HEARING LOSS

HEARING LOSS

Hearing Loss is an invisible defficiency. We usually underestimate the importance of hearing in our lives, until it starts decreasing in ourselves.

Hearing is the most important ability to promote the interaction with the world, making human communication to be priceless.

The ear consists of three parts: the external ear, middle ear, and inner ear.
 

	the external ear consists of the pinna and the ear canal with the tympanic membrane located at the end of the canal;
	The middle ear contains three tiny bones, or ossicles, (malleus, incus and stapes) and the eustachian tube opening;
	the inner ear, also called labyrinth, is formed by the vestibular system (balance) and the cochlea (hearing).

A decrease in hearing (deafness) causes a reduction in the perception and comprehension of sound and speech. The difficulty increases with the degree of deafness, which can be mild, moderate, severe and profound.

Levels of Hearing Loss: What does one feel?

People with mild hearing loss may not realize that their hearing is diminishing; only a hearing screening test (audiometry) can detect a hearing impairment. In moderate to severe hearing loss, sounds may get distorted and words will become muffled and harder to understand, during conversation, particularly when there are several people talking in a noisy background environment, or in echo-filled rooms. Doorbells and telephone rings become more difficult to be heard. The hearing-impaired individual keeps asking people to either speak louder or repeat everything they say.

Newborn babies with severe or profound hearing loss never startle at loud sounds. Without proper care, children with hearing disorders will face difficulties developing speech-language; and having reached school age without a proper hearing loss diagnosis can cause these children to have learning difficulties, simply because they poorly hear what is being taught.

In some cases, there are additional symptoms, such as tinnitus and vertigo in the Ménière´s disease. In middle ear infecctions hearing loss is accompanied by pain and fever.

Types of Hearing Loss

Hearing loss may be conductive when there is a blockade of the sound-transmission system, from the external auditory meatus to the limits of the inner ear.

Some important causes of a conductive loss include:
 

	obstruction by wax buildup or objects inserted into the ear canal.
	Perforation or other injury to the eardrum
	middle ear infection
	infection, lesion or fixation of the small bones (ossicles) in the middle ear.

Perceptive or sensorineural hearing loss (lesion of sensory and nerve cells) is caused by some damage to the sound-perception mechanism from the inner ear (cochlea) to the brain.

Some of the important causes of sensorineural hearing loss:
 

	intense noise is a frequent cause of hearing loss; a sound intensity louder than 75 decibels can lead to important noise-induced hearing loss (NIHL). Inner ear lesions can occur either after a single exposure to noise or after a prolonged exposure over months or years. Examples of noises that most commonly cause hearing loss: industrial machinery, firearms, motorcycles, electric lawnmowers, firecrackers, loud music.
	Bacterial and viral infections, particularly rubella, mumps and meningitis.
	Certain drugs, especially some antibiotics, can injure the sensorineural structures and cause hearing loss.
	Aging. Presbyacusis, the gradual loss of hearing associated with aging, is a rather common occurrence in elderly people. Hearing impairment affects about 30% of people over 65 years old, and 50% of people over 75 years old. Presbyacusis is the most common cause of hearing loss and it probably results from a combination of genetic vulnerability, metabolic diseases and/or disorders (e.g., diabetes) and noise exposure. It is a degenerative process of sensory cells in the inner ear and of nerve fibers connecting the brain.
	Congenital hearing loss. When an infant is born with a hearing impairment, it may have been caused by heredity (genetics) or embryonic factors (intrauterine). The most frequent intrauterine-related causes include: rubella, syphilis, toxoplasmosis, herpes, some types of viruses and certain drugs taken by pregnant women.
	Changes in inner ear fluid pressure can lead to a gradual hearing loss, known as Ménière´s disease, which is typically associated with vertigo and tinnitus.
	Benign or malignant tumors affecting the inner ear, or the area between the inner ear and the brain, can cause hearing loss, e.g. acoustic neuroma, cholesteatoma, hemangioma, glomus and carcinoma.

When there is a damage to conductive and perceptive mechanisms, the hearing loss is referred to as mixed hearing loss.

How does the doctor make the diagnosis?

The diagnosis of the cause of the hearing loss is made through the patient´s medical history, ear examination and hearing tests with tuning forks to determine the type of the hearing loss (whether conductive or perceptive). Testing with special equipment may be required in order to perform the hearing assessment, audiometry being the most important one. When dizziness is associated with hearing loss, the labyrinth and the central nervous system are investigated. If a tumor is suspected, Magnetic Resonance Imaging (MRI) may be required.

How does hearing loss evolve?

The evolution of the hearing loss depends on the cause and the severity of the lesion. For instance, if there is a hearing loss due to noise exposures exceeding the tolerated limit (75 decibels), the hearing may be back to its normal condition in 24 hours. However, recurrent exposure can cause permanent damage to the inner ear and, therefore, irreversible hearing loss. Children with middle ear infecction will have fluid buildup behind the eardrum which, in the majority of cases, is absorbed by the organism, and the hearing tends to normalize within a few weeks. Usually, there is a gradual increase in hearing loss in age-related hearing loss (Presbyacusis) and hearing loss caused by the continued use of medication.

How is it treated?

The treatment of hearing loss depends on its cause.
 

	If hearing loss is caused by a large amount of earwax buildup in the ear canal, the physician will simply remove it with special instruments.
	Eardrum perforations and lesions, or fixation of the ossicles (malleus, incus, stapes), should be surgically treated.
	In cases with fluid buildup behind the eardrum (serous otitis) for over 90 days, without hearing improvement, surgery is also indicated.
	In Ménière´s Disease, nonsurgical and, sometimes, surgical treatment is indicated.
	In case of tumor developments, the treatment indicated is essentially surgical, radiotherapeutic or radiosurgical

Many patients with hearing loss may benefit from conventional hearing aids, a device designed to amplify sound.

For those patients suffering from severe or profound hearing loss, who cannot benefit from these devices, a cochlear implant is indicated. Cochlear implants are surgically-implantable eletronic devices, which transmit electrical signals to the brain via the auditory nerve, where they are interpreted as sound.

How is it prevented?

In case of intense noise exposure, hearing loss prevention is managed through collective protection programs (noice sources intervention), or individual protection devices (ear muffs).

Inherited hearing loss prevention is managed through parental genetic-counseling. Prenatal medical care during pregnancy can help prevent the unborn child from a possible hearing loss.

During pregnancy, diseases such as rubella, syphilis and toxoplasmosis, can lead to hearing loss and other abnormalities. Every woman, particularly between the ages of 15 and 35 years old, should be vaccinated against rubella. Vaccination is simple and highly effective. Caution should also be taken regarding taking medication that might be toxic to the child´s ears, administered during pregnancy.

After birth, the child´s hearing can be compromised by certain infectious diseases, such as miningitis, mumps or measles. For these diseases effective vaccination is available. Caution should be taken with certain drugs, particularly some antibiotics that might be ototoxic.

Advances in science and technology enable early diagnosis of infant´ s hearing loss at birth. If something is suspected, immediate medical care is recommended.

A child with a hearing loss should begin treatment early, during the first months.

The earlier the work for the habilitation program for hearing-impaired children begins, by healthcare professionals and parents, the greater the amount of benefit in terms of the child´s language acquisition.

Questions you should ask your doctor

Why am I losing my hearing?

What is causing my hearing loss?

What should I do to improve my hearing?

What should I do to prevent my hearing from getting worse?