Hereditary hearing loss
Hereditary hearing loss, also known as heriditary hearing impairment, or hereditary anacusis, is a partial or total inability to hear. An affected person may be described as hard of hearing. A deaf person has little to no hearing. Hearing loss may occur in one or both ears. In children hearing problems can affect the ability to learn language and in adults it can cause work related difficulties.
- difficulty using the telephone
- loss of directionality of sound
- difficulty understanding speech, especially women and children
- difficulty in speech discrimination against background noise (cocktail party effect)
- sounds or speech becoming dull, muffled or attenuated
- need for increased volume on television, radio, music and other audio sources
- pain or pressure in the ears
- punctured eardrum
- effusion in the middle ear
- otitis externa, inflammation or infection of the ear canal or eardrum
There may also be accompanying secondary symptoms:
- hyperacusis, heightened sensitivity to certain volumes and frequencies of sound, resulting from "recruitment"
- tinnitus, ringing, buzzing, hissing or other sounds in the ear when no external sound is present
- vertigo and disequilibrium
- tympanophonia, abnormal hearing of one's own voice and respiratory sounds, usually as a result of a patulous eustachian tube
- disturbances of sight, speech or swallowing (indicating possible neuroma)
Hearing loss can be inherited. Around 75–80% of all these cases are inherited by recessive genes, 20–25% are inherited by dominant genes, 1–2% are inherited by X-linked patterns, and fewer than 1% are inherited by mitochondrial inheritance.
When looking at the genetics of deafness, there are 2 different forms, syndromic and nonsyndromic. Syndromic deafness occurs when there are other medical problems aside from deafness in an individual. This accounts for around 30% of deaf individuals who are deaf from a genetic standpoint. Nonsyndromic deafness occurs when there are no other problems associated with an individual other than deafness. From a genetic standpoint, this accounts for the other 70% of cases, and represents the majority of hereditary hearing loss. Syndromic cases occur with diseases such as Usher syndrome, Stickler syndrome, Waardenburg syndrome, Alport's syndrome, and neurofibromatosis type 2. These are diseases that have deafness as one of the symptoms or as a common feature associated with it. The genetics that correspond with these various diseases are very complicated and are difficult to explain scientifically because the cause is unknown. In nonsyndromic cases where deafness is the only ‘symptom’ seen in the individual it is easier to pinpoint the genes responsible.
- Recent gene mapping has identified dozens of nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness. The first gene mapped for non-syndromic deafness, DFNA1, involves a splice site mutation in the formin related homolog diaphanous 1 (DIAPH1). A single base change in a large Costa Rican family was identified as causative in a rare form of low frequency onset progressive hearing loss with autosomal dominant inheritance exhibiting variable age of onset and complete penetrance by age 30. The most common type of congenital hearing loss in developed countries is DFNB1, also known as connexin 26 deafness or GJB2-related deafness.
- The most common dominant syndromic forms of hearing loss include Stickler syndrome and Waardenburg syndrome.
- The most common recessive syndromic forms of hearing loss are Pendred syndrome, large vestibular aqueduct syndrome and Usher syndrome.
- The congenital defect microtia can cause full or partial deafness depending upon the severity of the deformity and whether or not certain parts of the inner or middle ear are affected.
- Mutations in PTPRQ are a cause of autosomal-recessive nonsyndromic hearing loss.
It is estimated that half of cases of hearing loss are preventable. A number of preventative strategies are effective including: immunisation against rubella to prevent congenital rubella syndrome, immunization against H. influenza and S. pneumoniae to reduce cases of otitis media, and avoiding or protecting against excessive noise exposure.
The use of antioxidants is being studied for the prevention of hearing loss.
Education regarding noise exposure increases the use of hearing protectors.
Work place noise regulation
In addition, steps can be taken to avoid the production of excessive noise in the workplace. By purchasing less noisy power tools like those found on the NIOSH Power Tools Database and limiting exposure to ototoxic chemicals, great strides can be made in preventing hearing loss. Companies can also provide personal hearing protector devices tailored to both the worker and type of employment. Some hearing protectors universally block out all noise, and some allow for certain noises to be heard. Workers are more likely to wear hearing protector devices when they are properly fitted.
Better enforcement of laws can decrease levels of noise at work.
The United States Preventive Services Task Force recommends screening for all newborns.
The American Academy of Pediatrics advises that children should have their hearing tested several times throughout their schooling:
- When they enter school
- At ages 6, 8, and 10,
- At least once during middle school
- At least once during high school
There is not enough evidence to determine the utility of screening in adults over 50 years old who do not have any symptoms.
Diagnosis of a hearing loss is usually conducted by a general practitioner medical doctor, otolaryngologist, certified and licensed audiologist, school or industrial audiometrist, or other audiology technician.
A case history (usually a written form, with questionnaire) can provide valuable information about the context of the hearing loss, and indicate what kind of diagnostic procedures to employ. Case history will include such items as:
- major concern
- birth and pregnancy information
- medical history
- development history
- family history
- workplace environment
- home Environment
- otoscopy, visual examination of the outer ear, ear canal, eardrum, and middle ear (through the translucent eardrum) using an optical instrument inserted into the ear canal called an otoscope
- differential testing - the Weber, Rinne, Bing and Schwabach tests are simple manual tests of auditory function conducted with a low frequency (usually 512Hz) tuning fork that can provide a quick indication of type of hearing loss: unilateral/bilateral, conductive, or other.
In case of infection or inflammation, blood or other body fluids may be submitted for laboratory Analysis.
Hearing loss is generally measured by playing generated or recorded sounds, and determining whether the person can hear them. Hearing sensitivity varies according to the frequency of sounds. To take this into account, hearing sensitivity can be measured for a range of frequencies and plotted on an audiogram.
Another method for quantifying hearing loss is a speech-in-noise test. As the name implies, a speech-in-noise test gives an indication of how well one can understand speech in a noisy environment. A person with a hearing loss will often be less able to understand speech, especially in noisy conditions. This is especially true for people who have a sensorineural loss – which is by far the most common type of hearing loss. As such, speech-in-noise tests can provide valuable information about a person's hearing ability, and can be used to detect the presence of a sensorineural hearing loss. A recently developed digit-triple speech-in-noise test may be a more efficient screening test.
Otoacoustic emissions test is an objective hearing test that may be administered to toddlers and children too young to cooperate in a conventional hearing test.
Auditory brainstem response testing is used to test for hearing defects caused not by the ear, but by auditory nerves or portions of the brain involved in auditory processing.
In cases of suspected auditory-related brain tumors or physical trauma, an MRI, CT or other kind of scan may be done.
Treatment depends on the specific cause if known as well as the extent, type and configuration of the hearing loss. Most hearing loss, that resulting from age and noise, is progressive and irreversible, and there are currently no approved or recommended treatments; management is by hearing aid. A few specific kinds of hearing loss are amenable to surgical treatment. In other cases, treatment is addressed to underlying pathologies, but any hearing loss incurred may be permanent.
There are a number of devices that can improve hearing in those who are hearing impaired or deaf or allow people with these conditions to manage better in their lives.
Hearing aids are devices that work to improve the hearing and speech comprehension of those with hearing loss.It works by magnifying the sound vibrations in the ear so that one can understand what is being said around them. The use of this technological device may or may not have an effect on one's sociability. Some people feel as if they cannot live without one because they say it is the only thing that keeps them engaged with the public. Others dislike hearing aids very much because they feel wearing them is embarrassing or weird. Due to their low-esteem, they avoid hearing aid usage altogether and would rather remain quiet and to themselves in a social environment.
Many hearing impaired individuals use assistive devices in their daily lives:
- Individuals can communicate by telephone using telephone typewriters (TTY). Other common names are textphone, minicom and telecommunications device for the deaf (TDD). These devices look like typewriters or word processors and transmit typed text over regular telephone lines. This allows communication through visual messaging. TTYs can transmit messages to individuals who don’t have TTY by using the National Relay service which is an operator that acts as a messenger to each caller. For mobile phones, software apps are available to provide TDD/textphone functionality on some carriers/models to provide 2-way communications.
- There are several new telecommunications relay service technologies including IP Relay and captioned telephone technologies. A deaf or hard of hearing person can communicate over the phone with a hearing person via a human translator. Phone captioning is a service in which a hearing person's speech is captioned by a third party, enabling a hearing impaired person to conduct a conversation with a hearing person over the phone. Wireless, Internet and mobile phone/SMStext messaging are beginning to take over the role of the TDD.
- Real-time text technologies, involving streaming text that is continuously transmitted as it is typed or otherwise composed. This allows conversational use of text. Software programs are now available that automatically generate a closed-captioning of conversations. Examples include discussions in conference rooms, teleconference calls, classroom lectures, and/or religious services.
- Instant messaging software.
- Videophones and similar video technologies can be used for distance communication using sign language. Video conferencing technologies permit signed conversations as well as permitting a sign language–English interpreter to voice and sign conversations between a hearing impaired person and that person's hearing party, negating the use of a TTY device or computer keyboard.
- Video relay service and video remote interpreting (VRI) services also use a third-party telecommunication service to allow a deaf or hard-of-hearing person to communicate quickly and conveniently with a hearing person, through a sign language interpreter.
- Hearing dogs are a specific type of assistance dog specifically selected and trained to assist the deaf and hearing impaired by alerting their handler to important sounds, such as doorbells, smoke alarms, ringing telephones, or alarm clocks.
- 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 reduced the need for deaf and hard-of-hearing people to use a third-party Telecommunications Relay Service to communicate with the hearing and other hearing impaired people.
- A person with hearing loss cannot always hear the phone or distinguish their own ringtone from another. A signalling transmitter can be attached to a phone that will cause a light or a vibration device to activate. Transmitters can also be used to activate visuals cues to represent fire alarms.
- Individuals with hearing loss require phones with amplifiers that have a higher power of amplification when compared to a regular phone. The Hearing Aid Telephone Interconnect System is a hands free amplification system which allows people to amplify sound when using telephones, cell phones, computer and pay phones by way of the attachment of a portable unit
Wireless Hearing aids
A wireless device has two main components: a transmitter and a receiver. The transmitter broadcasts the captured sound, and the receiver detects the broadcast audio and enables the incoming audio stream to be connected to accommodations such as hearing aids or captioning systems.
Three types of wireless systems are commonly used: FM, audio induction loop, and InfraRed. Each system has advantages and benefits for particular uses. FM systems can be battery operated or plugged into an electrical outlet. FM system produce an analog audio signal, meaning they have extremely high fidelity. Many FM systems are very small in size, allowing them to be used in mobile situations. The audio induction loop permits the listener with hearing loss to be free of wearing a receiver provided that the listener has a hearing aid or cochlear implant processor with an accessory called a "telecoil". If the listener does not have a telecoil, then he or she must carry a receiver with an earpiece. As with FM systems, the infrared (IR) system also requires a receiver to be worn or carried by the listener. An advantage of IR wireless systems is that people in adjoining rooms cannot listen in on conversations, making it useful for situations where privacy and confidentiality are required. Another way to achieve confidentiality is to use a hardwired amplifier, which contains or is connected to a microphone and transmits no signal beyond the earpiece plugged directly into it.
There is no treatment surgical or otherwise for hearing lost due to the most common causes (age, noise and genetic defects). For a few specific conditions, surgical intervention can provide a remedy:
- surgical correction of superior canal dehiscence
- myringotomy, surgical insertion of drainage ventilation tubes in the tympanic membrane. Such placement is usually temporary until the underlying pathology (infection or other inflammation) can be resolved.
- radiotherapy or surgical excision of acoustic neuroma, though in most cases, it is unlikely that hearing will be preserved
- Stapedectomy and stapedotomy for otosclerosis - replacement or reshaping of the stapes bone of the middle ear can restore hearing in cases of conductive hearing loss
Surgical and implantable hearing aids are an alternative to conventional external hearing aids. If the ear is dry and not infected, an air conduction aid could be tried; if the ear is draining, a direct bone condition hearing aid is often the best solution. If the conductive part of the hearing loss is more than 30–35 dB, an air conduction device could have problems overcoming this gap. A bone-anchored hearing aid could, in this situation, be a good option. The active bone conduction hearing implant Bonebridge is also an option. This implant is invisible under the intact skin and therefore minimises the risk of skin irritations.
Cochlear implants improve outcomes in people with hearing loss in either one or both ears. They work by artificial stimulation of the cochlear nerve by providing an electric impulse substitution for the firing of hair cells. They are expensive, and require programming along with extensive training for effectiveness.
Cochlear implants as well as bone conduction implants can help with single sided deafness. Middle ear implants or bone conduction implants can help with conductive hearing loss.
People with cochlear implants are at a higher risk for bacterial meningitis. Thus, meningitis vaccination is recommended. People who have hearing loss, especially those who develop a hearing problem in childhood or old age, may need support and technical adaptations as part of the rehabilitation process. Recent research shows variations in efficacy but some studies show that if implanted at a very young age, some profoundly impaired children can acquire effective hearing and speech, particularly if supported by appropriate rehabilitation.
For a classroom setting, children with hearing loss often benefit from interventions. One simple example is providing favorable seating for the child. Having the student sit as close to the teacher as possible improves the student's ability to hear the teacher's voice and to more easily read the teacher's lips. When lecturing, teachers should try to look at the student as much as possible and limit unnecessary noise in the classroom. In particular, the teacher should avoid talking when their back is turned to the classroom, such as while writing on a whiteboard.
Some other approaches for classroom accommodations include pairing hearing impaired students with hearing students. This allows the hearing impaired student to ask the hearing student questions about concepts that they have not understood. The use of CART (Communication Access Real Time) systems, where an individual types a captioning of what the teacher is saying, is also beneficial. The student views this captioning on their computer. Automated captioning systems are also becoming a popular option. In an automated system, software, instead of a person, is used to generate the captioning. Unlike CART systems, automated systems generally do not require an Internet connection and thus they can be used anywhere and anytime. Another advantage of automated systems over CART is that they are much lower in cost. However, automated systems are generally designed to only transcribe what the teacher is saying and to not transcribe what other students say. An automated system works best for situations where just the teacher is speaking, whereas a CART system will be preferred for situations where there is a lot of classroom discussion.
For those students who are completely deaf, one of the most common interventions is having the child communicate with others through an interpreter using sign language