Unilateral hearing loss


Unilateral hearing loss is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.

Signs and symptoms

Patients with unilateral hearing loss have difficulty:
In quiet conditions, speech discrimination is no worse than normal hearing in those with partial deafness; however, in noisy environments speech discrimination is almost always severe.
The prevalence is 3-8.3% of the population. Individuals who are diagnosed with Single Sided Deafness have difficulties with sound localization and speech in noise discrimination. Children with SSD are more likely to experience developmental delays- school, speech, behavioral problems.

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, and mastoiditis.
SSD is most severe form of unilateral hearing loss causes: sudden sensorineural hearing loss, acoustic neuroma, anomalies inner ear abnormalities, cochlear nerve deficiency, mumps, congenital cytomegalovirus infection, meningitis and auditory neuropathy spectrum disorder treatment is based on the cause of the hearing loss. Limited treatment when the cause is the Central auditory system or Auditory nerve.

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.

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. There is also a surgical option and that is a cochlear implant which is 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. People with profound unilateral hearing loss can only hear in monaural.
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 hear only about 30–35% of the conversation. A person with SSD needs to make more effort when communicating with others. 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.
SSD also negatively affects hearing and comprehension by making it impossible for the patient to determine the direction, distance and movement of sound sources. In an evaluation using the Speech, Spatial and Qualities of Hearing Scale questionnaire, SSD results in a greater handicap than subjects with a hearing loss in both ears.
Profound SSD is often confused with sensory discrimination disorder, 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:
Adaptation in the central nervous system through "neural-plasticity" or biological maturation over time does not improve the performance of monaural listening. 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 hearing ability.
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.

Evaluation

As of 2012 there has only been one small-scale study comparing CROS systems.
One study of the BAHA system showed a benefit depending on the patient's transcranial attenuation. Another study showed that sound localisation was not improved, but the effect of the head shadow was reduced.

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.
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 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, 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.