Unilateral hearing loss | |
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Other names | Single-sided deafness (SSD) |
Specialty | Audiology, ear, nose, and throat |
Unilateral hearing loss (UHL) is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.
Patients with unilateral hearing loss have difficulty:
In quiet conditions, speech discrimination is no worse than normal hearing in those with partial deafness; [1] however, in noisy environments speech discrimination is almost always severe. [1] [2]
The prevalence is 3–8.3% of the population. [3] Individuals who are diagnosed with Single Sided Deafness have difficulties with sound localization and speech in noise discrimination. [3] Children with SSD are more likely to experience developmental delays- school, speech, behavioral problems. [3]
Known causes include genetics, maternal illness and injury. Examples of these causes are physical trauma, acoustic neuroma, maternal prenatal illness such as measles, labyrinthitis, microtia, meningitis, Ménière's disease, Waardenburg syndrome, mumps (epidemic parotitis),mastoiditis or due to an overstrained nervus vestibulocochlearis after a brain surgery to close to the nerve.
SSD's most severe form of unilateral hearing loss is caused by: sudden sensorineural hearing loss (SSNHL), acoustic neuroma, anomalies inner ear abnormalities, cochlear nerve deficiency (CND), mumps, congenital cytomegalovirus (CMV) infection, meningitis and auditory neuropathy spectrum disorder (ANSD) treatment is based on the cause of the hearing loss. Limited treatment when the cause is the Central auditory system or Auditory nerve. [4]
A 1998 study of schoolchildren found that per thousand, 6–12 had some form of unilateral hearing loss and 0–5 had moderate to profound unilateral hearing loss. It was estimated that in 1998 some 391,000 school-aged children in the United States had unilateral hearing loss. [5]
Profound unilateral hearing loss is a specific type of hearing loss when one ear has no functional hearing ability (91 dB or greater hearing loss). People with profound unilateral hearing loss can only hear in monaural (mono).
Profound unilateral hearing loss or single-sided deafness, SSD, makes hearing comprehension very difficult. With speech and background noise presented at the same level, persons with unilateral deafness were found to listen only about 30–35% of the conversation. [6] A person with SSD needs to make more effort when communicating with others. [7] When a patient can hear from only one ear, and there are limited possibilities to compensate for the disability, e.g., changing listening position, group discussions and dynamic listening situations become difficult. Individuals with profound unilateral hearing loss are often perceived as socially awkward due to constant attempts to maximize hearing leading to socially unique body language and mannerisms. [8]
UHL also negatively affects hearing and comprehension by making it impossible for the patient to determine the direction, distance and movement of sound sources. [8] In an evaluation using the Speech, Spatial and Qualities of Hearing Scale (SSQ) questionnaire, SSD results in a greater handicap than subjects with a severe hearing loss in both ears.
Profound SSD is often confused with sensory discrimination disorder (SDD), a type of sensory processing disorder, and can lead to incorrect processing of sensory information or auditory input during interpersonal communications.
Profound unilateral hearing loss is known to cause:
Several hearing devices have been shown to benefit individuals with unilateral hearing loss.
Contralateral Routing of Signals (CROS) hearing aids are hearing aids that take sound from the ear with poorer hearing and transmit to the ear with better hearing. They consist of a microphone placed near the impaired ear and an amplifier (hearing aid) near the normal ear. The two units are connected either by a wire behind the neck or by wireless transmission. The aid appears as two behind-the-ear hearing aids and is sometimes incorporated into eyeglasses. [9]
Bone Anchored Hearing Aids (BAHAs) are bone conduction devices that are surgically implanted into the mastoid bone, with an abutment protruding through the skin. The external hearing aid clicks onto the abutment and uses bone conduction to transmit sound to the cochlea of the normal hearing ear. The external component can also be attached to a headband or softband and used as a non-surgical device. [10]
The BONEBRIDGE bone conduction implant is surgically implanted into the mastoid bone completely underneath the skin. The audio processor is worn externally and held in place by magnets. It sends sound as electrical signals through the skin to the implant. The implant then sends sound vibrations to the cochlea of the normal hearing ear through the skull via bone conduction. [11]
The ADHEAR bone conduction system is a non-surgical device that sticks to the skin behind the ear. It vibrates to send sound vibrations through the skin and the skull bone to the cochlea of the normal hearing ear. [12]
The SoundBite intraoral bone conduction system used bone conduction via the teeth. One component resembled a conventional behind-the-ear hearing aid that wirelessly connects to a second component worn in the mouth that resembles a conventional dental appliance. The device was discontinued in 2015 and is no longer available. [13]
A cochlear implant can also be used to treat unilateral hearing loss in many countries. The device is surgically implanted in the cochlea of non-hearing ear, with a sound processor worn externally. Using electrical stimulation of the cochlea, sound is sent to the hearing nerve and onto the brain. [14]
According to Snapp 2019, CROS technology solutions provide a noninvasive, aesthetically appealing, low-cost option for individuals with single sided deafness (SSD). The primary benefits of a CROS hearing devices are improved sound awareness from the impaired side and better hearing in noise when speech is located on the impaired side. However, CROS solutions do not provide restoration of binaural hearing and cannot improve tasks requiring binaural input, such as localization. [15]
One study of the BAHA system showed a benefit depending on the patient's transcranial attenuation. [16] Another study showed that sound localization was not improved, but the effect of the head shadow was reduced. The BAHA system has been shown to have higher patient satisfaction and greater perceived benefit by users than the CROS system. [17]
The BONEBRIDGE system has been shown to provide good hearing outcomes, and patients also reported high subjective benefit. [18] The device has been shown to decrease the head shadow effect. [19] Sprinzl et al. (2016) also found that the BONEBRIDGE system had a lower complication rate when compared to other implanted bone conduction devices. [20]
Studies of the ADHEAR system have shown that patients report higher comfort satisfaction and longer daily wearing times compared to the BAHA system with a headband or softband, due to the lack of pressure on the skin. [21] Better outcomes compared to CROS hearing aids have also been reported. [22]
Studies on the SoundBite system showed it to have strong hearing benefit and high patient satisfaction, particularly due to its non-surgical design. Some users reported acoustic feedback from the device. [23]
Cochlear implants (CIs) have been shown to benefit patients with unilateral hearing loss in terms of tinnitus reduction, localization, speech understanding, and quality of life (QoL). [24] The increased ability to locate sounds is explained by the fact that, unlike with the other treatments available, treating unilateral hearing loss with a cochlear implant results in both cochleae being stimulated, which helps the brain to better decipher the location of the sound. However, patients may still have difficulties at frontal locations and on the CI side. [25]
School-age children with unilateral hearing loss tend to have poorer grades and require educational assistance. This is not the case with everyone, however. They can also be perceived to have behavioral issues. [26]
People affected by UHL have great difficulty locating the source of any sound. They may be unable to locate an alarm or a ringing telephone. The swimming game Marco Polo is generally impossible for them.
When wearing stereo headphones, people with unilateral hearing loss can hear only one channel, hence the panning information (volume and time differences between channels) is lost; some instruments may be heard better than others if they are mixed predominantly to one channel, and in extreme cases of sound production, such as complete stereo separation or stereo-switching, only part of the composition can be heard; in games using 3D audio effects, sound may not be perceived appropriately due to coming to the disabled ear. This can be corrected by using settings in the software or hardware—audio player, OS, amplifier or sound source—to adjust balance to one channel (only if the setting downmixes sound from both channels to one), or there may be an option to outright downmix both channels to mono. Such settings may be available via the device or software's accessibility features. [27] [28]
Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in loneliness.
A cochlear implant (CI) is a surgically implanted neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception. With the help of therapy, cochlear implants may allow for improved speech understanding in both quiet and noisy environments. A CI bypasses acoustic hearing by direct electrical stimulation of the auditory nerve. Through everyday listening and auditory training, cochlear implants allow both children and adults to learn to interpret those signals as speech and sound.
A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as personal sound amplification products (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".
Bone conduction is the conduction of sound to the inner ear primarily through the bones of the skull, allowing the hearer to perceive audio content even if the ear canal is blocked. Bone conduction transmission occurs constantly as sound waves vibrate bone, specifically the bones in the skull, although it is hard for the average individual to distinguish sound being conveyed through the bone as opposed to the sound being conveyed through the air via the ear canal. Intentional transmission of sound through bone can be used with individuals with normal hearing — as with bone-conduction headphones — or as a treatment option for certain types of hearing impairment. Bones are generally more effective at transmitting lower-frequency sounds compared to higher-frequency sounds.
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear, sensory organ, or the vestibulocochlear nerve. SNHL accounts for about 90% of reported hearing loss. SNHL is usually permanent and can be mild, moderate, severe, profound, or total. Various other descriptors can be used depending on the shape of the audiogram, such as high frequency, low frequency, U-shaped, notched, peaked, or flat.
The Weber test is a screening test for hearing performed with a tuning fork. It can detect unilateral (one-sided) conductive hearing loss and unilateral sensorineural hearing loss. The test is named after Ernst Heinrich Weber (1795–1878). Conductive hearing ability is mediated by the middle ear composed of the ossicles: the malleus, the incus, and the stapes. Sensorineural hearing ability is mediated by the inner ear composed of the cochlea with its internal basilar membrane and attached cochlear nerve. The outer ear consisting of the pinna, ear canal, and ear drum or tympanic membrane transmits sounds to the middle ear but does not contribute to the conduction or sensorineural hearing ability save for hearing transmissions limited by cerumen impaction.
Auditory neuropathy (AN) is a hearing disorder in which the outer hair cells of the cochlea are present and functional, but sound information is not transmitted sufficiently by the auditory nerve to the brain. Hearing loss with AN can range from normal hearing sensitivity to profound hearing loss.
Presbycusis, or age-related hearing loss, is the cumulative effect of aging on hearing. It is a progressive and irreversible bilateral symmetrical age-related sensorineural hearing loss resulting from degeneration of the cochlea or associated structures of the inner ear or auditory nerves. The hearing loss is most marked at higher frequencies. Hearing loss that accumulates with age but is caused by factors other than normal aging is not presbycusis, although differentiating the individual effects of distinct causes of hearing loss can be difficult.
Microtia is a congenital deformity where the auricle is underdeveloped. A completely undeveloped pinna is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Microtia can be unilateral or bilateral. Microtia occurs in 1 out of about 8,000–10,000 births. In unilateral microtia, the right ear is most commonly affected. It may occur as a complication of taking Accutane (isotretinoin) during pregnancy.
A bone-anchored hearing aid (BAHA) is a type of hearing aid based on bone conduction. It is primarily suited for people who have conductive hearing losses, unilateral hearing loss, single-sided deafness and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids. They are more expensive than conventional hearing aids, and their placement involves invasive surgery which carries a risk of complications, although when complications do occur, they are usually minor.
The House Institute Foundation (HIF), formerly the House Ear Institute, is a non-profit 501(c)(3) organization, based in Los Angeles, California, and dedicated to advancing hearing science through research, education, and global hearing health to improve quality of life.
Cochlear is a medical device company that designs, manufactures, and supplies the Nucleus cochlear implant, the Hybrid electro-acoustic implant and the Baha bone conduction implant.
A contralateral routing of signals (CROS) hearing aid is a type of hearing aid that is used to treat a condition in which the patient has no usable hearing in one ear and minimal hearing loss or normal hearing in the other ear. This is referred to as single sided deafness.
Electric acoustic stimulation (EAS) is the use of a hearing aid and a cochlear implant technology together in the same ear. EAS is intended for people with high-frequency hearing loss, who can hear low-pitched sounds but not high-pitched ones. The hearing aid acoustically amplifies low-frequency sounds, while the cochlear implant electrically stimulates the middle- and high-frequency sounds. The inner ear then processes the acoustic and electric stimuli simultaneously, to give the patient the perception of sound.
An auditory brainstem implant (ABI) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf, due to retrocochlear hearing impairment. In Europe, ABIs have been used in children and adults, and in patients with neurofibromatosis type II.
SoundBite Hearing System is a non-surgical bone conduction prosthetic device that transmits sound via the teeth. It is an alternative to surgical bone conduction prosthetic devices, which require surgical implantation into the skull to conduct sound.
A direct acoustic cochlear implant - also DACI - is an acoustic implant which converts sound in mechanical vibrations that stimulate directly the perilymph inside the cochlea. The hearing function of the external and middle ear is being taken over by a little motor of a cochlear implant, directly stimulating the cochlea. With a DACI, people with no or almost no residual hearing but with a still functioning inner ear, can again perceive speech, sounds and music. DACI is an official product category, as indicated by the nomenclature of GMDN.
MED-EL is a global medical technology company specializing in hearing implants and devices. They develop and manufacture products including cochlear implants, middle ear implants and bone conduction systems.
Identification of a hearing loss is usually conducted by a general practitioner medical doctor, otolaryngologist, certified and licensed audiologist, school or industrial audiometrist, or other audiometric technician. Diagnosis of the cause of a hearing loss is carried out by a specialist physician or otorhinolaryngologist.
A middle ear implant is a hearing device that is surgically implanted into the middle ear. They help people with conductive, sensorineural or mixed hearing loss to hear.
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