Unilateral hearing loss

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.

Unilateral hearing loss
Other namesSingle-sided deafness (SSD)
SpecialtyAudiology, ear, nose, and throat

Signs and symptoms

Patients with unilateral hearing loss have difficulty:

  • Hearing conversation on their impaired side
  • Localizing sound
  • Understanding speech in the presence of background noise
  • In interpersonal interaction in social settings
  • Focusing on individual sound sources in large, open environments
  • Heavy impairment of the auditory Figure–ground perception

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]

Causes

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), and mastoiditis.

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]

Prevalence

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]

Treatment

There are multiple treatments for hearing loss which include either surgical or non-surgical options. Deciding one or the other comes down to whether there is little or no hearing in the affected ear. If there is some hearing in the affected ear then an amplified hearing device may be suggested and it is a non-surgical option. If there is no hearing a special type of hearing aid called a CROS hearing aid is often used as a non-surgical option. There are also surgical options for a cochlear implant, or a bone conduction device. It ultimately comes down to the severity of the hearing loss and which route is best for the patient.

Profound unilateral hearing loss

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 handicap, 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]

SSD 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.

SSD is known to cause:

  • Irritability
  • Sound aversion: any presence of noise, no matter how low
  • Body language and mannerisms which appear socially awkward or unusual, like staring at others mouths or tilt the head frequently
  • Frequent headaches, stress
  • Social isolation
  • Chronic interpersonal communication difficulties due to inability of brain to isolate or beam form sounds and voices of other individuals
  • Appearance of anxiousness even in low noise situations
  • Jumpiness
  • Trouble figuring out where sounds are coming from.
  • Variable light dizziness
  • Trouble paying attention to what people are saying: "evasive" behaviour.
  • Misdiagnoses as ADHD
  • Seeming lack of awareness of other people's personal space and moods since brain is hyper-focused on deciphering auditory information in lieu of non-verbal social cues.
  • Lack of sound depth: any background noise (in the room, in the car) is flat and wrongly interpreted by the brain. The effect is similar to what happens when trying to hear someone speaking in a noisy crowd on a mono TV. The effect is also similar to talking on the phone to someone who is in a noisy environment (see also: King-Kopetzky syndrome)
  • Inability to filter out background noise or selectively listen to only the important portion of the noise in the environment.
  • For sensorineural hearing loss, the lack of input coming from the damaged sensory apparatus can cause "ghost beeps" or ringing/tinnitus as the brain attempts to interpret the now missing sensory data. The frequency and the volume of the noise can increase according to one's physical condition (stress, fatigue, etc.). This can aggravate social problems and increase the difficulty of speech comprehension.
  • Talking loudly or "broadcasting": the affected person cannot perceive the volume of his or her voice relative to other people in the same room or close company, resulting in being characterized by others (who may be located beyond normal auditory range) as domineering or boorish

Management

Adaptation in the central nervous system through "neural-plasticity" or biological maturation over time does not improve the performance of monaural listening.[2] In addition to conventional methods for improving the performance of the impaired ear, there are also hearing aids adapted to unilateral hearing loss which are of very limited effectiveness due to the fact that they don't restore the binaural hearing ability, and tend to overload the working ear.

  • 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. There are several types of CROS hearing aid:[9]
    • conventional CROS comprises 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.
    • CIC transcranial CROS comprises a bone conduction hearing aid completely in the ear canal (CIC). A high-power conventional air conduction hearing aid fits deeply into the patient’s deaf ear. Vibration of the bony walls of the ear canal and middle ear stimulates the normal ear by means of bone conduction through the skull.
    • BAHA transcranial CROS Bone Anchored Hearing Aid (BAHA): a surgically implanted abutment transmits sound from the deaf ear by direct bone conduction and stimulates the cochlea of the normal hearing ear.
    • SoundBite Intraoral bone conduction which uses bone conduction via the teeth. One component resembles a conventional behind-the-ear hearing aid that wirelessly connects to a second component worn in the mouth that resembles a conventional dental appliance.[10]

In Germany and Canada, cochlear implants have been used to mostly restore the stereo hearing ability, minimizing the impacts of the SSD and increasing the quality of life of the patient.[11]

Evaluation

As of 2012 there has only been one small-scale study comparing CROS systems.[9]

One study of the BAHA system showed a benefit depending on the patient's transcranial attenuation.[12] Another study showed that sound localisation was not improved, but the effect of the head shadow was reduced.[13]

Other Hearing issues

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.[14]

People afflicted with 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.[15][16]

See also

References
  1. Sargent EW, Herrmann B, Hollenbeak CS, Bankaitis AE (July 2001). "The minimum speech test battery in profound unilateral hearing loss". Otol. Neurotol. 22 (4): 480–6. doi:10.1097/00129492-200107000-00012. PMID 11449104. S2CID 37980161.
  2. Welsh LW, Welsh JJ, Rosen LF, Dragonette JE (December 2004). "Functional impairments due to unilateral deafness". Ann. Otol. Rhinol. Laryngol. 113 (12): 987–93. doi:10.1177/000348940411301209. PMID 15633902. S2CID 3218109.
  3. Sharma, Anu; Glick, Hannah; Campbell, Julia; Torres, Jennifer; Dorman, Michael; Zeitler, Daniel M. (2016). "Cortical Plasticity and Re-organization in Pediatric Single-Sided Deafness Pre- and Post- Cochlear Implantation: A Case Study". Otology & Neurotology. 37 (2): e26–e34. doi:10.1097/MAO.0000000000000904. PMC 6530986. PMID 26756152.
  4. Usami, Shin-ichi; Kitoh, Ryosuke; Moteki, Hideaki; Nishio, Shin-ya; Kitano, Tomohiro; Kobayashi, Masafumi; Shinagawa, Jun; Yokota, Yoh; Sugiyama, Kenjiro; Watanabe, Kizuki (April 2017). "Etiology of single-sided deafness and asymmetrical hearing loss". Acta Oto-Laryngologica. 137 (sup565): S2–S7. doi:10.1080/00016489.2017.1300321. PMID 28366032.
  5. Lee DJ, Gómez-Marín O, Lee HM (August 1998). "Prevalence of unilateral hearing loss in children: the National Health and Nutrition Examination Survey II and the Hispanic Health and Nutrition Examination Survey". Ear Hear. 19 (4): 329–32. doi:10.1097/00003446-199808000-00008. PMID 9728728. S2CID 9790680.CS1 maint: multiple names: authors list (link)
  6. Christensen L, Richter GT, Dornhoffer JL (Feb 2010). "Update on bone-anchored hearing aids in pediatric patients with profound unilateral sensorineural hearing loss". Archives of Otolaryngology–Head & Neck Surgery. 136 (2): 175–7. doi:10.1001/archoto.2009.203. PMID 20157065.
  7. Bess FH, Tharpe AM (February 1986). "An introduction to unilateral sensorineural hearing loss in children". Ear Hear. 7 (1): 3–13. doi:10.1097/00003446-198602000-00003. PMID 3512353. S2CID 46695863.
  8. Noble W, Gatehouse S (2004). "Interaural asymmetry of hearing loss, Speech, Spatial and Qualities of Hearing Scale (SSQ) disabilities, and handicap". International Journal of Audiology. 43 (2): 100–14. doi:10.1080/14992020400050015. PMID 15035562. S2CID 11541363.
  9. Hol, M. K. S.; Kunst, S. J. W.; Snik, A. F. M.; Cremers, C. W. R. J. (2009). "Pilot study on the effectiveness of the conventional CROS, the transcranial CROS and the BAHA transcranial CROS in adults with unilateral inner ear deafness". European Archives of Oto-Rhino-Laryngology. 267 (6): 889–896. doi:10.1007/s00405-009-1147-9. PMC 2857795. PMID 19904546.
  10. Popelka, G. (2010). "SoundBite Hearing System by Sonitus Medical: A New Approach to Single-Sided Deafness". Seminars in Hearing. 31 (4): 393–409. doi:10.1055/s-0030-1268037.
  11. Jacob, R; Stelzig, Y; Nopp, P; Schleich, P (2011). "Audiological results with cochlear implants for single-sided deafness". Hno. 59 (5): 453–460. doi:10.1007/s00106-011-2321-0. PMID 21533601.
  12. Stenfelt S (March 2005). "Bilateral fitting of BAHAs and BAHA fitted in unilateral deaf persons: acoustical aspects". Int J Audiol. 44 (3): 178–89. doi:10.1080/14992020500031561. PMID 15916119. S2CID 37349704.
  13. Hol MK, Bosman AJ, Snik AF, Mylanus EA, Cremers CW (September 2005). "Bone-anchored hearing aids in unilateral inner ear deafness: an evaluation of audiometric and patient outcome measurements". Otol. Neurotol. 26 (5): 999–1006. doi:10.1097/01.mao.0000185065.04834.95. PMID 16151349. S2CID 27082293.
  14. Lieu, J. E. C. (2004). "Speech-Language and Educational Consequences of Unilateral Hearing Loss in Children". Archives of Otolaryngology–Head & Neck Surgery. 130 (5): 524–530. doi:10.1001/archotol.130.5.524. PMID 15148171.
  15. OS X Mavericks: Audio pane of Accessibility preferences
  16. Apple - Accessibility - iOS
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