Deafness

Models of deafness

Various models of deafness are rooted in either the social or biological sciences. These are the medical or infirmity model, the social model, and the cultural model. The model used affects how deaf persons are treated and their identity. In the medical model, deafness is viewed an undesirable condition, to be treated. Within the social model, the design of the deaf person's environment is viewed as the major disabling factor. In the cultural model, the Deaf belong to a culture in which they are neither infirm nor disabled.

Physicians and scientists are often labeled as adherents of the medical model by Deaf individuals, who contrast it with their own, cultural model. However, many of those who are labeled so dispute the validity of the label. The social model seeks to illuminate the difficulties that deaf individuals face in their social environment.

The medical model of deafness is viewed by advocates for the deaf as originating from medical, social welfare and majority cultural notions of the absence of the ability to hear as being an illness or a physical disability. It stems from a more comprehensive and far-reaching medical model of disability. People who experience hearing loss after acquiring a mastery of spoken language usually identify with this model. Also, people who describe themselves as hard-of-hearing or hearing impaired are likely to identify with it.

Medical ethics and law dictate that it is up to the patient (or his legal representative) to decide the treatments she or he wishes. For this very reason, the question as to whether deafness is physical impairment or personal tragedy to be overcome is secondary to medical doctors and health professions. Similarly, doctors and scientists who engage in research are doing so simply because there is demand for information and for techniques which can restore hearing.

The view that deafness is a disability has economic consequences in political environments concerned with social welfare. It is the basis on which the governments in many developed countries provide financial support for the cost of cochlear implants and other therapies. It is also the basis on which governments provide deaf people with financial support and educational services which aren't available for members of other cultural minority groups.

Disabled people affirm that the design of the environment often disables them. In better-designed environments, they are disabled less, or not at all. This affirmation arises in part from the understanding that while medical intervention can improve the health issues inherent in certain forms of disability, it does not address societal issues that prevail regardless of the extent or success of medical intervention. In conjunction with this view of changing the environment from a disabling to an enabling atmosphere, advocates of the social model persevere in the de-institutionalization of disabled persons by encouraging maximum integration with non-disabled peers, especially, but not exclusively, in the school environment.

The cultural model of deafness arises from, but is not limited to, deaf people themselves, especially congenitally deaf people whose primary language is the sign language of their nation or community, as well as their children, families, friends and other members of their social networks. Invoked also are people within the social science professions which seek to identify, define and conceptualize the very essence of what constitutes a culture or cultural model of human experience. Also included are professionals in mediating roles between cultures, notably persons engaged in activities of simultaneous interpretation, and schools. This cultural model of deafness represents the natural evolution of the social networks of a minority language group. In this view the conceptualization of deafness is seen from a "community asset" stance. From the conceptual framework of the cultural model come implicit questions, such as: How is deafness influenced by the physical and social environment in which it is embedded; What are the interdependent values, mores, art forms, traditions, organizations, and language that characterize this culture?

Both the medical model and the social model are seen, at the least, to be in conflict with, and at the most, inapplicable to deafness when viewed from the cultural model of deafness.

In contrast to the medical model of Deafness, the deaf community, rather than embrace the view that deafness is a "personal tragedy", sees all aspects of the deaf experience as positive. The birth of a deaf child is seen as a cause for celebration and deaf people are known to travel great distances to see a deaf child.

Deaf people point to the perspective on child rearing they share with hearing people. Both hearing and deaf parents understand that it is easier for a hearing parent to raise a hearing child because of their intimate understanding of the hearing state of being. It follows that a deaf parent will have an easier experiences raising a deaf child since deaf parents have an intimate understanding of the deaf state of being. Evidence of deaf parental success is revealed in scholastic achievement. Deaf children who have deaf parents that communicate in sign language perform better than all other deaf children in academic achievement and acquisition of the majority language regardless of the manner in which the children adapted to deafness. This includes children who adapted using speech and lipreading, prosthetic devices such as the cochlear implant, artificial language systems such as Signing Exact English and Cued Speech, and hearing aid technology.

According to research in the social sciences, membership in the deaf community is a matter of culturally determined behaviors and not of medical diagnosis. Thus membership is not seen as the act of admittance by an insider group or even by anyone at all, but by examining individual behavior to determine how closely it resembles the known culturally determined behaviors found in the community of deaf people. Since sign language stands as the single most valued aspect of deaf culture, it reveals whether an individual belongs to this language minority in the same manner as embracing the Spanish language reveals identity with Hispanic-American culture, another example of a language minority. Groups disadvantaged by majority culture and practices, such as the deaf community, have commonalities with other groups. People with disabilities, gay people, women, and, arguably, African-Americans, are not linguistic minorities, as are members of the deaf community, since their culturally determined behaviors do not center on a unifying language as in the communities of Hispanic-Americans and Native-Americans. Gay culture and American deaf culture, both of which experience the disadvantages of being minority cultures, bear resemblance to one another in that most members of these two minority groups do not share their minority identity with their parents and cannot develop it at home. However, gay culture does not rally around a unifying language as is seen with a minority language group like the community of deaf people.

Members of the deaf communities most certainly do find a parallel with peoples with disabilities, but no more or less than they do with African-Americans, and Hispanic-Americans, all of whom are disadvantaged by the beliefs and practices of the majority culture. However, a line is drawn in deaf culture in the case of disabilities when "respecting that unique organization of life while regretting the conditions that create it" represents a conception of the highest quality of life. It is a conception that is considered inappropriate in deaf culture.

The residential schools for deaf children provide an example for illustration. The residential schools serve as a vital link in the transmission of deaf culture and language and typically provide a rich quality of life. Deaf cultural values find abhorrent occasional proposals to dismantle the residential schools since they are considered the best possible environment, the highest quality of life, in which to acquire and enrich sign language fluency and pass on Deaf cultural values that serve as tools and solutions to challenges in a predominantly hearing world. This view sharply contrasts with the Social Model of Disability, which finds abhorrent segregated schooling of disabled children in special residential schools and prefers the "all-inclusive" environment of neighborhood schools. Research literature shows that no matter whether deaf people use sign language, speech, or assistive technology like the hearing aid and the cochlear implant prosthesis, the majority of deaf adults eventually marry another deaf person and join the deaf community to share in the rewards of the language and culture.

The deaf cultural model points out that these acts also demonstrate an example of respecting and embracing the totality of the deaf experience rather than regretting it. The conflict or inappropriateness of the Social Model rests on this and many other examples in which efforts to promote inclusion at every level produces negative impact on deaf people. Proponents of the social model, understandably, are generally aware of this dilemma and have a great respect for deaf cultural views.

There is a deaf community with its own language and culture, so there is a cultural frame in which to be deaf is not to be infirm or disabled. To the contrary, it is an asset of and for the deaf community to be deaf in behavior, values, knowledge and fluency in sign language. It is within this community bonded by shared culture and language that lives defined by diagnosis, disadvantages imposed by majority beliefs and practices, and disabilities tied to inappropriate models of language and social enrichment, that, according to the cultural model of deafness, deaf people find themselves both enabled and socially advantaged. The experience of a language minority such as the deaf thus seen, amounts to a social disadvantage no more or less troubling than it would be for any language minority. In terms of its effect on mental health, deaf cultural attitudes conclude that a minority language group's disadvantages are preferred to a lifetime of viewing one's self or one's group as infirm or disabled.

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Nonsyndromic deafness

Nonsyndromic deafness is hearing loss that is not associated with other signs and symptoms. In contrast, syndromic deafness involves hearing loss that occurs with abnormalities in other parts of the body.

Genetic changes are related to the following types of nonsyndromic deafness.

The different types of nonsyndromic deafness are named according to their inheritance patterns. Autosomal dominant forms are designated DFNA, autosomal recessive forms are DFNB, and X-linked forms are DFN. Each type is also numbered in the order in which it was described. For example, DFNA1 was the first described autosomal dominant type of nonsyndromic deafness. Mitochondrial nonsyndromic deafness involves changes to the small amount of DNA found in mitochondria, the energy-producing centers within cells.

Most forms of nonsyndromic deafness are associated with permanent hearing loss caused by damage to structures in the inner ear. The inner ear consists of three parts: a snail-shaped structure called the cochlea that helps process sound, nerves that send information from the cochlea to the brain, and structures involved with balance. Loss of hearing caused by changes in the inner ear is called sensorineural deafness. Hearing loss that results from changes in the middle ear is called conductive hearing loss. The middle ear contains three tiny bones that help transfer sound from the eardrum to the inner ear. Some forms of nonsyndromic deafness involve changes in both the inner ear and the middle ear; this combination is called mixed hearing loss.

The severity of hearing loss varies and can change over time. It can affect one ear (unilateral) or both ears (bilateral). Degrees of hearing loss range from mild (difficulty understanding soft speech) to profound (inability to hear even very loud noises). The loss may be stable, or it may progress as a person gets older. Particular types of nonsyndromic deafness often show distinctive patterns of hearing loss. For example, the loss may be more pronounced at high, middle, or low tones.

Nonsyndromic deafness can occur at any age. Hearing loss that is present before a child learns to speak is classified as prelingual or congenital. Hearing loss that occurs after the development of speech is classified as postlingual.

About 1 in 1,000 children in the United States is born with profound deafness. By age 9, about 3 in 1,000 children have hearing loss that affects the activities of daily living. More than half of these cases are caused by genetic factors. Most cases of genetic deafness (70 % to 80 %) are nonsyndromic; the remaining cases are caused by specific genetic syndromes. In adults, the chance of developing hearing loss increases with age; hearing loss affects half of all people older than 80 years.

Mutations in the ACTG1, CDH23, CLDN14, COCH, COL11A2, DFNA5, ESPN, EYA4, GJB2, GJB6, KCNQ4, MYO15A, MYO6, MYO7A, OTOF, PCDH15, POU3F4, SLC26A4, STRC, TECTA, TMC1, TMIE, TMPRSS3, USH1C, and WFS1 genes cause nonsyndromic deafness.

The GJB3 and MYO1A genes are associated with nonsyndromic deafness.

The causes of nonsyndromic deafness can be complex. Researchers have identified more than 30 genes that, when mutated, may cause nonsyndromic deafness; however, some of these genes have not been fully characterized. Many genes related to deafness are involved in the development and function of the inner ear. Gene mutations interfere with critical steps in processing sound, resulting in hearing loss. Different mutations in the same gene can cause different types of hearing loss, and some genes are associated with both syndromic and nonsyndromic deafness. In many families, the gene responsible for hearing loss has not been identified.

Deafness can also result from environmental factors or a combination of genetic and environmental factors. Environmental causes of hearing loss include certain medications, specific infections before or after birth, and exposure to loud noise over an extended period.

Nonsyndromic deafness can have different patterns of inheritance. Between 75 % and 80 % of cases are inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Usually, each parent of an individual with autosomal recessive deafness is a carrier of one copy of the altered gene. These carriers do not have hearing loss.

Another 20 % to 25 % of nonsyndromic deafness cases are autosomal dominant, which means one copy of the altered gene in each cell is sufficient to result in hearing loss. People with autosomal dominant deafness most often inherit an altered copy of the gene from a parent who has hearing loss.

Between 1 % and 2 % of cases show an X-linked pattern of inheritance, which means the mutated gene responsible for the condition is located on the X chromosome. Males with X-linked nonsyndromic deafness tend to develop more severe hearing loss earlier in life than females who inherit a copy of the same gene mutation. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Mitochondrial nonsyndromic deafness, which results from changes to the DNA in mitochondria, occurs in fewer than 1 % of cases in the United States. The altered mitochondrial DNA is passed from a mother to her sons and daughters. This type of deafness is not inherited from fathers.

Late onset progressive deafness is the most common neurological disability of the elderly. Although hearing loss of greater than 25 decibels is present in only 1% of young adults between the ages of 18-24 years of age, this increases to 10% in persons between 55-64 years of age and approximately 50% in octogenarians.

The relative contribution of heredity to age –related hearing impairment is not known, however the majority of inherited late-onset deafness is autosomal dominant and non-syndromic (Van Camp et al., 1997). Over forty genes associated with autosomal dominant non-snydromic hearing loss have been localized and of these fifteen have been cloned.

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Post-lingual deafness

Post-lingual deafness is a deafness 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 prelingual deafness. 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 some cases, the loss is extremely sudden and 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. Hearing aids and cochlear implants may be used to regain a sense of hearing, with different people experiencing differing degrees of success. It is possible that the affected person may need to rely on speech-reading and/or sign language for communication.

In most cases the loss is a long term degradation in hearing loss. Discrediting earlier notions of presbycusis, Rosen demonstrated that long term hearing loss is usually the product of chronic exposure to environmental noise in industrialized countries {Rosen, 1965). The U.S. Environmental Protection Agency has asserted the same sentiment and testified before the U.S. Congress that approximately 34 million Americans are exposed to noise pollution levels (mostly from roadway and aircraft noise) that expose humans to noise health effects including the risk of hearing loss {EPA, 1972).

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, 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.

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 adaptations that make it possible for them to live independently. They may have to adapt to using hearing aids or a cochlear implant, develop speech-reading skills, and/or learn sign language. The affected person may need to use a TTY, interpreter, or relay service to communicate over the telephone. 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.

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