Nerve Paralysis PATIENT
|| You are probably wondering why you would see an ear doctor for a problem with your face. This is a natural question. The reason is due to the course of the facial nerve through the ear. The seventh cranial nerve, or facial nerve, has the longest intraosseous course (travel through the bone) of any of the nerves in the head. It travels one and a half inches from the entrance of the ear bone to its exit just below the ear. The facial nerve leaves the brain with the hearing and balance nerves. There are actually two balance nerves, and these four nerves travel through the internal ear canal and enter the ear bone. The facial nerve then travels between the hearing and balance portions of the inner ear and then enters the middle ear to curve around the stapes, or third bone of hearing, and then goes through the mastoid cavity (the ear sinus), behind the external ear, and exits the bone just below the ear, between the jaw bone and the mastoid tip, which can be felt just behind the jaw bone. It then goes across the face to supply the muscles of the face.
During the course of its travels through the ear, the facial nerve has several branches. The first branch of the facial nerve leaves the nerve just as it travels between the balance and hearing portions of the inner ear and goes to supply the tear gland. You may notice dryness or subsequent wetness of the eye depending on the stage of facial nerve involvement you have.
The next branch supplies the stapes muscle and causes tension on this small ear bone with loud sounds. Occasionally, a special test, called a stapedial reflex, is used to measure movement of this muscle using a device called a typmanometer that puts pressure in your ear and emits a brief sound.
The third branch of the facial nerve is the chorda tympani nerve, which goes to the tongue and supplies taste to one side of the front part of the tongue. It is not uncommon to experience a metal taste in the mouth following facial nerve disorders. At last, the facial nerve exits the ear and then supplies the muscles of facial expression. These muscles allow us to blink our eyes, smile, frown, and help us to chew.
The facial nerve is, indeed, a very important nerve, both cosmetically, and functionally. It closes our eye for us and prevents the eye from drying out. In addition, it helps us to chew and swallow our food. It is difficult to keep food inside the mouth when chewing if the facial nerve is weak on one side.
Evaluation of Facial Nerve Problems
There are many tests that are useful in evaluating the facial nerve. One of the most useful is a hearing test to see if there is involvement of the adjacent eighth cranial nerve, or hearing and balance nerve. Occasionally, specialized hearing tests are useful in evaluating the facial nerve.
Imaging studies are also useful at times. This can involve a CT scan which takes thin slices of x-rays through the ear bone. Also, and MRI can which uses magnet images to evaluate the facial nerve is useful. These are often useful to detect if there is any tumor or inflammation involving the facial nerve or adjacent structures.
Measurement of Nerve Action
Sometimes it is useful to stimulate the nerve that moves the face with an electrical probe and measure the responses, which are recorded electronically. This is known as electroneuronography. A less sophisticated but also helpful device is the hand-held nerve stimulator that will elicit a response in the muscles.
Other less useful tests involve measurement of tearing from the eye and taste tests. These are relatively nonspecific and are not used often.
When the facial paralysis has been present for a long time, evaluation of the facial muscles with needle electrodes, called electromyography, is helpful.
Disorders of the Facial Nerves
Bell's palsy (idiopathic facial paralysis) is the most common type of disorder affecting the facial nerve. What it really means is facial paralysis of unknown origin. Recently, there has been a great amount of evidence to suggest that this is, indeed, due to a viral infection that causes swelling of the nerve. Because the nerve is encased in bone, it has no room to swell and expand, and the compression of the bone around the nerve causes a decrease in the blood supply to the nerve and resultant dysfunction. Fortunately, this condition has a good prognosis. 85% of patients with this problem will regain totally normal facial function in the future. Approximately 10% will regain function that is almost normal, such that very few people would notice any problem, but the patient does notice a little difference. About 5% of patients experience noticeable dysfunction following recovery. Almost no one experiences persistent continued complete facial paralysis following this disorder.
The most effective treatment involves the use of cortisone-like medicines that decrease the swelling. It is often useful to use a medicine to fight viral infections if found early in the course of infection.
In some cases in which the facial nerve has degenerated to a large degree as determined by electrical testing, it may be advisable to take the bony covering off the facial nerve through surgery. This usually involves making a cut above the ear and behind the ear and going in alongside the brain, taking the bone off this nerve as well as the bone in the mastoid cavity behind the ear. The risks of this surgery include some unlikely but possible injury to the brain from lifting the brain up during the surgery. Other risks include
hearing loss and dizziness. Most people do not have degeneration to the point that this should be considered.
Herpes Zoster Oticus
This is a condition very much like Bell's palsy, and it is caused by a virus. However, it usually also involves hearing loss and blisters on the outside of the ear. The prognosis is slightly worse for this disorder. However, most people with this disorder also achieve a complete and normal recovery.
Chronic Ear Disease
Very rarely, chronic infections of the ear that result in cyst formation press on the facial nerve and cause facial paralysis. In this situation, it is necessary to remove the cyst surgically, which almost always results in return of facial function.
Occasionally, a brain tumor can cause paralysis of the face, and sometimes removal of a brain tumor can result in facial paralysis. In these cases, it may be necessary to perform some other surgical procedures to help restore facial function.
Injuries to the Facial Nerve
Sometimes due to a blow to the head, the ear bone can be fractured and injure the facial nerve. Sometimes it is necessary to surgically remove pieces of bone that have compressed the nerve to allow return of function. Occasionally, it is necessary to splice another nerve graft into an injured segment to restore function. In these cases, the return of function is never normal, but it is much better than complete paralysis.
This is an uncommon disease in which there are spasmodic contractions of the face on one side. This is thought to be related to an abnormal irritation of the nerve by a blood vessel next to the nerve as it exits the brain. This can often be corrected with surgery that takes this vessel away from that sensitive portion of the nerve and places some Teflon felt between them. This involves an incision behind the ear and is done in conjunction with a neurosurgeon.
The most important thing in the treatment of facial paralysis is to protect the eye. The lack of a blinking response will lead to dryness of the eye. The dryness of the eye can lead to ulceration of the cornea, or covering of the eye, and severe infections and subsequent complications that could lead to loss of vision. As one can see from this discussion, it is necessary to take steps to increase the moisture covering the eye. For this purpose, tear preparations are useful and should be used liberally. Two of the best preparations for this include ReFresh Tears and Celluvisc. These preparations should be used at least every hour and as often as necessary to keep the eye wet.
Often it is helpful to tape the lid down to keep the lid down against the eyeball. This will be demonstrated to you.
A moisture chamber, which is a clear plastic shield that keeps wind off the eye, is also very helpful.
At night, it is advisable to put some ointment in the eye, such as LacriLube, then tape the lids shut so that the eye doesn't come open at night and get scratched.
Should you experience pain or gritty feeling in the eye, it is advisable to see your eye doctor to make sure there is no ulceration of the cornea. In cases of longstanding paralysis in which no return is expected, you may be referred to an ophthalmic plastic surgeon to insert a gold weight in the eyelid to help it close, and you may need some other adjunctive lid-tightening procedures.
Surgery for Facial Paralysis
In some cases, it is necessary to proceed with surgery for facial paralysis. Often this involves going through the ear canal and behind the ear. The hearing and balance portions of the inner ear are at risk with any surgery on the facial nerve. It is unlikely to happen, but occasionally one can lose all of the hearing in the ear and experience some balance disturbances following surgery on the facial nerve.
At times it is necessary to go up over the ear into the skull alongside the brain and lift the brain up off the ear bone and take bone away from the facial nerve. This can result in bruising of the brain and some problems with speech and memory. This is very unlikely to occur, but it is a possibility. Occasionally, there is some leak of fluid from the covering of the brain following this type of surgery that would necessitate another surgery to be repaired. Often during this type of surgery, it is necessary to obtain a small bit of fat from the lower abdomen to seal any leak.
In some cases, the hearing has been lost following an injury to the ear bone in which facial paralysis occurs. In this case, the surgery goes through the inner ear to repair the facial nerve.
In case of longstanding paralysis in which there is no way to connect the two ends of the facial nerve, it is sometimes necessary to connect the nerve that goes to the tongue to the facial nerve. This results in some paralysis of the tongue on one side, but restores some facial function. This allows a great improvement in facial movement and tone but does not restore normal facial nerve function.
In some cases in which the facial paralysis persisted longer than 18-24 months, it is necessary to transpose some of the muscles that are used in chewing to insert into the face to provide some movement of the face. These muscles will provide increased tone of the face and a more normal appearance at rest and will provide some movement that can be trained by clenching the teeth.
There are many conditions that affect the facial nerve. As the facial nerve courses through the ear, there are many things that can involve the ear structures as well. Remember, it is most important to protect the eye in all cases. If you have any questions we will be glad to answer them.
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