What could be more central to our sense of self than our faces? So imagine what it would be like to watch powerlessly while half your face progressively droops like melted wax. That's what happens in Bell's palsy. Bell's palsy is a condition causing weakness or even total paralysis of the muscles on one side of the face, typically developing over 3-72 hours. It can occur at any age and affects the genders about equally. People with diabetes and depressed immune systems are at increased risk of having this condition, as are women in the third trimester of pregnancy. Bell's palsy affects about 11 out of 1000 people sometime during their lives. The problem lies within the facial nerve, also known as the seventh cranial nerve. The nerve is like a telephone-cable and contains thousands of individual nerve-fibers. There are two facial nerves, one for each side of the face, and by far the most common pattern is that one side of the face is affected and not the other. The facial nerve ultimately connects the brainstem (junction between the upper brain and spinal cord located at the base of the skull) to the muscles of the face. Along the way it travels through a narrow canal in the skull bone. After exiting this canal near the bottom of the ear it divides into thousands of tiny branches before reaching the facial muscles. In Bell's palsy the portion of the nerve within the skull's bony canal becomes inflamed for unclear reasons, though an infection with herpes simplex virus (the same virus that causes cold sores) is suspected in most cases. The condition is not contagious. Because the bony canal is rigid and narrow, the swollen nerve-bundle has little room to expand, and compression of the nerve-fibers can further injure them and cause more loss of muscle function. MRI scans of the head can detect the inflammation, but only if gadolinium (the MRI-equivalent of x-ray dye) is infused into a vein prior to scanning. The weakness in the lower facial muscles produces a lop-sided smile. Patients sometimes mis-identify the side of their face that is affected: they focus on the side of the face that is "drawn" rather than on the side that lacks the ability to draw. Weakness in the lower face also interferes with talking, eating and drinking, and beverages can dribble from the corner of the mouth. Weakness of the upper face causes flattening of forehead-wrinkles and inability to raise an eyebrow. But the most significant problem is weakness in the muscles that close the eye, including those involved in blinking. Blinking" ?like other things we take for granted until they're gone" ?is an underappreciated but important activity that cleanses and moistens the front of the eyeball. So people with Bell's palsy experience dryness and irritation of the eye on the side of the weakness. As a result, they try to blink even more frequently, but end up blinking the unaffected eye more than the eye that really needs it. Other symptoms include pain in or behind an ear in about half the cases. Pain usually fades within the first 1-2 weeks of the illness. Because branches of the facial nerve modify the senses of hearing and taste, patients can also notice excessive loudness of sounds, and foods might not taste as they should. Bell's palsy is considered a "diagnosis of exclusion," meaning that other diseases producing similar symptoms should be considered first. For example, especially in childhood, Lyme disease" ?a bacterial infection transmitted by tick bite anywhere on the body" ?can produce a very similar picture, and needs to be treated with an antibiotic drug. In adulthood a different kind of infection, Ramsay Hunt syndrome, needs to be considered, because it should be treated with an antiviral drug. Like Bell's palsy, Ramsay Hunt syndrome damages a facial nerve, but involves the varicella zoster virus, the same virus that produces chicken pox and shingles. Apart from causing facial weakness, this virus typically produces blisters within the ear" ?or sometimes in the mouth or throat" ?that are not seen in cases of Bell's palsy. Strokes can also produce weakness on one side of the face, but almost always produce weakness in other parts of the body as well. Another point of distinction is that strokes seldom interfere significantly with the ability to blink or raise an eyebrow. Fortunately, even without treatment most cases of Bell's palsy do well. About 50% obtain a full recovery within the first six months, with the first hint of improvement occurring after 10 days to two months. Another 35% obtain good, though sometimes incomplete, recovery within the first year. How about treatment? Prescription drugs often receive the most attention because they seem more important or definitive than measures that don't require a doctor's prescription. The two most prescribed medications are anti-inflammatory steroids, like prednisone, and anti-viral drugs, like acyclovir. Based on what is known or suspected about Bell's palsy, their use makes sense. But what seems logical is not always true. Thus far, randomized, controlled trials" ?the gold standard for judging the effectiveness of treatments" ?have shown minimal if any effect of these drugs on the course of symptoms. A little-heralded treatment is probably the most important. And that is to protect the eye. With loss of blinking, the eye needs to be moistened and cleaned in order to prevent irritation and the worst complication" ?secondary infection of the eyeball's surface. During waking hours this can be accomplished with liberal use of unmedicated eye-drops. At bedtime, a soothing, unmedicated ointment" ?like Lacrilube" ?can be squeezed from its tube into the lower eyelid sac. Then the patient can pad and tape the upper and lower eyelids into a shut position overnight. Upon awakening the next morning, he or she can uncover the eye and resume eye-drop treatments. Any loss of vision should be reported promptly to a physician. Can Bell's palsy recur? It does in about 5-9% of cases after an average interval of 10 years. The world's record for recurrences probably belongs to one poor soul described in a Slovakian medical journal as experiencing 11 relapses! (C) 2005 by Gary Cordingley |
