Deafblindness: living with sensory deprivation

Abstract

Claes Moller is a professor at the Department of Audiology, Sahlgrenska University Hospital, Gothenburg, Sweden I went to the doctor and he told me that I will go deaf and blind. He doesn't know when, but it might be in the near future. Then the doctor abruply left the room. No! Not my hearing, not my vision! It is not fair! How could God do this to me? Why wasn't Itold until Iwas grown up? Ihave had vision and hearing problems for as long as Ican remember and no one told me. This is not fair. Somebody help me!” Deafblindness is a heterogeneous hearing and vision disorder, which can be caused by trauma, diseases, or inherited syndromes. Communication, from the Latin word “communicare”, means to do things together. Thus, to be fast and reliable, communication between human beings relies on vision and hearing. These two senses are complementary and enhance each other. In a noisy environment when it is difficult to hear, visual cues such as body language and expressions can supplement our understanding. Likewise, when vision is poor, hearing has a major role in the localisation of sounds and the detection of danger. A deafblind person can be profoundly deaf and completely blind, completely deaf with visual impairment, completely blind with hearing problems, or have hearing and vision dysfunction. Since vision and hearing interact, deafblindness means that in this instance, one plus one equals three. Although the division is artificial, deafblindness is best understood when discussed as either congenital or acquired deafblindness. Congenital deafblindness (blindness and profound deafness) is extremely rare; about one in 10 000 newborn babies is affected. Causes of congenital deafblindness include genetic problems, premature birth, and infections. Children with congenital deafblindness very often have other problems such as mental retardation or cerebral palsy. At least 20 different genetic syndromes are known to be associated with the disorder—genes and mutations have been identified for some. Because of the rareness of these genetic conditions and difficulties in assessment, congenital deafblindness can sometimes be missed and attributed to other conditions. The hallmark of congenital deafblindness is extreme difficulty in communication. Communication training is lifelong and relies heavily on tactile sign language and input via the remaining senses. In congenital deafblindness the goal so far has been to open up a new channel for communication or hearing and very promising achievements have been made—especially with the advent of cochlear implants. If a deafblind child does not have brain damage, early cochlear implantation can result in hearing and speech. However, in other syndromes associated with brain damage, the goal is simply to create an awareness and basic recognition of sounds. People with acquired deafblindness are those who have not been completely deafblind since birth. There are many causes of acquired deafblindness, which affects many more people than does the congenital disability. Usually, only young and middle-age people are included in the count of people with acquired deafblindness. However, many very old people can have a severe hearing loss as well as a severe visual impairment caused by conditions such as cataracts or macula degeneration. There are about 50 hereditary syndromes that cause acquired deafblindness. Most of them are rare and some also affect other organs. The most common is Usher syndrome, which accounts for almost half of all people with acquired deafblindness. Usher syndrome is an autosomal recessive disorder and in most countries, the prevalence is 8–10 per 100 000 newborn babies. Usher syndrome is clinically divided into three main types, with several genes implicated in different types of the syndrome. In type 1, seven different genes have been localised. One of the most common types is Usher type 1b, which has mutations in a gene called myosin VIIA. This gene is expressed in the hair cells of the cochlea and in retinal photoreceptors. In Usher type 2, mutations are found in usherin (type 2a). This gene is also expressed in the cochlea and in the retina but it seems to cause disturbances in supporting cells instead of the hair cells. Collaboration between researchers in Gothenburg, Sweden, and Omaha, USA, has yielded many new insights to Usher syndrome, and has resulted in advances that will allow early and accurate diagnosis. Hopefully, in the very near future, improved understanding and treatments will be available not only for Usher syndrome, but also for other hearing loss disorders. Other syndromes that cause deafblindness in varying degrees include Alström's syndrome, CHARGE association, Alport's syndrome, as well as many other rare syndromes. Recently, many have been clinically characterised and genetically localised. The aim of all treatments of deafblind people is to reduce their isolation. Cochlear implants have been widely used in people with congenital and acquired profound deafness since the 1980s, and are the most promising and revolutionary technical aid so far in helping deafblind people to hear. A cochlear implant is an electrode implanted in the cochlea that transform sounds into electrical impulses, which are transmitted to auditory nerve endings. The stimulus is then propagated to the brain's hearing centres. The cochlea is arranged phonotopically, much like a piano. The primary centre for high-pitch tones is at the beginning of the cochlea, and low-pitch tones are registered at the base of the structure. Since in most cases the cause of deafness is non-functioning haircells, the electrode can, by strong electrical impulses, reach this damaged region and generate an electrical impulse in the auditory nerve endings. So far, about 40 000 deaf and deafblind people have benefited from cochlear implants; if implanted early enough (before age 3 years) most children will acquire hearing and speech. There has been some scepticisim about and resistance towards cochlear implants within the deaf community. A fear exists that the implants are a threat to deaf culture. However, in the past year, some deaf children of deaf parents have had implants. Visual implants have not yet been developed, but early work with implantation of cameras and electrodes in the retina has shown promising results. New knowledge in other fields can reduce the effects of impairment associated with deafblindness. Computers and the internet, for example, have substantially reduced the isolation of people with deafblindness. Software developments have also enhanced communication through Braille, speech synthesisers, and Magnivision. The internet has opened up communication with other deafblind people and the rest of the community. Many networks exist, both within the European community and in other parts of the world that connect deafblind people. Identification of the precise mutation of genetic disorders might, in the future, lead to precise medical and genetic treatment. In addition, progressive loss of hearing and vision might be preventable with drugs such as antioxidants (eg, vitamin A, E, or C) or growth hormones. Another possibility is stem-cell treatment. Research in regeneration of nerve cells within the inner ear and the retina continues. The new insights in genetics, combined with more advanced diagnostic tools for assessment of vision and hearing, make early and correct diagnosis possible. These advances are important for patients, since an early diagnosis will immediately improve the possibility of giving an accurate prognosis. Informing a patient about their outlook will reduce fear and misunderstanding, foster more realistic expectations, and allow better rehabilitation and, hopefully in the future, treatment.