Disease 101: Audiograms and Related Diseases

2014 / 08 / 15  |  
Prevent hearing loss

Reminder: The information provided below is for your reference only. Please schedule a further hearing check-up at a hospital if necessary.

There are two kinds of audiometry tests to measure sound conduction. The first one is air-conduction hearing test, where the test takers are required to wear earphones/headphones. Air-conduction hearing is when sound waves travel from the outer ear, through the middle ear to the inner ear before sounds are further processed. The second one is bone-conduction hearing test, during which a special vibrator is placed at the mastoid behind the ear. The bone conduction hearing is when sound vibrations travel directly to the inner ear without going through the outer ear and the middle ear.

The online hearing test provided by Erdo only offers results for the hearing threshold of the air-conduction pathway. As a result, the audiogram will show possible signs of a hearing loss if any part of the air-conduction pathway goes wrong. When you have possible signs of a hearing loss, however, you should consult a doctor and take air-conduction and bone-conduction hearing tests as well as other further hearing check-ups so that you can identify the real causes.

AudiogramRelated disease
The falling configuration
(high frequency hearing loss)
The rising configuration
(low frequency hearing loss)
The flat configuration
The asymmetric hearing loss
The mid frequency hearing loss
The high frequency and low frequency hearing loss

(1) Tinnitus

Tinnitus is the perception of sound without an external cause. Most cases of tinnitus are subjective. Subjective tinnitus is tinnitus only you can hear. The sounds that each patient hear may vary from frequencies of insect sounds, whistles, bell rings, to ocean sounds, and they could be continuous, intermittent, or pulsatile.

There are many possible causes for subjective tinnitus. Sometimes even people with normal hearing can have tinnitus. People often hear tinnitus when they are in an extremely quiet environment. If you ask your friends and family members, you'll find that most of them may have had tinnitus.

Many people with hearing loss suffer from tinnitus. After a long time exposure to high intensity of noises such as sound of gun shots or that of firecrackers, people may experience tinnitus. Normally, it goes away after a few hours or days of rest, but some people may never recover from it ever since.

Usually, tinnitus does not influence our daily life, and it can be decreased as long as we stay in a good mood and have a good night's sleep. You should, however, be really careful if the tinnitus gets louder during a short period of time, occurs in only one ear, or goes hand in hand with symptoms such as vertigo and hearing deterioration. Consult a doctor immediately if you have these symptoms, as they may be the symptoms of nasopharyngeal carcinoma, acoustic neuroma or sudden hearing loss.   top  

(2) Presbycusis

Presbycusis is the loss of hearing that gradually occurs in most individuals as they grow older. Those with severe signs of presbycusis would turn the TV volume louder and louder, ask people to speak louder, complain that people aren't speaking clearly, and so on.

It is noteworthy that presbycusis does not suddenly happen when people get old. The age-related hearing deterioration often starts when people are still young. It is difficult to identify the problem at its early stage because the deterioration starts from extremely high frequencies. Generally, children can hear sounds at up to 20,000 Hz. As they grow older, however, they can only hear sounds at 12,000-14,000 Hz, and some may only hear sounds at 10,000 Hz. Nonetheless, human voice frequency is generally less than 8,000 Hz. It is why people don’t usually notice such hearing deterioration, which, in fact, is happening every day.

The influence of presbycusis on both ears goes at the same rate of speed. Presbycusis is a type of sensorineural hearing loss, resulting in patients’ decreasing auditory discrimination ability or complaints about not being able to hear sounds clearly. If an ear has a more severe hearing loss than the other, the patient should look into other causes for the hearing loss.

It is generally accepted that the aging of ears is the significant cause for presbycusis, and that our age is the main culprit. Arteriosclerosis, noises, drug use, and other influencing factors are considered to increase presbycusis. Our genes also play a major role in the development of presbycusis.

There is currently no treatment for presbycusis. Using hearing aids may help improve hearing if the hearing loss is larger than 35 dB HL at human voice frequency. Although hearing aids have limited ability to improve decreased auditory discrimination caused by presbycusis, it puts the pressure off the user by reducing listening fatigue.   top  

(3) Noise induced hearing loss, NIHL

Excessive noise exposure could lead to temporary or even permanent hearing loss.

The different hair cells inside the cochlea either regulate sounds or transfer sounds to neural signals. Noises can pose a great threat to these hair cells. Excessive noise exposure places a great burden on hair cells, and, in turn, makes them easily fatigue, resulting in a temporary threshold shift. Generally speaking, a temporary threshold shift may be restored after adequate rest and relaxation. Exposure to noises over a long period of time can cause permanent damage to hair cells and hearing.

The international noise standard is that human beings should not be exposed to the sound level of 90 dBA (equivalent to traffic noises during the rush hour) for more than eight hours, or the risk of NIHL may occur. The allowed exposure time decreases by half for each 5 dBA increase in the average noise level. For instance, exposure is limited to 4 hours at 95 dBA and 2 hours at 100 dBA.

NIHL is different from presbycusis in that NIHL usually affects hearing at frequencies at 3,000, 4,000 and 6,000 Hz, whereas presbycusis often starts affecting hearing at 20,000 Hz. A typical audiogram of NIHL shows a configuration of a valley where the curve is higher at both ends and lower in the middle. The patient’s hearing at frequencies higher than 8,000 Hz is still normal, and their hearing age is no different from the actual age.

The criteria for examining the risk of exposure to dangerous noise levels is: having to raise your voices, not being able to hear people's speech even at a distance of one meter, still having tinnitus or otalgia (earache) after getting away from the exposure, and so on. Try to stay away from noises and keep the music volume low in order to prevent NIHL.   top  

(4) Sudden sensorineural hearing loss

SSNHL is also commonly known as “ear stroke.” People with SSNHL usually experience sudden hearing deterioration, aural fullness, or tinnitus getting louder. The clinical definition of SSNHL is hearing loss of at least 30 dB in 3 sequential frequencies for three days. It can happen to any age group, especially the age group of 50-60. Around 90% of the patients suffer from unilateral SSNHL.

The causes of SSNHL vary widely, including viral infections (some patients develop upper respiratory tract infection such as flu and measles within a month); vascular diseases (the auditory dysfunction caused by insufficient blood supply to the inner ear is usually the result of systemic vascular diseases such as hypertension and hyperlipidemia); and others like autoimmune diseases, tumor, etc. As a matter of fact, only 10-15% of the patients can be identified with the causes.

If you discover that your hearing is deteriorating, consult a doctor immediately. If you can receive treatments within a week after the problem is detected, the possibility of hearing recovery is higher.   top  

(5) Perforation of the tympanic membrane

The tympanic membrane (eardrum) is a thin membrane that separates the external ear from the middle ear. The sound waves from the air are transmitted through the vibration of the eardrum.

The perforated tympanic membrane is sometimes caused externally when a person is slapped on the face, exposed to explosion sounds, or contused during ear wax cleaning. The perforation is caused by the enormous pressure on the tympanic membrane or foreign material intrusion. The symptoms of perforated tympanic membrane include sudden hearing loss and extra pressure in the ear.

Another possible cause for the perforated tympanic membrane is otitis media. The repetitive inflammation of the middle ear could lead to tympanic erosion. If the perforation is caused by acute otitis media, the patient may experience hearing loss as well as otalgia (earache) and otorrhea (ear discharge), both of which may not occur in the case of chronic otitis media.

A slight perforation of the tympanic membrane may heal itself naturally, with a healing rate of higher than 80% for small perforations. You should, however, consult an ENT doctor if you don't really know how bad the perforation is.   top  

(6) Meniere's disease

If you have had more than 20 minutes of vertigo, tinnitus, aural fullness, and fluctuating hearing loss, the chances are that you may have Ménière's disease. It is also called endolymphatic hydrops, which occurs when the membranous labyrinth of the inner ear shows hydrops. The membranous labyrinth includes the vestibule that controls the body balance and the cochlea that controls the hearing. As a result, patients with labyrinthine hydrops generally feel dizzy and have hearing problems.

The vertigo attacks, accompanied by nausea and vomiting, usually last from 20 minutes to several hours. The attacks are unpredictable and recur after symptom-free intervals. On the other hand, the intensity of tinnitus would increase before and during the attack, with concomitant aural fullness. While the hearing loss is mainly sensorineural hearing loss at low frequencies, it is also accompanied by a decrease of sound intelligibility. On average, the patients with Ménière's disease usually have their first attack during their forties, but it could still have happened to anyone at any age.

The causes of Ménière's disease are still unknown. Some doctors believe that it’s the patient’s stress that triggers autoimmune disorders. Other doctors believe that the contribution of the upper respiratory tract infection made to the intrusion of viruses or bacteria into the inner ear causes the endolymphatic sac occlusion or abnormal endolymph circulation, resulting in labyrinthine hydrops.

Through medication, the number of Ménière's disease attacks can be lowered. Those with vertigo and severe hearing loss can undergo surgery or inject gentamicin into the middle ear to put an end to the troubles caused by vertigo, but these treatments may often cause harm to hearing, even deafness. Doctors suggest that patients with Ménière's disease should avoid intakes of high salt, caffeine, nicotine, and chocolate in order to reduce the possibility of labyrinthine hydrops. On the other hand, finding ways to relieve stress in life is also a good way to control the disease.   top  

(7) Impacted cerumen

When excess cerumen (ear wax) blocks the ear canal, which affects sound conduction in the ear, our hearing is hindered. This is a kind of conductive hearing loss. As the ear canal is occluded, our hearing may drop by 45 dB at best. After a swim or a bath, cerumen swells upon absorption of water and blocks the ear canal completely, resulting in sudden hearing loss. When that happens, you should go to the doctor.

Nonetheless, cerumen buildup and blockage often happens not because people do not clean their ears but because they do. This only pushes the cerumen that is supposed to move out of the ear by motions farther into the ears.

Most ENT doctors suggest that people should not clean ear themselves. Cotton swabs or bobby pins aren’t right for the job because they only push the ear wax farther into the ears and can also cause injury to the ear canal, causing inflammation and infection. If your ears are feeling weird that you think your hearing has been affected, you should probably consult an ENT doctor for better treatments.   top  

(8) Otitis media

Otitis media refers to the inflammation of the middle ear caused by viral or bacterial infections. Otitis media is often found among children. According to statistics, 70-80% of children have had otitis media at least once before turning three.

Why does our middle ear get inflammatory so easily? Many people think that it’s caused by tiny foreign objects going from the ear canal to the middle ear. However, the main reason is that the middle ear is connected to the nasopharynx (the upper part of the throat behind the nose). When the respiratory tract is infected by flu, sinusitis, or allergic rhinitis, bacteria and viruses can easily get into the middle ear through the Eustachian tube and cause infections.

There are three types of otitis media: acute otitis media, serous otitis media, and chronic otitis media:
(1) Symptoms of acute otitis media include: earache, fever, and sometimes effusion.
(2) Serous otitis media happens after the acute otitis media when the clear fluid that stays in the middle ear turns gooey and thick. This presents a problem for sound wave conduction along the auditory pathway.
(3) Chronic otitis media is otitis media that persists more than 12 weeks, and it’s usually accompanied by the perforation of the tympanic membrane.

Conductive hearing loss is one of the common symptoms of otitis media because the fluid and pus in the middle ear or the perforated tympanic membrane make the sounds muffled. With proper treatment, hearing can be restored after the fluids are removed and the tympanic membrane fixed. Without proper care, the repetitive otitis media could result in the erosion of auditory ossicle and cochlea, causing a permanent hearing loss (a mixed hearing loss).   top  

(9) Otosclerosis

Otosclerosis is a disease found at the junction of the ossicular chain and the cochlea in the middle ear, and it often occurs in the stapedial footplate and the oval window. As the spongy bone tissue grows around the junction, the conduction efficiency is lowered, resulting in the gradual hearing loss.

The disease can be considered to be hereditary that runs in the family. In addition, the incidence rate of women is the double of that of men. Pregnancy also increases the severity of the disease. The age of onset is at 20-40 years old.

In the early stages, a gradually progressive low-frequency conductive hearing loss is first seen, while the speech recognition is still normal. Despite the gradual hearing loss, the patient may also experience tinnitus. As the disease progresses, the configuration on the patient’s audiogram may evolve into the flat hearing loss, meaning poor air conduction thresholds at every frequency. Some patients’ cochlea may also be affected by the disease, resulting in the sensorineural hearing loss.

Patients with otosclerosis usually receive surgery by implanting a tiny prosthesis into the middle ear to replace the hardened ossicle. In light of medication treatments, a study (Shambaugh & Causse, 1974) has indicated that sodium fluoride helps 80% of the patients relieve the progression of their diseases. Those who are unable or unwilling to have surgery can wear hearing aids to improve their hearing.   top  

(10) Vestibular schwannoma/acoustic neuromas

Vestibular schwannoma is also called acoustic neuromas, a benign tumor caused by the schwann cells surrounding the vestibular nerve. It's a benign tumor that grows at a low speed. If the tumor continues to grow, however, it will suppress other cranial nerves and lead to other serious problems. If located in the internal auditory meatus, it would suppress the auditory nerve or the vestibular nerve. If located outside the internal auditory meatus (the cerebellopontine angle, for example), the tumor would suppress the facial nerve, trigeminal nerve, or brainstem. At worst, it could be fatal.

The disease is difficult to be detected at its early stage, which is basically hearing-related symptoms including tinnitus, gradual unilateral hearing loss, or sudden hearing loss mainly at high frequencies. Vestibular symptoms are also quite common. Patients may experience vertigo, imbalance, and unsteady gait. If the tumor has suppressed the facial nerve, patients may experience unilateral facial numbness.

Once you find unparalleled hearing loss, tinnitus, vertigo, unsteady gait, or facial paresthesia, you should schedule an appointment with the doctor to see if you have vestibular schwannoma.   top  

(11) Cholesteatoma

Cholesteatoma is also called pearl tumor because of its pearl-like color, but it isn't a type of tumor. Cholesteatoma results from the keratinization of squamous epithelium that causes the abnormal collection of skin cells and keratins in the middle ear. Together these keratins could be erosive.

The reason for the keratinization of squamous epithelium in the middle ear is sometimes due to the eardrum rupture caused by otitis media. Sometimes dysfunction of the auditory tube leads to the imbalance of pressure in the middle ear, and the constant state of negative pressure would pull the eardrum (usually the upper pars flaccida) towards the middle ear. As the pull causes a rupture, the squamous epithelial cells migrate into the middle ear cavity from the outer auditory canal.

The development of cholesteatoma is slow. Normally, no evident signs would be observed, but the possible concomitant bacterial infection would lead to effusion and earache. As mentioned above, cholesteatoma is erosive, so it starts the invasion into peripheral organisms such as the ossicle, semicircular canals, or cochlea after it has grown to a certain state, causing hearing loss or vertigo. As cholesteatoma can also affect the facial nerve that passes the middle ear, it can also contribute to facial nerve paralysis. If the cholesteatoma spreads to the mastoid behind, it could invade the bottom of the brain, causing meningitis, cerebritis, etc.

As indicated by the aforementioned reasons, the hearing loss caused by cholesteatoma can be conductive or mixed hearing loss. The main treatment for cholesteatoma is to have removal surgery.   top  

(12) Ototoxicity

Some drugs may cause temporary or permanent hearing loss.

Drugs that may cause temporary hearing loss include: painkillers containing salicylates (aspirin, for example), Quinine for malaria, loop diuretics for heart diseases and kidney diseases, etc.

Drugs that may cause permanent hearing loss include antibiotics containing aminoglycoside such as gentamicin for bacterial infections, which causes hearing loss for patients with certain genes; and some chemotherapy drugs such as cisplatin and carboplatin.

There are quite a number of ototoxic drugs. Please see a doctor to understand how a certain medication will affect your body if, after your medication, you develop hearing or balance-related problems such as hearing deterioration, tinnitus, vertigo and so on. Patients prescribed with these medications should understand that these medications are still required in some cases, and that the doctor must have taken into account the nature and severity of their disease before writing the prescription. People using these medications should follow up on their hearing conditions regularly.   top  

(13) Hypertension, hyperlipidemia, and diabetes mellitus

Triple H (high blood pressure, high cholesterol, and high glucose) not only poses threats of cardiovascular diseases but also hinders hearing.

Our inner ear relies heavily on the supply of oxygen and blood to function. Our inner ear is also where the blood vessels of cochlea are distributed. Once a branch of blood vessels is clogged, there is hardly any other blood vessel that can assist with blood supply. The triple H often causes cardiovascular diseases such as hardening blood vessels and clogged blood vessels. These cardiovascular diseases influence the blood supply to the cochlea, causing nutritional deficiency that leads to the death of hair cells. The insufficient blood supply to the auditory nerve would lower the patient's ability to hear sounds clearly.

To sum up, if you have the triple H, you must listen to your doctor and control your blood pressure, cholesterol, and blood sugar in order to prevent the complications of cardiovascular diseases.   top  

(14) Congenital hearing loss

Some babies have hearing loss before birth. In Taiwan, 3 out of 1,000 newborn babies have sensorineural hearing loss, excluding the conductive hearing loss such as otitis media. 50% of these babies are genetically predisposed to hearing loss, while others may be affected by environmental or unknown factors. Currently, hearing loss-related genes like Connexin 26 can be identified in genetic screening during pregnancy.

About 30% of the genetically inherited hearing loss takes the form of syndromes. Some of the common examples include Pendred syndrome characterized by goitre, Usher's syndrome characterized by retinitis pigmentosa, and Waardenburg's syndrome characterized by a patch of white hair and blue eyes.

Not all congenital hearing loss is hereditary. During the pregnancy, the development of the fetus may go wrong, resulting in deformations such as microtia. Other causes of congenital hearing loss could be viral infections from mother to baby during pregnancy such as rubella virus and cytomegalovirus (CMV). If a pregnant woman uses ototoxic drugs, her baby's hearing could also be hindered.

Some hearing-related diseases including presbycusis, NIHL (more prone to be affected by noises), Ménière's disease, and otosclerosis have been observed to be hereditary in the family.   top  

(15) Inspections

Why is the test result unsatisfactory when you think you have a good hearing? It could be the improper use of the equipment or test method that’s causing the problem.

Please read the following instructions and check again before you take the test.

(1) Use your earphones/headphones during the test. We suggest that you use hardware that has been sound calibrated.
(2) Make sure that the volume of both sides of the earphones/headphones is normal. Please use one ear to listen to both sides to see if the quality and the volume is equal.
(3) Stay away from noises and take the test in a quiet indoor environment like the library.
(4) Turn off or stay away from the source of noises that are easily neglected. For example, air-conditioning system, electronic fan, personal computer, TV, dehumidifier, refrigerator, etc.
(5) Make sure that you take the test at your best mental condition. Fatigue and lack of focus may also sabotage the test result.

If the test result is still very different from what you have expected, please contact us and tell us what you have encountered via erdo.inc@gmail.com . We will try to identify possible disturbance for you to maximize the accuracy of the quick screening test.   top  

(16) Enlarged vestibular aqueduct

If you bump your head and find later that your hearing has dropped, it could be the enlarged vestibular aqueduct syndrome.

The vestibular aqueduct is a bony canal full of endolymph and connects the inner ear to the brain. Inside the inner ear, the auditory and vestibular receptors are soaked in the endolymph. The enlargement of vestibular aqueduct would lead to the abnormal pressure and metabolic anomaly of the endolymph, causing hearing problems and vestibular anomaly.

The disease is also called the large vestibular aqueduct syndrome, which is a congenital condition. The hearing loss usually manifests itself during the patient's childhood, but some people are not identified with the hearing loss until puberty or adulthood. The hearing loss takes two forms: gradual hearing loss and sudden hearing loss of more than 15 dB. The reason behind the hearing change is due to recent activities which cause the intracranial pressure to increase including flu, intense exercise, head bumps and taking flights. Such activities cause bad hearing from time to time, which is referred to as fluctuating hearing. The cumulative results of these activities also lead to permanent hearing loss.

As a result, doctors often advise their patients to watch out for head injuries and avoid high-intensity exercises and activities. As the vestibule is responsible for balance of the body, 1/3 of the patients have had vertigo, and some patients have experienced other balance difficulties such as dizziness and vomiting.

Currently, surgery and medication are the two main treatments. In addition, patients with a hearing loss can use hearing aids and even have a cochlear implant to improve their hearing.   top  

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