What is Tinnitus?
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)
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.
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.
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.
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.
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 over fatigue 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.