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A Discussion of Facial Nerve Problems
Spasm, 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 diseases,
including circulatory disturbances, infection, or tumor.
FUNCTION OF THE FACIAL NERVE
The facial nerve resembles a telephone cable and contains
hundreds of individual nerve fibers. Each fiber carries electrical
impulses from the brain 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."
The facial nerve not only carries nerve impulses to the muscles
of one side of the face; but also carries nerve impulses to
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 spasm, weakness
or paralysis of the face, dryness of the eye or mouth, loss
of taste and, occasionally, 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 travels near the three middle ear bones, in back
of the ear drum, and then through the mastoid to exit below
the ear. Here it 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. The facial nerve does not supply the muscle
used in chewing.
CAUSES OF FACIAL NERVE DISORDERS
Bell's palsy
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 felt to be due to a viral infection of the
nerve or inflammation 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.
Herpes Zoster Oticus
A condition similar to Bell's palsy is herpes zoster oticus
or "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 or unsteadiness
may remain.
Injuries of the Facial Nerve
The most common cause of facial nerve injury is due to 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 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.
In more complicated ear problems, such as tumors of the hearing
and balance nerve, the facial nerve may be injured and at
times, the nerve must be severed to allow complete removal
of a tumor.
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.
Tumors
Acoustic Tumors: The most common tumor to
involve the facial nerve is a nonmalignant tumor to the hearing
and balance nerve called an acoustic neuroma (vestibular schwannoma).
Although there is rarely any weakness of the face before surgery,
tumor removal sometimes results in weakness or paralysis due
to the close proximity of the facial nerve. This weakness
usually subsides in several months without treatment.
It may be necessary to remove a portion of the facial nerve
in order to remove the acoustic tumor. In that case, the face
is totally paralyzed until the nerve is repaired and has had
a chance to regrow. 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, connecting
a tongue or shoulder nerve to the facial nerve.
Facial Nerve Neuroma: A nonmalignant growth
may grow in the facial nerve itself, producing a gradually
progressive facial nerve paralysis.
It may be necessary to severe or remove a portion of the facial
nerve in order to remove a facial nerve neuroma. An attempt
is made to sew the nerve ends together at the time of surgery
or to insert a nerve graft. The nerve used in grafting is
taken from a skin sensation nerve in the neck. Total paralysis
will be present until the nerve regrows through the graft,
usually a period of 6 to 24 months. At times, a nerve procedure
is necessary later, connecting a tongue nerve to the facial
nerve (hypoglassal-facial anastomosis). In all of these situations
there will be some permanent facial weakness.
Removal of a facial nerve neuroma may necessitate removal
of the inner ear structures. If this is necessary, it results
in a total loss of hearing in the operated ear and temporary
severe dizziness. Persistent unsteadiness is uncommon.
Infection
Acute or chronic middle ear or mastoid 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 cyst).
Mastoid surgery is performed to eradicate the infection and
relieve nerve pressure. Some permanent facial weakness may
remain.
Brain Disease
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 neurotologist in conjunction with an internist, neurologist,
or neurosurgeon.
Hemifacial Spasm
Hemifacial spasm is an uncommon disease which results in spasmotic
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 an irritation
of the facial nerve by a blood vessel near the brain. Examination
of the nerve and correction of the irritation, if present,
is possible by a surgical approach.
DIAGNOSIS OF FACIAL NERVE DISORDERS
An extensive evaluation is often necessary to determine the
cause of the disorder and localize the area of nerve involvement.
Hearing Evaluation
Tests of the hearing are done to determine if the nerve disorder
has involved the delicate hearing mechanism. Facial nerve
disorders are accompanied at times by a hearing impairment.
When the face is totally paralyzed, a special hearing evaluation
(stapedius reflex) helps to localize the problem area.
ABR (auditory Brainstem response) testing is a sophisticated
computerized hearing evaluation which evaluates the neural pathways
of hearing through the Brainstem. These are pathways closely
related to those of facial function. Abnormalities here help
to further define the nature of the facial nerve disorder.
Hearing is measured in decibels (dB). A hearing level of 0
to 25 dB is considered serviceable hearing for conversational
purposes.
Balance Tests
Special testing of the balance portion of the inner ear may
be necessary in some cases to clarify the cause or location
of the facial nerve disorder. Conventional balance testing
involves measuring the eye movements relative to stimulation
of the ear in a test called electronystagmography (ENG).
Imaging (X-rays)
MRI (magnetic resonance imaging) and CT (computer tomography)
are both head scans highly capable of determining if the facial
nerve disorder is due to tumor, infection, bone fracture or
vascular conditions such as stroke. In some cases, it may
be necessary to obtain special x-ray studies of the blood
vessels (angiography) in the area of the brain or ear.
Nerve Stimulation Tests
Facial nerve stimulation or nerve excitability tests help
to determine the magnitude of nerve fiber damage in cases
of facial paralysis. It is an estimation of the health of
the nerve and may be useful in helping to predict ultimate
functional recovery of the paralysis. Despite the presence
of obvious facial paralysis, these tests are capable of indicting
the degree of damage which is occurring. These tests may be
repeated regularly, perhaps daily; so as to detect any change,
for better or worse, in the overall process of paralysis.
Nerve excitability testing includes maximum stimulation tests
(MST) and the more sophisticated electroneurongraphy (ENOG)
or evoked electromyography (EEMG).
In cases of long-standing facial paralysis, an EMG (electromygraph)
may be requested. This test helps determine the status of
nerve and facial muscles in the recovery process.
MANAGEMENT
Treatment of facial nerve weakness or paralysis may be supportive,
medical, eye care, surgical, or a combination of all four.
Medical Treatment
Medical treatment is instituted to decrease the swelling.
It often involves the use of steroids. This treatment may
be continued until the nerve shows sign of recovery.
Eye Care
The most serious complications that may develop as the result
of total facial nerve paralysis are an ulcer of the cornea
of the eye. It is most important that the eye on the involved
side be protected from this complication.
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. Contact lenses should not be worn in this situation.
The advice of your eye doctor should be sought.
If the eye is dry, you may be advised to use eye drops. The
drops should be used as often as necessary to keep the eye
moist. Ointment may be prescribed for use at bedtime.
The best protection for night/sleep hours is to place a clear
eye guard over the eye. This can be secured in place with
tape. Eye care must be compulsive! Any eye problems or irritation
which does not quickly pass should warrant consultation with
your eye doctor as soon as possible.
If facial weakness is anticipated following surgery, a silk
thread is sometimes placed in the lid to help close it. When
lid closure is adequate this easily removed.
In some cases of long-standing paralysis, it may be necessary
to insert a weight into the eyelid to close the eye or perform
some other procedure to help the eyelid close (i.e. tarsorrhaphy).
Surgical Treatment
Surgical treatment for facial paralysis is very controversial.
Surgery to decompress the swelling facial nerve is indicated
in very special and well defined circumstances. Surgical facial
nerve treatment is not applicable to everyone.
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 18 months
and may not ever 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.
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
or a fracture is present. This operation is performed under
general anesthesia and requires hospitalization for 1 to 2
days. Through an incision behind the ear the mastoid bone
around the nerve is removed, allowing repair of a nerve or
relieving pressure so that the circulation may be restored.
Middle fossa facial nerve decompression. This procedure involves
making an incision above the ear, and making a small opening
in the skull. This procedure allows pressure to be relieved
from the nerve or repair of a nerve, if injured.
Retrosigmoid facial nerve decompression. In certain conditions
such a hemifacial spasm or facial nerve tumors, the facial
nerve may need to be investigated where it enters the brain.
This is performed through an incision behind the ear and removal
of either the mastoid bone or a portion of the skull just
behind the mastoid. This exposes the area between the brain
and the inner ear to allow appropriate treatment.
Translabyrinthine facial nerve decompression and repair. In
certain situations, the hearing and balance function of the
inner ear is destroyed by the same process causing the facial
paralysis. Usually this is trauma or a tumor. In this instance,
the inner ear structures for balance and hearing may be removed
to give greater access to repair the facial nerve.
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.
Hypoglossal-facial nerve anastomosis. When it is not possible
for a facial nerve connection by other means, the nerve to
the muscles of one side of the tongue is connected to the
facial nerve. Usually, this occurs when the facial nerve is
severed during tumor surgery or trauma and may be performed
immediately or up to several years after the injury. Surgery
is performed under general anesthesia. The previous incision
behind the ear is opened and extended into the neck. The nerve
to the tongue (hypoglossal nerve) is cut and then connected
to the facial nerve. In 6 to 12 months, when the tongue nerve
grows into the facial nerve, a variable degree of facial motion
returns. Facial appearance may be nearly normal at rest. There
will be some persistent weakness of the face. On moving the
face, all of the muscles tend to contract at once, and some
face motion may occur when speaking. Weakness and wasting
of one half of the tongue develops following cutting of the
hypoglossal nerve. This results in some difficulty in speaking,
chewing and swallowing. Although the tongue weakness is permanent,
it is rare for a severe disability to persist.
RISKS AND COMPLICATIONS OF FACIAL NERVE SURGERY
The surgeon carefully weighs the risks and complications of
each procedure for the individual patient. Surgery is not
recommended unless the benefits derived from surgery to optimize
the return of facial nerve function far outweigh the risks
and complications of surgery. Patients are required to carefully
study the risks and complications of surgery so they may make
a thoughtful, informed consent if surgery is decided upon
by the patient and the surgeon. Patient questions are encouraged
so the patient has a clear understanding of the facial nerve
problem and the options available for management.
Hearing Loss
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 2-4 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, unless a translabyrinthine
approach was utilized.
Dizziness
Dizziness is common immediately following surgery due to swelling
in the mastoid and unsteadiness may persist for a few days
postoperatively. On rare occasions dizziness is prolonged.
Other Complications
A hematoma (collection of blood under the skin incision) develops
in a small percentage of cases, prolonging hospitalization
and healing. Re-operation may be necessary to remove the blood.
A cerebral spinal fluid leak (leak of fluid surrounding the
brain) develops in an occasional case. Re-operation may be
necessary to stop the leak.
Infection is a rare occurrence following facial nerve surgery.
Should it develop, however, after an intracranial procedure,
it could lead to meningitis (infection in the fluid surrounding
the brain). Fortunately, this complication is very rare.
Brain injury or stroke, which may lead to paralysis or other
neurologic disability, has occurred following intracranial
operations for facial nerve repair. This complication is,
however, extremely rare.
Related to Intracranial Surgery
The middle fossa, retrolabyrinthine/retrosigmoid, and translabyrinthine
approaches to the facial nerve, absolutely necessary in some
cases, are more serious operations. Hearing and balance disturbances
are more likely following this surgery.
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.
GENERAL COMMENTS
During the period of recovery of facial function, exercises
may be recommended. Exercising the muscles by wrinkling the
forehead, closing the eyes tightly, and smiling forcefully
may be beneficial.
Electrical stimulation of the facial muscles is usually not
recommended. Electromyographic biofeedback may be used during
rehabilitation of the facial nerve injury to educate and instruct
patients in facial muscle contraction.
Should any questions arise regarding your problem, feel
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