Unilateral hearing loss
Encyclopedia
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.
In quiet conditions, speech discrimination is approximately the same for normal hearing and those with unilateral deafness; however, in noisy environments speech discrimination varies individually and ranges from mild to severe.
, measles, Labyrinthitis, microtia
, meningitis
, Ménière's disease
, or mumps
(Epidemic parotitis).
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. A person with SSD needs to make more effort when
communicating with others. 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.
SSD also negatively affects hearing by making it more difficult 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 (SSQ) questionnaire9, SSD patients actually perceived a greater handicap than subjects with a hearing loss in both ears.
SSD is known to cause:
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. Another study showed that sound localisation was not improved, but the effect of the head shadow was reduced.
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.
Hearing impairment
-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
where there is normal hearing in one ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
and impaired hearing in the other ear.
Signs and symptoms
Patients with unilateral hearing loss have difficulty in- hearing conversation on their impaired side
- localizing sound
- understanding speech in the presence of background noise.
In quiet conditions, speech discrimination is approximately the same for normal hearing and those with unilateral deafness; however, in noisy environments speech discrimination varies individually and ranges from mild to severe.
Causes
Known causes include physical trauma, acoustic neuromaAcoustic neuroma
A vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve . The term "vestibular schwannoma" involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are...
, measles, Labyrinthitis, microtia
Microtia
Microtia, also called microtia-anotia, is a congenital deformity where the pinna is very small and underdeveloped or absent . It can be unilateral or bilateral . It occurs in 1 out of about 8,000–10,000 births. In unilateral microtia, the right ear is most commonly affected...
, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, Ménière's disease
Ménière's disease
Ménière's disease is a disorder of the inner ear that can affect hearing and balance to a varying degree. It is characterized by episodes of vertigo and tinnitus and progressive hearing loss, usually in one ear. It is named after the French physician Prosper Ménière, who, in an article published...
, or mumps
Mumps
Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...
(Epidemic parotitis).
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.Profound unilateral hearing loss
Profound unilateral hearing loss is a specific type of hearing impairmentHearing impairment
-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
when one ear has no functional hearing ability (91dB or greater hearing loss). People with profound unilateral hearing loss can only hear in monaural
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
(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. A person with SSD needs to make more effort when
communicating with others. 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.
SSD also negatively affects hearing by making it more difficult 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 (SSQ) questionnaire9, SSD patients actually perceived a greater handicap than subjects with a hearing loss in both ears.
SSD is known to cause:
- Irritability
- Frequent headaches, stressStress (medicine)Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
- Social isolation
- 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.
- Mis-diagnoses as ADHD
- Lack of awareness of other peoples personal space and moods
- 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 monoMonauralMonaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
TV. The effect is also similar to talking on the phone to someone who is in a noisy environment (see also: King-Kopetzky syndromeKing-Kopetzky syndromeKing–Kopetzky syndrome is an auditory disability which appears as clinically as a “normal” hearing threshold.It is also known as auditory processing disorder or auditory disability with normal hearing ,...
) - Inability to filter out background noise or selectively listen to only the important portion of the noise in the environment.
- For sensorineural hearing lossSensorineural hearing lossSensorineural hearing loss is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve , the inner ear, or central processing centers of the brain....
, the lack of input coming from the damaged sensory apparatus can cause "ghost beeps" or ringing/tinnitusTinnitusTinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
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.
Management
Learning of the central nervous system by "plasticity" or biological maturation over time does not improve the performance of monaural listening.Contralateral Routing of Signals (CROS) hearing aid
CROS hearing aid
A contralateral routing of signals hearing aid is a type of hearing aid that is used to treat unilateral hearing loss. It takes sound from the ear with poorer hearing and transmits to the ear with better hearing....
: 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)
Bone Anchored Hearing Aid
A Bone-anchored hearing aid is a type of hearing aid based on bone conduction. It is primarily suited to people who have conductive hearing losses, unilateral hearing loss and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids...
: 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. Another study showed that sound localisation was not improved, but the effect of the head shadow was reduced.
Hearing issues
When wearing stereoSTEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
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
STEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
to mono
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
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.