| Unilateral hearing loss | |
|---|---|
| Classification and external resources | |
| ICD-10 | H90.1, H90.4, H90.7 |
Unilateral hearing loss (UHL) or single-sided deafness (SSD) is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.
Contents |
Patients with unilateral hearing loss have difficulty in
In quiet conditions, speech discrimination is approximately the same for normal hearing and those with unilateral deafness;[1] however, in noisy environments speech discrimination varies individually and ranges from mild to severe.[1][2]
Known causes include physical trauma, acoustic neuroma, measles, Labyrinthitis, microtia, meningitis, Ménière's disease, or mumps (Epidemic parotitis).
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.[3]
Profound unilateral hearing loss is a specific type of hearing impairment when one ear has no functional hearing ability (91dB 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 in background noise difficult. With speech and background noise presented at the same level, persons with unilateral deafness were found to hear only about 30-35% of the conversation.[4] A person with SSD needs to make more effort when communicating with others.[5] When a patient is able to 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.[6]
SSD also negatively affects hearing by making it more difficult for the patient to determine the direction, distance and movement of sound sources.[6] In an evaluation using the Speech, Spatial and Qualities of Hearing Scale (SSQ) questionnaire9, SSD patients actually perceived a greater handicap than subjects with a hearing loss in both ears.
SSD is known to cause:
Learning of the central nervous system by "plasticity" or biological maturation over time does not improve the performance of monaural listening.[2]
Contralateral Routing of Signals (CROS) hearing aid: a hearing aid that takes sound from the ear with poorer hearing and transmits to the ear with better hearing. This kind of hearing aid can involve two behind-the-ear units connected either by wire or by wireless transmission. There are also systems incorporated into eyeglasses. Bone Conduction Hearing Aid (Baha): transfers sound through bone conduction and stimulates the cochlea of the normal hearing ear. One study of the system showed a benefit depending on the patient's transcranial attenuation.[7] Another study showed that sound localisation was not improved, but the effect of the head shadow was reduced.[8]
When wearing stereo headphones, people with unilateral hearing loss can hear only one channel, hence only half of the components of the music, e.g., bass or piano, but not both (although most modern recordings feature amplitude difference in instruments between the channels, rather than complete silence in one channel and full volume on the other, with respect to one specific instrument). The need for headsets for cellphones and VOIP communication has made monaural headphones, which often combine stereo to mono sound, readily available to solve the problem. Stereo headphones may also be connected to a sound source with a stereo-to-monaural adapter to achieve a similar effect (the two stereo channels going into one headphone).
Some portable music players, such as the iPhone from Apple, have accessibility features which will allow you to change the sound to mono.[9]
Mild and Unilateral Hearing Loss: Implications for Early Intervention
|
|||||||||||||||||||||||||||||||||||||||