- This article is about hearing impairment in the patholocial sense. See deaf culture for deafness in a cultural sense.
Hearing impairment or deafness is decreased or absent ability to perceive auditory information.
While a some cases of hearing loss are reversible with medical treatment, many lead to a permanent disability. Of vital importance are the age at which the hearing loss occurred, as this may interfere with the acquisition of spoken language. Hearing aids and cochlear implants may alleviate some of the barriers caused by hearing impairment, but are often insufficient. Social acceptance and support, as well as technical adaptations, are part of the complicated rehabilitation process of a person with difficulty hearing.
To be deaf is also used by some to refer to a member of Deaf culture.
Causes
There are four major causes of hearing loss: genetic, disease processes affecting the ear, medication and physical trauma.
Genetic
Hearing impairment can be inherited. Both dominant and recessive genes exist which can cause mild to profound impairment. If a family has a dominant gene for deafness it will persist across generations because it will be expressed in the offspring even if it is inherited from only one parent. If a family had genetic hearing impairment caused by a recessive gene it will not always manifest as it will have to be passed onto offspring from both parents.
Dominant and recessive hearing impairment can be syndromic or nonsyndromic. Recent gene mapping has identified dozens of nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness.
- The most common type of congenital hearing impairment in developed countries is DFNB1, also known as Connexin 26 deafness or GJB2-related deafness.
- The most common dominant syndromic forms of hearing impairment include Stickler syndrome and Waardenburg syndrome.
- The most common recessive syndromic forms of hearing impairment are Pendred syndrome, Large vestibular aqueduct syndrome and Usher syndrome.
Disease or illness
- Measles may result in auditory nerve damage
- Meningitis may damage the auditory nerve or the cochlea
- Autoimmune disease has only recently been recognised as a potential cause for cochlear damage. Although probably rare, it is possible for autoimmune processes to target the cochlea specifically, without symptoms affecting other organs. Wegener's granulomatosis is one of the autoimmune conditions that may precipiate hearing loss.
- Presbyacusis is deafness due to loss of perception to high tones, mainly in the elderly. It is considered a degenerative process, and it is poorly understood why some elderly people develop presbyacusis while others do not.
- Mumps (Epidemic parotitis) may result in profound sensorineural hearing loss (91 dB or more), unilateral (one ear) or bilateral (both ears).
Medications
Some medications cause irreversible damage to the ear, and are limited in their use for this reason. The most important group is the aminoglycosides (main member gentamycin).
Various other medications may reversibly affect hearing. This includes some diuretics, aspirin and NSAIDs, and macrolide antibiotics.
Physical trauma
- There can be damage either to the ear itself or to the brain centers that process the aural information conveyed by the ears.
- People who sustain head injury are especially vulnerable to hearing loss or tinnitus, either temporary or permanent.
- Exposure to very loud noise (90 dB or more, such as jet engines at close range) can cause progressive hearing loss. Exposure to a single event of extremely loud noise (such as explosions) can also cause temporary or permanent hearing loss.
Pre- or postlingual
The age at which the hearing impairment develops is crucial to language acquisition:
- Pre-lingual hearing impairment in which the impairment can be congenital, a condition that exists at birth, before the individual has acquired speech and language, thus rendering the disadvantages more difficult to treat because the child is unable to communicate from the outset. Pre-lingual hearing impairment can also be adventitious as in a situation where a child born with normal hearing contracts a disease or sustains an injury that causes hearing impairment, but has not yet acquired a mastery of spoken language. Most pre-lingual hearing impairment is due to adventitious loss.
- Post-lingual hearing impairment where hearing loss is adventitious and develops due to disease or trauma after the acquisition of speech and language, usually after the age of six.
Post-lingual hearing impairments are far more common than pre-lingual impairments. Typically, hearing loss is gradual, and often detected by family and friends of the people so affected long before the patients themselves will acknowledge the disability.
In cases where the causes are environmental, the treatment is to eliminate or reduce these causes first of all, and then to fit patients with a hearing aid, especially if they are elderly. When the loss is due to heredity, total deafness is often the end result. On the one hand, persons who experience gradual deterioration of their hearing are fortunate in that they have learned to speak. On the other, they often experience social isolation, because they can no longer understand their friends, who cannot communicate effectively with them. Ultimately the affected person may bridge communication problems by becoming skilled in speech-reading (lip reading), accepting elective surgery to use a prosthetic devices such as a cochlear implant, using a hearing aid, or acquiring skill in sign language for communication.
In some cases, the loss is extremely sudden. Most often, the cause is unknown. Sometimes, it can be traced to specific diseases, such as meningitis, or to ototoxic medications, such as Gentamicin. In both cases, the final degree of loss varies. Some experience only partial loss, while others become profoundly deaf. In the former case, hearing aids can be used with varying degrees of success, depending on the exact nature of the loss. In the latter, ultimately the affected person will depend on speech-reading and/or sign language for communication.
Partial loss of hearing
People who are hard-of-hearing have moderate amounts of hearing loss but not enough to be considered deaf.
The phrase hard-of-hearing, normally used as an adjective or adverb, can also be used as a noun, referring to people with hearing impairment as the hard-of-hearing.
Hearing impaired persons with partial loss of hearing may find that the quality of their hearing varies from day to day, or from one situation to another or not at all. They may also, to a greater or lesser extent, depend on both hearing-aids and lip-reading. They may perhaps not always be aware of it, but they do admit to it being important to see the speaker's face in conversation.
Many people with hearing loss have better hearing in the lower frequency ranges (low tones), and cannot hear as well or at all in the higher frequencies. Some people may merely find it difficult to differentiate between words that begin with consonantal sounds such as the fricatives or sibilants s, z, or th, or the plosives d, t, b, or p. They may be unable to hear thin, high-pitched or metallic noises, such as birds chirping or singing, clocks ticking, etc. Often, they are able to hear and understand men's voices better than women's.
Others will find their condition so much worse if circumstances in their immediate environment affect the way they are able to use their hearing-aids, or prevent them from employing their lip-reading skills. A room with a high ceiling and a lot of reverberation will affect the sound of a speaker's voice adversely. The position of the listener, too, sitting at a right angle to the speaker at a long seminar table, thus being able to hear only with one, maybe the ineffectual ear, can make a difference. Difficulties can also arise for the listener trying to lip-read, if the speaker is sitting with his back against the light-source and is in this way obscuring his face. A rule of thumb is that bright lighting is to the hearing-impaired what noise is to the hearing; a source of distraction.
The speaker's accent; the topic under discussion, possibly with many unfamiliar words; the softness of his voice; possibly his having a speech impediment; a habit of holding a hand in front of his mouth or turning his face away at times: all these tendencies cause problems to the hard-of-hearing, especially when they have to rely on lip-reading. The rustling of papers, and notebook pages being turned are precisely the noises that will be the first thing hearing-aids pick up.
People with unilateral hearing loss can hear normally in 1 ear, but have trouble hearing out of the other ear.
Profound unilateral hearing loss is a specific type off hearing impairment when one ear have no hearing ability at all. It is known to cause:
- Irritability
- Frequent headaches, stress
- Social isolation
- Trouble figuring out where sounds are coming from.
- Variable light dizziness
- Trouble paying attention in what people are saying: Evasive behaviour.
- Lack of sound depth: any background noise (on the room, on the car) is flat and wronlgy interpreted by the brain. The effect is the same as what happens when normal people try to watch, on a mono TV, someone speaking in a noisy crowd.
- For sensorineural loss, the brain can interpret "ghost beeps" from the lack of input coming from the damaged ear. The frequency and the volume of this beeps varies according to his fisical condition, like stress, being tired, etc. This causes even more irritability and trouble on speech comprehension.
Social impact
Those who lose their hearing later in life, such as in late adolescence or adulthood, face their own challenges. For example, they must adjust to living with the adaptive devices that make it possible for them to live independently. They must also adapt to using hearing aids and/or learning sign language. Loneliness and depression can arise as a result of isolation (from the inability to communicate with friends and loved ones) and difficulty in accepting their disability. The challenge is made greater by the need for those around them to adapt to the person's hearing loss.
Medical treatments
Approaches
In addition to hearing aids there exist cochlear implants of increasing complexity and effectiveness. These are useful in treating the mild to profound hearing impairment when the onset follows the acquisitions of language and in some cases in children whose hearing loss came before language was acquired. Recent research shows variations in effacacy but some promising studies[1] (http://www.cid.wustl.edu/research/PPR/Geers/Geersppr.htm) show that if implanted at a very young age, some profoundly impaired children can acquire effective hearing and speech.
Views of treatments
There is controversy in the culturally deaf community as to whether cochlear implants address wellness concerns, the overall health and psycho-emotional well-being of prelingually deaf chidlren at all.
Adaptations to hearing impairment
Many hearing impaired individuals use certain assistive devices in their daily lives. Individuals can communicate by telephone using telecommunications devices for the deaf (TDD) This device looks like a typewriter or word processor and transmits typed text over the telephone. Other names in common use are textphone and minicom. In 2004, mobile textphone devices came onto the market for the first time allowing simultaneous two way text communication. In the U.S., the UK, the Netherlands and many other western countries there are telephone relay services so that a hearing impaired person can communicate with a hearing person via a human translator. Wireless, internet and mobile phone/SMS text messaging are beginning to take over the role of the TDD. Other assistive devices include those that use flashing lights to signal events such as a ringing telephone, a doorbell, or a fire alarm. Video conferencing is also a new technology that permits signed conversations as well as permitting an ASL-English interpreter to voice and sign conversations between a hearing impaired and hearing person, negating the need to use a TTY or computer keyboard.
Resources
There are many different assistive technologies such as hearing aids available to people who are hearing impaired. There are also Hearing dogs which are a category of Assistance dogs. The advent of the internet's World-Wide-Web and closed captioning has given the hearing impaired unprecedented access to information. Electronic mail and online chat have virtually eliminated the need for hearing impaired people to use a third-party Telecommunications Relay Service in order to communicate with the hearing and other hearing impaired people.
How to communicate
Some guidelines on communicating with a hearing-impaired person:
- Ask the person what will be most useful for them; this varies from one individual to another. Not all items on this list will apply for all individuals.
- Take a class in sign language with the individual along with family and friends. Show your support by striving to master the language.
- Speak normally. Do not shout or over-enunciate. Both of these make it more difficult to understand speech, not less.
- Conversely, do not mumble, cover your mouth, or whisper when speaking. All of these can conceal vital speech-reading cues that hearing impaired people use to decipher what is being said. A "favorite" pet peeve of the hearing impaired is people who speak from another room - How are they to speech-read with a wall between them and the speaker? Additionally, speak while facing the hearing impaired person.
- If asked to repeat yourself, don't. Rephrase instead. By using different words, your friend will be able to use two data sets to understand what you meant. (This is good advice for those with normal hearing, too!) Obviously, if only one word was missed, you can try just repeating that word, or a synonym. This is the area where people vary most: some hearing-impaired people find rephrasing very frustrating, because they have to start over: when a sentence is repeated, they can put together the syllables or words they heard the first time with those in the repetition. When in doubt, ask "Should I repeat that exactly?"
- Emphasize keywords in your phrases. Most hearing-impaired people can piece together keywords (along with the context of the conversation) into a statement that they can understand.
- Reduce background noise by turning off the TV and radio, and closing windows. All of these can provide distractions that cause communication to break down completely. They also impede the perception of whatever auditory cues your friend is able to pick up and use.
- For small children learning to talk, use context to help them decipher what you are saying. (Additionally, some studies indicate that hearing impaired children who are allowed to lead conversation acquire speech much more successfully than those whose parents attempt to guide conversation for them.)
Quotation
- "Blindness cuts you off from things; deafness cuts you off from people." -- Helen Keller
- "What matters deafness of the ear, when the mind hears. The one true deafness, the incurable deafness, is that of the mind." -- Victor Hugo
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