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TINNITUS (HEAD NOISE)
Tinnitus is an abnormal perception of a sound which is reported
by patients that is unrelated to an external source of stimulation.
Tinnitus is a very common disorder. It may be intermittent,
constant or fluctuant, mild or severe, and may vary from a
low roaring sensation to a high pitched type of sound. It
may or may not be associated with a hearing loss. It is also
classified further into subjective tinnitus (a noise perceived
by the patient alone) or objective (a noise perceived by the
patient as well as by another listener). Subjective tinnitus
is common; however, objective tinnitus is relatively uncommon.
The location of tinnitus may be in the ear(s) and/or in the
head.
Tinnitus is a symptom much like a headache, pain, temperature,
hearing loss or vertigo. With tinnitus, the reported distress
is usually subjective and difficult to record and appreciate
by others.
The quality of the tinnitus refers to the description by the
patient of the tinnitus: It may be a ringing, buzzing, cricket,
ocean, etc., type of sound. The quality may be multiple sounds
or a singular sound.
Tinnitus may be produced in one or more locations, called
its site of lesion. The cause of tinnitus may be singular
or multiple. A peripheral (i.e., auditory nerve or cochlea)
site of lesion includes dysfunction established within the
auditory system that extends up to but not involving the brainstem.
A central site of lesion refers to involvement of the central
auditory pathways, beginning at the brainstem and involving
other portions of the central nervous system.
Tinnitus is, therefore, a symptom of neurotologic disease.
It may occur with a hearing loss, vertigo or pressure symptoms
in the ear or it may occur alone.
Tinnitus must always be thought of as a symptom and not a
disease, just as pain in the arm or leg is a symptom and not
a disease. Because the function of the auditory (hearing)
nerve is to carry sound, when it is irritated from any cause
it produces head noise. This phenomenon is similar to the
sensation nerves elsewhere. If one pinches the skin, it hurts
because the nerves stimulated carry pain sensation.
A complete cochleovestibular evaluation is necessary in all
patients with severe disabling tinnitus. The test battery
is used to attempt to establish the site of lesion and to
rule out any significant pathology which may require further
treatment. There are many causes just related to the ear which
would result in tinnitus. Such things as simple ear wax in
the ear canal to other middle ear abnormalities may result
in tinnitus. Otosclerosis (fixation of the stapes bone in
the middle ear) can cause tinnitus as well as fluid in the
middle ear. There are many other ear abnormalities which may
cause tinnitus. A more common example would be Meniere's disease.
Sudden trauma to the inner ear such as exposure to excessively
loud sounds may result in tinnitus. Tumors on the hearing
nerve or other problems in the brainstem or central nervous
system may also cause tinnitus. In addition, other vascular
abnormalities in the skull or base of the skull may result
in tinnitus.
MEASUREMENT OF TINNITUS
Since tinnitus often has high pitch, frequency judgments in
this region normally are poor. Frequency discrimination up
to approximately 16,000 Hz (which is the upper limit of hearing)
is far less exacting than the middle frequency region. In
addition, patients suffering from high pitched tinnitus often
have a high frequency hearing loss which may impair their
frequency discrimination. Therefore, test-retest reliability
in matching the frequencies of audiometer tones to the pitch
of tinnitus may be poor. An attempt is occasionally made,
however, to do pitch-matching and loudness-matching. In addition,
an attempt may be made to determine the maskability of the
tinnitus (which is unrelated to its loudness) and a determination
of residual inhibition can be made (i.e. when tinnitus is
temporarily reduced after a masking sound has been turned
off; the reduction is termed "residual inhibition.")
FUNCTION OF THE NORMAL EAR
The ear is divided into three parts: An external ear, a middle
ear and an inner ear. Each part performs an important function
in the process of hearing.
The external ear consists of the auricle (pinna) and ear canal.
These structures gather the sound and direct it down the ear
canal towards the ear drum membrane.
The middle ear chamber lies between the external and the inner
ear and consists of an eardrum membrane and the three small
ear bones (ossicles): malleus (hammer), incus (anvil) and
stapes (stirrup). These structures transmit the sound vibration
to the inner ear. In so doing, they act as a transformer,
converting the sound vibration to the inner ear.
The inner ear chamber contains the microscopic hearing and
balance nerve endings (hair cells) bathed in fluid. Fluid
waves initiated by movement of the stapes bone stimulate the
delicate hearing nerve endings which in turn transmit an electric
impulse to the brain where it is interpreted as sound.
TYPE OF HEARING IMPAIRMENT
The external ear and the middle ear conduct the transformed
sound; and inner ear receives it. When there is some problem
in the external or middle ear, a conductive hearing impairment
occurs. When the trouble lies in the inner ear, a sensorineural
or hair cell loss is the result. Difficulty in both the middle
and inner ear results in a mixed (i.e., conductive and a sensorineural)
impairment.
FINDINGS IN YOUR CASE
o You have a conductive (middle ear) impairment.
o You have a sensorineural (inner ear or hair cell) impairment.
o You have a mixed (conductive and sensorineural) impairment.
Hearing is measured in decibels (dB). The hearing level of
0 to 25 dB is considered normal hearing for conversational
purposes.
Your hearing level is:
Right ear _____________________ decibels
Left ear _____________________ decibels
(Conversion to degree of handicap)
25dB.........................0% 55dB(Moderate)............45%
30dB(Mild)....................8% 65dB(Severe)................60%
35dB(Mild)..................15% 75dB(Severe)...............75%
45dB(Moderate).........30% 85dB(Severe)...............90%
Your word recognition in quiet is:
Right ear _____________________%
Left ear _____________________ %
SITES AND TYPES OF LESIONS PRODUCING TINNITUS
EXTERNAL AUDITORY CANAL LESIONS
Obstruction of the external auditory canal by wax or other
foreign bodies may cause a sensation of fullness in the ear
with decreased hearing and when this is present, the patient
may experience tinnitus. Usually, this is resolved once the
obstruction in the ear canal is removed.
VASCULAR LESIONS
The heart's pumping and blood circulation normally are only
occasionally heard by the patient in the silence of a sound-proofed
room. However, if the sounds are heard constantly, they signal
a pathologic condition and acquire the properties of real
tinnitus. In these instances, the patient perceives a pulsating
noise in synchrony with his or her heart rate. When this is
present, it needs to be evaluated thoroughly. Vascular noises
usually are caused by turbulences within blood vessels. Narrowing
of blood vessels as well as vascular tumors may cause type
of tinnitus. In addition, other vascular malformations may
result in this type of sound. Since most of the vascular lesions
associated with pulsating tinnitus can be cured by surgical
therapy and since some of the underlying vascular disorders
are potentially dangerous, all cases of pulsating tinnitus
must undergo a thorough medical work-up before treatment is
considered.
MUSCULAR LESIONS
Some patients may experience a clicking noise radiating from
their ear and this can be heard by another person. This can
result in a repetitive type of clicking sound and is due to
contractions of a muscle within the middle ear. These are
involuntary spasms of one of the two muscles attached to the
middle ear bones. There are two muscles in the middle ear:
the stapedius attached to the stapes bone (stirrup) and the
tensor tympani, attached to the malleus (hammer). These muscles
normally contract briefly in response to very loud noise.
Spasms of the eustachian tube muscles normally are restricted
to one side, resulting in click-like sounds. These contractions
do not usually open the eustachian tube, but involve the tensor
tympani muscle. Since this muscle attaches to the malleus,
it thus directionally pulls at the tympanic membrane. Sometimes
one can see the movement of the malleus with the clicking
sound when this occurs. On occasion, one or both of these
muscles may begin to contact rhythmically for no apparent
reason for brief periods of time. Because the muscles are
attached to one of the middle ear bones, these contractions
may result in repetitive sounds in the ear. This clicking
sound, although annoying, is harmless and usually subsides
without treatment. Should this muscle spasm continue, medical
treatment with muscle relaxants or surgery (cutting the spastic
muscle may be necessary).
OPENING MOVEMENTS OF THE EUSTACHIAN TUBE
Opening the eustachian tube occurs by coordinating action
of the two palatal muscles (levator and tensor palatini).
The normal action that opens the eustachian tube and causes
this are swallowing and yawning. Some patients are bothered
by the clicking sound in the ear which accompanies the action
of swallowing and some patients can produce these sounds voluntarily
and elicit this type of noise.
CENTRAL LESIONS
The hearing nerve has approximately 30 thousand fibers within
it. Most of these fibers demonstrate spontaneous activity
and certain sound frequencies are associated with certain
fibers. It is possible that the alterations in this spontaneous
activity may generate tinnitus. It has also been demonstrated
that the auditory nerve is covered by myelin, and it is in
this area that the nerve is more sensitive to vascular compression
by blood vessels in the posterior fossa. It is therefore possible
that the tinnitus may be secondary to a vascular compression
of the auditory nerve. All the fibers of the auditory nerve
end in the cochlear nucleus and each fiber may come in contact
with as many as 75 to 100 cells of the nucleus. There is also
another pathway which is referred to the efferent pathway
which is an inhibitory pathway and may be related to the awareness
of tinnitus. Specifically, tinnitus may be perceived because
of the inability of the efferent system to suppress the tinnitus.
It has been suggested that even though tinnitus may have originated
in the cochlea, retrograde changes may occur within the auditory
pathway and the tinnitus then becomes a central phenomenon.
MIDDLE EAR LESIONS
Any dysfunction of the structure(s) of the middle ear (i.e.
tympanic membrane, ossicular chain problems) can result in
tinnitus. Acute and long-standing inflammation of the middle
ear sometimes will result in tinnitus. Often when the middle
ear abnormalities are corrected by surgery, the tinnitus disappears.
Sometimes in otosclerosis there is an additional component
of tinnitus present, probably of cochlear origin, which is
usually not improved by surgery.
COCHLEAR LESIONS
The cochlea is probably the most common site in the origin
of tinnitus. The inner and outer hair cells are connected
to the central auditory pathway by two systems. Afferent fibers
carry information from the inner ear to the central nervous
system. Efferent fibers from the brain go to the inner ear.
It is felt that abnormalities of the hair cells, efferent
or afferent fiber pathways may give rise to tinnitus.
A SUMMARY OF THE CAUSES OF TINNITUS
Tinnitus may originate from various lesions and from different
sites. The auditory system involves highly complicated inner
ear structures, many afferent and efferent nerve pathways
and a great amount of nuclei that form a complex meshwork.
To pinpoint tinnitus to a certain structure becomes questionable.
This is demonstrated by patients who have had intractable
tinnitus after having surgery on their ear or incurring severe
diseases of the ear. In an attempt to relieve the tinnitus,
cutting the auditory nerve has been done and yet the tinnitus
was persistent, indicating the site of lesion causing the
tinnitus must have shifted into the central nervous system.
Tinnitus could be explained by abnormal neural activity in
the auditory nerve fibers, which may occur if there is a partial
breakdown of the myelin covering of individual fibers. A defect
in the hair cell would trigger the discharge of connected
nerve fibers. For chronic cochlear disorders, there may also
be increased spontaneous activity in the hair cells and neurons
resulting in tinnitus. In the auditory nerve there are two
different kinds of afferent fibers: Inner hair cell fibers
with large diameters and outer hair cells fibers with small
diameters. Thus, loss of signals from the cochlea might trigger
tinnitus as a manifestation of a functional imbalance between
the two sets of fibers. In addition, other abnormal changes
of the cochlear fluids may result in tinnitus.
There is not one type, one site or one origin of tinnitus,
but a multitude of types, sites, and origins. It is also unlikely
that one hypothesis on the cause of tinnitus could explain
all the features.
TREATMENT OF TINNITUS
Generally, most patients will not need any medical treatment
for their tinnitus. For patients who are greatly bothered
by tinnitus, they may use some masking techniques such as
listening to a fan or radio which would mask some of their
tinnitus. In addition, other sound source generators can be
obtained and be adjusted to sound-like environmental sounds
and this is also effective in masking tinnitus. This generally
is more advantageous if one is attempting to go to sleep.
A tinnitus masker is utilized in some patients. It is a small
electronic instrument built into a hearing aid case. It generates
a noise which prevents the wearer from hearing his own head
noise. It is based on the principle that most individuals
with tinnitus can better tolerate outside noise than they
can their own inner head noise.
Biofeedback training is effective in reducing the tinnitus
in some patients. It consists of exercises in which the patient
learns to control the various parts of the body and relax
the muscles. When a patient is able to accomplish this type
of relaxation, tinnitus generally subsides. Most patients
have expressed that the biofeedback offers them better coping
skills.
Other measures to control tinnitus include making every attempt
to avoid anxiety, as this will increase your tinnitus. You
should make every attempt to obtain adequate rest and avoid
overfatigue because generally patients who are tired seem
to notice their tinnitus more. The use of nerve stimulants
is to be avoided. Therefore, excessive amounts of coffee and
smoking should be avoided. Tinnitus will not cause you to
go deaf and statistically, 50 percent of patients may express
that their tinnitus with time decreases or is hardly perceptible.
There are other medications which have been utilized to suppress
tinnitus. Some patients benefit with these drugs and others
do not. Each patient has an individual response to medication,
and what may work for one patient may not work for another.
Some of these medications have been proven, however, to decrease
the intensity of the tinnitus and make it much less noticeable
to the patient. There is, however, no drug anywhere which
will remove tinnitus completely and forever. There are some
drugs which will also cause tinnitus. If you have tinnitus
and are on medication, you should discuss the symptom of tinnitus
with your physician. In many instances, once the drug is discontinued
the tinnitus will no longer be present. |