HEAD NOISE OR TINNITUS
Head noise, or tinnitus, is common. It may be intermittent or constant, mild or severe, and vary from a low roar to a high-pitched type of sound. It may be subjective (audible only to the patient) or objective (audible to others). It may or may not be associated with hearing impairment.
Tinnitus must always be though 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, the brain interprets this impulse as noise. This phenomenon is similar to the sensation nerves elsewhere. If one pinches the skin, it hurts because the nerves stimulated carry pain sensation.
Tinnitus may or may not be accompanied by a hearing impairment. Hearing is measured in decibels.
In order to understand the possible causes of tinnitus, one must have some knowledge of the hearing mechanism. This mechanism is made up of five main divisions: the external ear, the middle ear, the inner ear, the nerve pathways and the brain.
The external ear consists of the auricle and the external ear canal. These structures collect the sound waves and transmit them to the eardrum.
The middle ear lies between the eardrum and the inner ear. This chamber contains three ossicles: the malleus, the incus and the stapes (hammer, anvil and stirrup). Vibrations of the eardrum are transmitted across the middle ear space by these three small ear bones. Movement of the third bone (stapes or stirrup) results in fluid waves in the inner ear.
The middle ear chamber is lined by a membrane similar to the lining of the nose and contains secreting glands and blood vessels. This chamber is connected to the back of the nose by a small channel called the eustachian tube.
The eustachian tube serves to maintain equalization of pressure between the middle ear chamber and the outside atmosphere, as evidenced by the popping sensation noted in the ear during altitude changes.
The inner ear is enclosed in dense bone and contains fluid and the tiny hearing cells. It is lined by a delicate transparent membrane supplied by microscopic blood vessels. In this small chamber, fluid waves resulting from movement of the stapes are transformed into electrical impulses in the nerve.
The electrical impulses created in the inner ear chamber are transmitted to the brain by the hearing nerve. The nerve pathways leading to the brain are enclosed in a small boney canal along with the nerve of balance and the nerve which stimulated movement of the facial muscles.
The hearing nerve pathways divide as they reach the brain into an inter-communicating system far more complex than the most extensive telephone exchange. Nerve impulses are then transformed into recognizable sound.
Most tinnitus is audible only to the patient; this is called subjective tinnitus. Tinnitus audible to both the patient and others is called objective tinnitus, the least common form.
Objective tinnitus may be due to muscle spasms in the middle ear or eustachian tube or be due to abnormalities in the blood vessels surrounding the ear.
Tinnitus may result from spasm of one of the two muscles attached to the middle ear bones or from spasm of muscles attached to the eustachian tube, the channel which connects the middle ear to the back of the nose.
There are two muscles in the middle ear: the stapedius, attached to the stapes bone (stirrup) and the tensor tympani, attached to the malleus bone (hammer). These muscles normally contract briefly in response to very loud noise or as a result of a startle reaction.
On occasions one or both of these muscles may begin to contract rhythmically for no apparent reason, for brief periods of time. Because the muscles are attached to one of the middle ear (hearing) bones these contractions may result in a repetitious sound in the ear. The clicking, although annoying, is harmless and usually subsides without treatment.
Should the muscle spasm continue, medical treatment (muscle relaxants) or surgery (cutting the spastic muscle) may be necessary.
Muscular tinnitus resulting from spasm from one of the various muscles of the throat attached to the eustachian tube is uncommon, but can also result in episodes of rhythmic clicking in the ear. This is called palatal myoclonus and usually responds to muscle relaxants.
There are two large blood vessels intimately associated with the middle and inner ear: the jugular vein and the carotid artery. These are the major blood vessels supplying the brain.
It is not uncommon to hear one’s heart beat or to hear the blood circulating through these large vessels. This may be particularly noticeable when an individual has a fever or a middle ear infection, or after engaging in strenuous exercise. The circulation sound in these instances is temporary and is not audible to others.
On occasions the sound of blood circulation will become audible to others. This can be due to thickening of the blood vessel wall (a normal occurrence as one grows older), a kink in the vessel or an abnormal growth on the vessel wall. Further testing may be necessary to determine the cause and treatment indicated in these uncommon cases.
Obstruction of the external ear canal by wax, foreign bodies or swelling may produce a hearing impairment or pressure on the eardrum. This frequently results in a pulsating type of tinnitus.
Disturbances of function of the middle ear may result from allergy, infection, injury, scar tissue or impaired motion of the three middle ear bones. These disturbances often result in hearing impairment and may lead to head noise. But there is no relationship between the degree of hearing loss and the intensity of the tinnitus.
Any condition which disturbs the fluid pressure in the inner ear chamber may produce head noises. This may be due to infection, allergy, or circulatory disturbances which produce changes not only in the fluid but also in the encasing membranes of the inner ear.
The nerve pathways are the most delicate structures of the hearing mechanism. The small hair cells which serve to transform fluid waves into nerve impulses are analogous to the cells of the eye retina which transform light waves into nerve impulses. The slightest swelling or interference with these delicate cells from any cause readily produces impairment of function and irritation. This may occur from a variety of causes: infection; allergic swelling; systemic diseases, either acute or chronic, with resultant toxic effects; sudden exposure to a blast of sound or prolonged exposure to high noise levels in susceptible persons; certain drugs to which the patient may be sensitive; and minute changes in the blood supply with resultant changes in nutrition.
Inflammation and pressure changes may produce swelling both from outside and within the nerve as it transverses the boney tunnel through which it passes to the brain. Various viral particles may cause inflammation in the hearing nerve without any symptoms of a flu-like illness. In these instances, the tinnitus occurs on one side of the head and because the boney tunnel cannot expand with the pressure phenomenon, not only the function of the hearing nerve, but also the balance and facial nerves may become disturbed as they pass through this boney tunnel.
Interference of circulation in one of the small blood vessels occurring anywhere in the auditory pathway produces altered function. Consequently, sudden tinnitus, with or without partial or total loss of hearing function, may occur. If the circulatory change is minor, it may resolve with little or no permanent change. This condition, like the pressure phenomenon, occurs only on one side, and because it has occurred once doesn’t mean it would necessarily occur again on the same or opposite side.
Any disturbance, whether due to swelling, pressure or interference with circulation, may occasionally involve one or more of the complex hearing pathways as they enter and terminate in the brain. In this instance, the brain can produce head noise or tinnitus. At times, head noise or tinnitus which has begun within the inner ear or along the hearing nerve, may change such that the sensation occurs from the within the brain. In these instances, the tinnitus may be perceived as a diffuse sensation within the whole head.
Head noise or tinnitus may or may not be associated with hearing impairment. After reviewing the many causes of this symptom, it is easy to understand why the hearing may at times be affected when tinnitus is present. If a hearing loss coexists with tinnitus, the severity of the head noise is not an index as to the future course of the hearing impairment. Many persons with tinnitus have the erroneous fear they are going to lose their hearing. This is an unnecessary fear.
Physical or emotional stress is present in everyone’s life periodically. In some, it is chronic, and can result in symptoms of depression. At times, a symptom such as tinnitus may, in itself lead to depression. This can make the tinnitus more bothersome. A vicious cycle may develop involving depression and symptoms of tinnitus in which both are aggrevated by the other.
At times, we may recommend that a patient with severe tinnitus be treated with antidepressants or antianxiety medications. Patients of this type are also the ones who are most likely to benefit from biofeedback treatment.
The auditory (hearing) pathway is one of the most delicate and sensitive mechanisms of the human body. Tinnitus or head noise may result from a variety of disturbances within the ear, its neural pathways and the brain. In order for any treatment of tinnitus or head noise to be successful, it is imperative that the patient have a thorough understanding of this distressing symptom complex. With proper medical care, tinnitus and head noise can be controlled in most patients.