is one of the twelve paired cranial nerves. There is a facial nerve for the right and left side of the face. The facial nerve travels a long distance from the centre of the brain (brainstem) out to the muscles of the face. During much of this course, the facial nerve is encased in a bony canal, which may make it prone to injury when nerve swelling occurs.
As suggested by its name, the facial nerve is responsible for much of the movement of the face; it closes the eyelids, lift the eyebrows, and helps you to smile. The facial nerve also dampens noise from the ear drum, and has a partial role in helping you taste things. (Some or all of these functions may be compromised when the facial nerve is injured.) The facial cranial nerve can be “underactive” as in a Bells palsy, or “overactive” as in hemifacial spasm.
BELLS PALSY: is a weakness of the seventh cranial nerve named after Dr. Charles Bell. Patients with Bells palsy have a “droopy” face on the affected side. Bells palsy usually occurs suddenly but should not be confused with a “brain” stroke. Many people get Bells palsy (apparently George Clooney had one in high school, Pierce Brosnan 007, 2 members of Dr. Ing’s family, and perhaps Mona Lisa!). Bells palsy occurs more often in patients that are diabetic, pregnant women, and in patients with a family history of Bells palsy.
Causes for facial nerve weakness (palsy) other than Bells palsy include: facial trauma, brain tumours (especially after acoustic schwannoma surgery), partoid gland tumours, herpes zoster, lyme disease, sarcoidosis and leprosy. Unlike Bells palsy that occurs suddenly, facial nerve palsy from tumours is usually slowly progressive.
Most patients with Bells palsy will recover by themselves over weeks to months. During the recovery period patients must lubricate the eye on the affected side until adequate blinking returns. Patients should see an ophthalmologist regularly to ensure that the cornea is not being damaged with the Bells palsy. If the cornea dries out from exposure, or becomes infected, permanent corneal scarring may result.
Other causes of facial nerve palsy do not have as good a prognosis as Bells palsy. If the facial nerve has to be cut during brain surgery, the function of the facial nerve will not recover. If a facial nerve palsy does not appear to be improving, neuroimaging (CT or MRI) may be performed.
TREATMENT: Although Bells palsy usually resolves by itself, up to 15% of patients may not recover well. For this reason many doctors will prescribe steroid pills. The November 2015 Cochrane review suggested there is low to moderate quality evidence for the use of antivirals in addition to corticosteroids.
If the facial nerve has not recovered after a few months, surgery may be considered. If the lower eyelid is drooped outwards (ectropion) it can be surgically tightened. If the cheek is drooped, it can be lifted to help close the eye. A gold weight can be sewn in to the upper lid to help it close. A permanent lateral tarsorraphy (sewing the lids together) can be performed if needed. The tear drainage holes (puncta) can be cauterized to conserve moisture.
If the facial nerve was cut during brain surgery, a neurosurgeon may connect the 12th cranial nerve with the 7th cranial nerve (hypoglossal facial anastamosis) to try and improve function.
Patients with continuous, uncontrolled blinking may have:
Blepharospasm and hemifacial spasm are usually treated with BOTULINUM injections.** Botulinum or Botox can be thought of as a long acting muscle relaxant that takes 304 days to work, but lasts 3-4 months. Botox injections are usually repeated every 3-4 months. Botox is expensive but is covered by some insurance plans. If you are bringing the botox to Dr. Ing’s clinic, pack it in a cooler with ice. Ensure that the pharmacist has enclosed the saline, and syringes for Dr. Ing.
If blepharospasm does not respond to botox injections, eyelid surgery to excise the overactive muscles may be required. Restorative lid surgery may also be required since the chronic blinking often stretches the eyelid tissues. Artificial tears, rose coloured lens tint (FL-41), lorazepam, chewing gum, and singing may also help patients with blepharospasm function better.
If hemifacial spasm does not respond to botox injections, a very involved brain operation by a neurosurgeon (posterior fossa microvascular decompression) can be considered.