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Hearing Loss - What is Hearing Loss?

Age related illnesses | August 18, 2014 | Author: The Super Pharmacist

ENT, ear

Hearing Loss - What is Hearing Loss?

Hearing loss is not a technical term and it is just what it says. It is the inability to perceive sound normally. There is no cut-off value, before which there is perfectly normal hearing and beyond which comes absolute deafness.

Hearing loss always occurs in degrees. The unit for loudness (intensity) of sound used in clinical practice is the decibel (dB). A normal conversation occurs at 60 dB and a whisper is around 20 dB. Noise greater than 85 dB will eventually damage hearing.

Degree of Hearing Loss

The degree of hearing loss is judged in comparison to what is set as normal hearing. Increasingly impaired hearing will present as the following degrees of hearing loss:

  • Mild
  • Moderate
  • Severe
  • Profound

How Common is it?

Hearing loss is much more common than you might have anticipated. National estimates indicate that around 10% of Australia’s population is affected by partial or complete hearing loss. About a third of these have noise-induced hearing loss which makes that the most common cause of impaired hearing. Another frequent cause is presbycusis, which is what age-related hearing loss is called. Almost a third of people between ages 60 and 70, and almost half of those above 70 have hearing deficits.

Hearing loss is one of the most frequent reasons people seek medical advice. All this makes it important to understand its causes and treatment options. It will be easier to look at the causes of hearing loss if we have some idea of the mechanism of hearing.

Mechanism of Hearing

  • External Ear - Collects sound waves 
  • Tympanic Membrane 
  • Middle Ear - contains 3 tiny bones that helps transmit sounds to the
  • Internal Ear - the sensory organ is spiral, like the shell of a snail and is called the cochlea; it contains the hair cells and sensory nerves.
  • Auditory Nerve 
  • Brainstem 
  • Auditory Centres of the Brain - where sound interpretation occurs

Causes and Types of Hearing Loss

Treatments of Specific Causes

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If components of both types of hearing loss are present then it is referred to as mixed hearing loss.

Symptoms of Hearing Loss

Many people with mild to moderate hearing loss may actually be unaware that they suffer from the condition. This is because hearing loss is generally a gradual process occurring over months to years, which gives people time to adjust and makes it difficult for them to realise that a deficit is developing. It is important therefore to know signs of deteriorating hearing:

  • Difficulty hearing in noisy surroundings
  • Frequently asking people to repeat themselves
  • Difficulty hearing high-pitched voices, such as those of women and children
  • Trouble conversing over the phone
  • Confusion when two or more people are talking at the same time
  • Perception that people are mumbling
  • Misunderstanding what someone has said
  • Buzzing, hissing or ringing sounds in the ear

Diagnosis

Symptoms of Hearing LossIf you have experienced any of these symptoms or if you have noticed them in someone close to you, a medical checkup is advised. Immediate help will be available with your family doctor or local general practitioner, who can do an initial hearing assessment and try to look for clues in the history and physical examination.

Depending upon his/her analysis, further hearing tests and investigations may be recommended. You may also be referred to an ENT doctor specialised in the management of ear problems. Such a specialist is known as an otologist.

Investigations

Two relevant investigations are audiometry4 and tympanometry. An audiometer will check both the degree of hearing loss (in decibels) and the frequencies over which this loss has occurred. A tympanogram will show any problems with the tympanic membrane (eardrum).

Management

Management begins once the degree and nature of hearing loss has been established. If a well-defined cause or aggravating factor is identified, it has to be treated accordingly before managing the hearing loss itself. Treatment options for some specific causes have been shown above. A person with hearing loss, for whom nothing further can be accomplished through medications or surgery, will be a candidate for hearing aids. This is usually the case with presbycusis and noise-induced hearing loss, both of which typically cause gradual permanent sensorineural hearing loss. Some other helpful measures include:

  • Telephone amplifying devices
  • Instant messaging software
  • Videophones
  • Alerting devices
  • Sign language

Hearing Aids

Hearing AidsWhen it has been determined that a hearing aid is needed, you will most likely be referred to an audiologist who will help you to choose and use a suitable hearing aid.

The technology that hearing aids are based on is either digital or analogue. Digital hearing aids are the latest devices and offer more advantages than analogue types. They are programmable and customisable.They are replacing analogue devices.

Hearing aids come in different shapes and sizes.

  • Behind-the-ear (BTE) aids: The hearing aid rests behind the ear, connected to a smaller earpiece. These are sturdy and the earpiece can be replaced in growing children.
  • In-the-ear (ITE) aids: The hearing aid rests in the ear canal and a bit outside it. It is more visible than an ITC or CIC hearing aid.
  • In-the-canal (ITC) aids: The hearing aid fits into the ear canal and is just visible outside.
  • Completely in-the-canal (CIC) aids: The hearing aid is located within the ear canal and is barely visible outside.

For people with conductive hearing loss and in whom conventional hearing aids are not effective, hearing aids based on bone conduction are considered.

  • Bone conduction hearing aids: These are worn around the head and conduct sound through a bone behind the ear, which is called the mastoid.
  • Bone-anchored hearing aids (BAHA): The anchor (screw) is attached to the mastoid during a minor surgery. The hearing aid can be clipped on and off.

Cochlear Implant

For adults and children with severe to profound sensorineural hearing loss that will not benefit from hearing aids, a cochlear implant is an option.

A cochlear implant is placed surgically. A receiver placed under the skin behind the ear receives signals from an external processor. It then sends those signals along a wire all the way to the auditory part of the internal ear.

A cochlear implant is expensive and it requires careful candidate selection and training to be successful. Hence it is not recommended for everyone with a hearing impairment.

Experimental Treatment Options

  • Latest research for the restoration of hearing is focusing on the possibility of converting stem cells into hair cells for the human ear. Damage to these hair cells leads to sensorineural hearing loss. The results in animals are promising.
     
  • A hybrid auditory device which resembles a cochlear implant, but is indicating better results, is in the pipeline.
     
  • Ginkgo biloba leaf extract and soluble coenzyme Q10 are being studied for their apparently beneficial effects in improving sensorineural hearing deficit.

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References

Curhan SG, Eavey R, Shargorodsky J, Curhan GC. Analgesic Use and the Risk of Hearing Loss in Men. The American Journal of Medicine. 2010;123(3):231–237.

Havia M, Kentala E, Pyykkö I (2002). Hearing loss and tinnitus in Meniere’s disease. Auris Nasus Larynx 29: 115-119.

Andersen H, Schrøder S, Bonding P. Unilateral deafness after acoustic neuroma surgery: subjective hearing handicap and the effect of the bone-anchored hearing aid. Otol Neurotol. 2006;27(6):809–814.

Pittman AL, Stelmachowicz PG. Hearing loss in children and adults: audiometric configuration, asymmetry, and progression. Ear Hear. 2003;24:198–205.

Abdulrahman H. BAHA: bone-anchored hearing aid. Int J Health Sci (Qassim) 2007;1(2):265–276.

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