Twitching, weakness or paralysis of the face is a symptom of some disorder involving the facial nerve. It is not a disease in itself. The disorder may be caused by many different disease, including circulatory disturbances, injury, infection or tumor.
Facial nerve disorders are accompanied by a hearing impairment. This impairment may or may not be related to the facial nerve problems. Hearing is measured in decibels (dB). A hearing level of 0 to 25 dB is considered normal hearing for conversational purposes.
Function of the facial nerve
The facial nerve resembles a telephone cable and contains hundreds of individual nerve fibers. Each fiber carries electrical impulses to a specific facial muscle. Acting as a unit this nerve allows us to laugh, cry, smile or frown, hence the name, "the nerve of facial expression". Each of the two facial nerves not only carries nerve impulses to the muscles of one side of the face, but also carries nerve impulses top the tear glands, saliva glands, to the muscle of a small middle ear bone (stapes) and transmits taste fibers from the front of the tongue and pain fibers from the ear canal. As such, a disorder of the facial nerve may result in twitching, weakness or paralysis of the face, dryness of the ear or the mouth, loss of taste, increased sensitivity to loud sound and pain in the ear.
An ear specialist is often called upon to manage facial nerve problems because of the close association of this nerve with the ear structures. After leaving the brain the facial nerve enters the temporal bone (ear bone) through a small bony tube (the internal auditory canal) in very close association with the hearing and balance nerves. Along its inch and a half course through a small bony canal in the temporal bone the facial nerve winds around the three middle ear bones, in back o the eardrum, and then through the mastoid to exit below the ear. Here is divides into many branches to supply the facial muscles. During its course through the temporal bone the facial nerve gives off several branches: to the tear gland, to the stapes muscle, to the tongue and saliva glands and to the ear canal.
Diagnosis of facial nerve disorders
Abnormality of facial nerve function may result from circulatory changes, infections, tumors or injuries. An extensive evaluation is often necessary to determine the cause of the disorder and localize the area of nerve involvement.
Tests of hearing are done to determine if the nerve disorder has involved he delicate hearing mechanism. When the face is totally paralyzed a special hearing test (stapedius reflex) helps to localize the problem area.
X-rays are usually taken to determine if there is any infection, tumor or bone fracture (CT scan or MRI scan)
A test of the eye’s ability to tear may be helpful to determine the location of the facial nerve involvement.
An ENG (Electronystagmography) test of the balance system is advised in some cases to clarify the cause or location of the facial nerve disorder.
There are three electrical tests of the facial nerve function that we may use: nerve excitability test, Electroneurography and electromyography.
Nerve Excitability Test
The facial nerve excitability test helps us to determine the extent of nerve fiber damage in cases of total paralysis. The test may be normal despite the paralysis, indicating a better outlook for return of function. In such cases the excitability test may be repeated every day or so to detect any change which would indicate progressive deterioration.
Electroneurography involves the use of a computer to measure the muscle response to electrical stimulation of the facial nerve. Recording electrodes are placed on the face and the facial nerve is stimulated with small electrical currents. Muscle contractions are recorded by the computer.
Electromyography may be indicated in cases of long-standing paralysis. This test helps us to know if the nerve and muscles are recovering.
The most serious complication that may develop as the result of total facial nerve paralysis is an ulcer of the cornea of the eye. It is important that the eye on the involved side be protected from this complication by keeping the eye moist.
Closing the eye with the finger is an effective way of keeping the eye moist. One should use the back of the finger rather than the tip in doing this to insure that the eye is not injured.
Glasses should be worn whenever you are outside. This will help prevent particles of dust from becoming lodged in the eye.
If the eye is dry, you may be advised to use artificial tears. The drops should be used as often as necessary to keep the eye moist. Ointment may be prescribed for use at bedtime.
At times it is necessary to tape the eyelid closed with tape. It is best for a family member to do this to insure that the eye is firmly closed and will not be injured by the tape.
If facial weakness is anticipated following surgery a silk threat is sometimes placed in the lid to help close it. When lid closure is adequate this is easily removed.
In many cases where longstanding paralysis is anticipated, it may be necessary to insert a gold weight or spring into the eyelid or perform some other longstanding procedure to help the eyelid close.
Bell’s Palsy & Herpes Zoster
The most common condition resulting in facial nerve weakness or paralysis is Bell’s palsy, named after Sir Charles Bell who first described the condition. The underlying cause of Bell’s palsy is not known, but it may well be due to a virus infection of the nerve. We know that the nerve swells in its tight bony canal. This swelling results in pressure on the nerve fibers and their blood vessels. Treatment is directed at decreasing the swelling and restoring the circulation so that the nerve fibers may again function normally.
A condition similar to Bell’s palsy is herpes zoster oticus, "shingles" of the facial nerve. In this condition there is not only facial weakness but often hearing loss, unsteadiness and painful ear blisters. These additional symptoms usually subside spontaneously but some hearing loss may remain.
Treatment of the paralysis in these two conditions may be either medical or surgical. Medical treatment, (with steroids or antiviral medications), may instituted to decrease the swelling and stimulate the circulation.
Mastoid decompression of the facial nerve. Surgical decompression of the facial nerve is indicated in cases of paralysis when the electrical tests show that the nerve function is deteriorating. This operation is performed under general anesthesia and requires hospitalization for two to four days. Through an incision behind the rigid mastoid bone around the swollen nerve is removed, relieving pressure so that the circulation may be restored.
The degree and rapidity of recovery of facial nerve function depends upon the amount of damage present in the nerve at the time of surgery. Recovery may take from 3 to 12 months and may not be complete. Fortunately it is unusual to develop a hearing impairment following surgery but this depends on the extent of surgery needed in the individual case.
Middle fossa facial nerve decompression. At times deeper portions of the facial nerve are affected. In that case surgery may also involve an incision above the ear, with removal of a small portion of the skull. The need for this procedure can usually be determined by tests before surgery.
Mastoid and middle cranial fossa facial nerve decompression. This procedure is a combination of the previously described surgeries.
Risks and complications of facial nerve surgery
All patients notice some hearing impairment in the operated ear immediately following surgery. This is due to swelling and fluid collection in the mastoid and middle ear. This swelling usually subsides within 2 to 4 weeks and the hearing returns to its preoperative level. In an occasional case scar tissue forms and results in a permanent hearing impairment. It is rare to develop a severe impairment.
Dizziness is common immediately following surgery due to swelling of the inner ear structures. Some unsteadiness may persist for a few days postoperatively. On rare occasions dizziness is prolonged.
Related to Middle Fossa Approach
The middle fossa approach to the facial nerve, necessary in some cases, is a more serious operation. Hearing and balance disturbances are more likely following this surgery. Permanent impairment is, nonetheless, uncommon.
A hematoma (collection of blood under the skin incision) develops in a small percentage of cases, prolonging hospitalization and healing. Reoperation to remove the clot may be necessary if this complication occurs.
A CEREBROSPINAL FLUID LEAK (leak of fluids surrounding the brain) develops in an occasional case. Reoperation may be necessary to stop the leak.
Infection is a rare occurrence following facial nerve surgery. Should it develop after a middle fossa approach, it could lead to meningitis, an infection in the fluid surrounding the brain. Fortunately this complication is very are.
Temporary paralysis of half the body has occurred following a middle fossa operation, due to brain swelling. This complication is, however, extremely rare.
Related to Anesthesia
Operations on the facial nerve usually are performed under general anesthesia. There are risks involved with any anesthesia and you may discuss this with the anesthesiologist if desired.
Injuries of the facial nerve
A common cause of facial nerve injury is a skull fracture. This injury may occur immediately or may develop some days later due to nerve swelling.
Injury to the facial nerve may occur in the course of operations on the ear. This complication, fortunately, is very uncommon. It may occur, however, when the nerve is not in its normal anatomical position (congenital abnormality) or when the nerve is so distorted by the mastoid or middle ear disease that it is not identifiable. In rare cases it may be necessary to remove a portion of the nerve in order to eradicate the disease.
Treatment of an injured facial nerve may be medical or surgical, depending upon the extent of nerve damage.
Medical treatment is the same as described for Bell’s palsy.
- Decompression of the facial nerve
- Middle fossa facial nerve decompression.
- Facial nerve graft. A facial nerve graft is necessary at times if facial nerve damage is extensive. A skin sensation nerve is removed from the neck and transplanted into the ear bone to replace the diseased portion of the facial nerve. Total paralysis will be present until the nerve regrows through the graft. This usually takes 6 to 15 months. Some facial weakness is permanent.
The most common tumor to involve the facial nerve is a nonmalignant fibroid tumor of the hearing and balance nerve, the acoustic tumor. Although there is rarely any weakness of the face before surgery, tumor removal sometimes results in weakness or paralysis. This weakness usually subsides in several months without treatment, occasionally it is permanent.
It may be necessary to remove a portion of the facial nerve in order to remove the acoustic tumor. Rarely, it may be possible to sew the nerve ends together at the time of surgery or to insert a nerve graft. At times a nerve anastomosis procedure is necessary later, connecting a tongue nerve to the facial nerve (hypoglossal-facial anastomosis-page 16). In either case the face is totally paralyzed until the nerve regrows (6 to 15 months).
Facial Nerve Neuroma
A nonmalignant fibroid growth may grow in the facial nerve itself. This tumor may or may not produce a gradually progressive facial nerve paralysis. Removal of this facial nerve neuroma requires removing that portion of the facial nerve invaded by tumor. Usually it is possible to graft it at the time with a skin sensation nerve from the neck. Total paralysis will be present until the nerve regrows through the graft, usually a period of 6 to 15 months. There will be some permanent facial weakness.
When the portion of the facial nerve nearest the brain is destroyed by the tumor, a facial reanimation procedure may be necessary (see below).
Removal of a facial nerve neuroma may necessitate removal of the inner ear structure. If this were necessary, it would result in a total loss of hearing in the operated ear and temporary severe dizziness. Persistent unsteadiness is uncommon.
There are a number of surgical procedures that are helpful for patients with facial paralysis. In some cases, repairing or decompression an injured nerve is an important consideration. There are a variety of other procedures that may be helpful to prevent drying or injury of the eye and assist in improving symmetry or even movement of the face although none of these procedures can create a perfectly normal appearance of the face.
Implantation of gold or a spring into the upper eyelid can be helpful in counter balancing the lifting eyelid muscle. This helps to prevent dryness and irritation of the eye and helps to improve the appearance. Shortening of the lower lid or corners of the eyelid are sometimes performed at the same operation. Complications of these procedures are rare and include bleeding, infection, droopy eyelid, extrusion of the implant and visual loss.
Hypoglossal-Facial Nerve Anastomosis
Connection a portion or all of the tongue nerve to the facial nerve may provide good tone to the face. Facial movements can also be obtained by attempting to move the tongue to the involved side when a smile is desired. Some degree of tongue weakness is expected which may affect speech or swallowing.
Temporalis Muscle Transposition
Transferring one of the jaw muscles to the corner of the mouth can provide improvement of facial symmetry. Smiling is relearned by attempting to bite at the same time. Unlike hypoglossal-facial nerve anastomosis, no tongue weakness is expected and chewing problems are rare. The surgeon always attempts to overcorrect the pull at the corner of the mouth. This over-correction and the significant face swelling usually resolve in 4-6 weeks. Rarely, a very thick muscle may result in a bulge.
While facial reanimation surgery cannot provide a return to normal facial function, the improvement in eye protection and appearance is usually gratifying. Not infrequently, a secondary procedures or revisions may be required to obtain the best results or modify results because of the passage of time.
There are a variety of other operations that are sometimes performed by themselves or in combination with the above procedures. Such procedures may include a face lift or removal of excess skin at the brow or cheek. For patients who have some faulty return of facial function, selective cutting of facial nerve branches or facial muscles may be of benefit and are sometimes combined with other procedures to correct some of the anticipated weakness.
Other Facial Nerve Disorders
Surgery to correct this problem may involve: 1) intentional weakening of the nerve through an incision on the face which may also require a gold weight eyelid implant, or 2) relieving pressure on the nerve adjacent to the brain. This operation includes risks of facial paralysis, hearing loss, dizziness, spinal fluid leak and stroke. As always, you should discuss your proposed surgery in detail with your doctor.
Acute or chronic middle ear infections occasionally cause a weakness of the face due to swelling or direct pressure on the nerve. In acute infections the weakness usually subsides as the infection is controlled and the swelling around the nerve subsides.
Facial nerve weakness occurring in chronically infected ears is usually due to pressure from a cholesteatoma (skin-lined cyst). Mastoid surgery is performed to eradicate the infection and relieve nerve pressure. Some permanent facial weakness may remain.
Postoperative Facial Nerve Weakness
Delayed weakness or paralysis of the face following reconstructive middle ear surgery (myringoplasty, tympanoplasty, stapedectomy) is uncommon, but occurs at times due to swelling of the nerve during the healing period.
Fortunately this type of facial nerve weakness usually subsides spontaneously in several weeks and rarely requires further surgery.
Hemifacial spasm is an uncommon disease of unknown cause which results in spasmodic contractions of one side of the face. Extensive investigation is necessary at times to establish the diagnosis correctly. In some cases, a hemifacial spasm is caused by irritation of the facial nerve near the brain. Examination of the nerve and correction of the irritation, if present, is possible by the retrolabyrinthine or retrosigmoid surgical approach. Facial nerve decompression (see Bell’s palsy) may be beneficial.
In this operation the area between the brain and the inner ear is exposed by removing the mastoid bone behind the inner ear. The complications related to the surgery are the same as those for the middle fossa approach (pages 11 and 12).
Tumors and circulatory disturbances of the nervous system may cause facial nerve paralysis. The most common example of this is a stroke.
As opposed to other conditions listed in this booklet, in brain diseases there are usually many other symptoms which indicate the cause of the problem. Treatment is managed by the internist, neurologist or neurosurgeon.
During the period of recovery of facial function, exercises may be recommended. We do not usually recommend electrical stimulation of the facial muscles.
As recovery of facial nerve function begins, biofeedback exercises may be recommended by your otologist.