Hopefully you will never find yourself in a plight where, while watching football in a crowded bar, your face suddenly droops. Only one side of your face is immobile--you’re unable to smile, wink, or whistle.
“What the ____ (insert your favorite 4-letter expletive)?!” scream you at the top of your lungs, though your speech is slurred from lip weakness or that fourth mug of beer you just inhaled.
Astonished people turn to the source of the outburst, not so much from the cursing (since many are using an amazing array of nasty 4-letter expressions) but from the funny—though entertaining--sound of slurred cuss-words. Then someone in the crowd proclaims with authority, “Hey, you’ve got Bell’s Palsy!” Everyone pats this gal on the back and buys her a beer, laughs and resume game-watching. Only you’re there with droopy face and empty glass.
What gives?
Bell’s Palsy is a form of facial paralysis or paresis, resulting in weakness of one side of the face. To clarify the medical lingo, paralysis is a complete inability to move a muscle or muscles, where in paresis there still is movement albeit weaker than normal. In the case of facial paralysis or paresis, it typically is a result of some insult or injury to the nerve that innervates the muscles of the face, ingeniously called the facial nerve. The nerve exists from the ear and then splits into multiple branches to innervate the muscles in the face, muscles required to move the lips and eyes, smile, wrinkle the nose, raise the eyebrows in surprise or lower them in a frown (i.e., from boredom reading this post), etc.
Anatomy
To improve understanding, we always should touch on a bit of anatomy. If you’re already drinking, think of yourself as an inebriated medical student.
The facial nerve arises from the brainstem. I won’t go into all the complex neuropathways within the brain since this would be an entire course in itself, and my fingers are beginning to cramp from the drawing and typing. As such, we’ll keep it simple.
The facial nerve leaves the brainstem and travels towards the inner ear along with nerves to the cochlea and vestibular system. These nerves then enter the internal auditory canal (IAC for short). The facial nerve separates from the others and travels above the cochlea and bends forward to form the geniculate ganglion. From the ganglion a small branch called the greater petrosal nerve arises and travels forward to the lacrimal gland (creates tears) by the eye and to the back of some of the sinuses. The facial nerve then bends posteriorly (backwards) under one of the semicircular canals, then bends inferiorly (downward) in the mastoid bone. A small branch goes to the stapedial muscle, which prevents movement of the stapes bone when the ear is exposed to harmful loud noise—a method to protect the cochlear. As it descends further in the mastoid, it gives off the chorda tympani, which travels to the tongue and provides the sensation of taste. The nerve then leaves the mastoid and into soft tissue, namely the parotid gland, where it then divides into numerous branches to supple the many muscles of the face.
Symptoms
When the facial nerve is impaired, the facial muscles are weak or sometimes completely immobile. In Bell’s Palsy, generally the entire face is involved, with varying degrees of weakness. As noted from the title picture, there are at least 5 main branches of the facial nerve after it exits the ear. Problems with raising the forehead, closing the eye, smiling, raising the nasolabial fold (the skin crease that extends from the side of the nose to the outer corner of the lip), pursing the lips, or tightening the platysma (thins sheet of neck muscle) can occur. Some folks have a small branch that travels to the muscles to the outer ear, which allows for wriggling of the ears (an uncommon, nonvital but entertaining feature).
Problems can arise from the small nerve branching from inside the ear. Diminished tearing occurs due to the greater petrosal nerve impairment. Impaired function of the branch to the stapedial muscle can make one sensitive to sound. If the chorda tympani is impaired, decreased or distorted taste is noted. Some folks describe a metallic taste on the same side of the tongue.
Causes and Treatment
There are a number of causes for facial nerve weakness, such as tumors, trauma, infections, a stroke. We’ll actually cover these in another post.
Bell’s Palsy is actually a diagnosis of exclusion, and is defined by us smart medical folks as idiopathic, meaning “we don’t know.” In other words, after other causes of facial paresis/paralysis have been ruled out, we then call it Bell’s Palsy.
Given the sudden onset, inflammation is the presumed cause of Bell’s Palsy, more specifically it is believed to be caused by the Herpes zoster virus. It occurs within a day or two, and often associated with no other illness. It is also believed the portion of the nerve inside the IAC is involved. Thus, the treatment often includes a course of steroids, such as prednisone. Steroids are strong anti-inflammatory drugs. Usually a high dose is started, such as 60mg of prednisone daily (or 10mg/kg of body weight for lighter folks) for 5-7 days, and then a tapering down on the dose over the next week or more. Side effects include stomach upset, elevated blood sugars and mood changes (which can vary from euphoria to irritability to emotional lability). Weigh gain also can occur. Needless to say, steroids must be tailored to the specific individual, taking into account other medical problems.
Antiviral agents are often given along with a steroid such as acyclovir or ganciclovir.
Other treatments include:
-keeping the eye moist.
This is ultra-important. Often
eyelid closure is weakened, which can lead to corneal dryness and corneal
abrasions. Artificial tears should be
used ever 1-2 hours while awake. At
bedtime, a lubricant called Lacrilube is placed over the eye and the eyelid is
then pulled down. Avoid taping the eye
closed: the tape can loosen and the eyelid might raise, exposing the cornea to
the tape, resulting in an abrasion or trauma
-facial nerve stimulator.
Done with speech therapist or physical therapist. Keeps muscles moving, can prevent synkinesis,
may improve nerve function.
-Surgery: We won’t go into detail on the variety of
surgery. Since swelling of the nerve
seems to occur in the IAC, it was thought that decompression of the nerve as it
enters the inner ear from the ear could help, but needs to be done shortly
after onset of the weakness. This is
somewhat controversial, and requires a major neurosurgical procedure to
accomplish this, and the fact that the majority of patients recover without
surgery.
-Facial reanimation procedures can be done for those who don’t recover completely, usually considered after 3-6 months: A gold weight placed into the upper lid helps eye closure, facial sling using tendon grafts to raise the nasolabial fold, brow lifts to raise the eyebrow and a connecting other nerves in the neck to the facial nerve are a few of the assorted surgical options.
Natural History
The good news with Bell’s Palsy is the majority will recover completely, approximately 85% within a month will have normal or near-normal return of function. It is estimated that about 1/3 recover without any medical treatment. The residual 15% have varying degrees of paresis, some with complete paralysis. It is in these patients that surgery to improve facial function is then contemplated.
Head for to your doctor’s right away if you find your face a-drooping; most often patients need to head for urgent care or the ER to make sure there are no other causes of the weakness. If Bell’s Palsy is diagnosed, the sooner treatment is started, the better the outcome. You can then one day resume your boisterous shouting with clearly articulated swear-words, unimpeded by nuisance slurring.
©Randall S. Fong, M.D.
For more topics on medicine, health and the weirdness
of life in general, check out the rest of the blog site at randallfong.blogspot.com
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