Most people with hearing loss have what’s known as “binaural” hearing loss, meaning both ears are affected. But some people may lose their hearing in just one ear. This can develop either at birth or later in life.

This is known as unilateral hearing loss or single-sided deafness, depending on the severity of the hearing loss. It’s generally referred to as “single-sided deafness” (SSD) when the degree of hearing loss is profound or near-profound. More on degrees of hearing loss.

The hearing loss can occur gradually or suddenly. When it happens suddenly, it requires prompt treatment and should be considered a medical emergency. This is known as sudden sensorineural hearing loss.

Single-sided deafness (SSD) is when one ear is completely ineffective or there seems to be no usable hearing from that side. For example, a person with SSD may have normal hearing in one ear without any hearing in the other ear, while someone else with SSD may have some hearing in their ear with hearing loss, however, it is not enough sound to be considered helpful with understanding conversations.

Unilateral hearing loss means that there is some amount of hearing loss in one ear, but not necessarily a complete loss of hearing, like single-sided deafness. People with UHL could have a mild hearing loss in one ear, which is therefore, not considered deafness.

unilateral hearing loss or single-sided deafness,

How hearing loss in one ear affects hearing

We were designed to have two ears for a reason—the brain uses both ears to pinpoint the location of a sound, and to improve hearing quality and range.

Losing hearing in one ear presents unique challenges. Depending on the severity of your hearing loss:

  • You can’t always pinpoint where a sound is coming from: Your brain knows where a sound is coming from by which ear receives the sound first, known as sound localization or directional hearing. When a person can only hear well from one ear, he or she may have difficulty figuring out where the sound originated.
  • You may struggle to hear in noisy environments: Your brain is in charge of selective listening, meaning, filtering out noises that aren’t useful. This is tougher to do without the aid of a second ear. In a noisy environment, a person with SSD can struggle to focus on a single person’s voice.
  • You may have a harder time telling how loud a sound is: The brain “hears” a sound more loudly when it’s perceived through both ears than if the same sound at the same decibel were only perceived through one ear. This is because the brain receives signals from the nerves located in both ears and uses this information to process sounds.
  • You may struggle to multi-task: Because of all of the above, single-sided deafness increases cognitive load on the brain, leading to listening fatigue. The more noise there is, the longer it takes your brain to focus on the tasks at hand. If you’re also trying to listen to someone speak, you may miss a significant amount of what is being said.

The ‘head shadow’ effect of single-sided deafness

If you have single-sided deafness, you will likely experience something known as the “head shadow” effect. Due to the way sound waves travel, high-frequency sounds don’t “bend” around to the side of the functional ear, meaning a person never hears them.

The head essentially acts as a shield, blocking sounds from the poorer hearing ear from reaching the better hearing ear. The end result is that speech can sound muffled, because a person can’t hear high-frequency sounds like “s” or “f.”

Causes of hearing loss in one ear

You can be born with unilateral hearing loss, or it can be progressive, meaning it develops over time. Unilateral hearing loss (UHL) that is acquired later in life can happen from certain illnesses, like viruses or autoimmune diseases, or can happen idiopathically which means, without a known cause. Congenital UHL or hearing loss in one ear that you are born with, can occur spontaneously, without having any risk factors at birth, or it can be caused by craniofacial differences, family history, or an associated syndrome. There are a number of potential causes of hearing loss in just one ear, including but not limited to:

  • Meniere’s disease
  • acoustic neuroma
  • viral or bacterial infections
  • physical damage to the ear and head trauma
  • circulatory system disorders
  • genetic or inherited disorders

Sometimes a cause can’t be identified or is due to a combination of factors.

What Are the Symptoms of Unilateral Hearing Loss? 

Those who have unilateral hearing loss have reduced awareness of sound on the affected side. This may also be joined by unilateral tinnitus, or the perception of sound when there is not an external source. Research (Persson et al, 2001; Shaw and Vaillancourt, 1985) has shown that our brains rely on hearing from both ears to help us hear best in background noise and to localize where a sound is coming from. Acquired UHL has been associated with embarrassment, frustration, anxiety, insecurity, and social isolation due to sudden change in quality of life.

Sudden hearing loss in one ear

Hearing loss in one ear can develop quickly—you should always act fast if you or a loved one experiences sudden hearing loss of any severity. As it develops, you may also notice you have “double hearing,” known as diplacusis.

You should always seek medical care ASAP if you experience sudden hearing loss.

The quicker you seek treatment, the better your chances are for a full recovery. When hearing can’t be fixed with medical treatment, single-sided deafness is often the result, which happens about 15% of the time.

How Is Unilateral Hearing Loss Diagnosed? 

Unilateral hearing loss is diagnosed by an audiologist with a comprehensive hearing evaluation. For children, a screening at birth, at the pediatrician’s office, or at school can detect a possible unilateral hearing loss, which should be confirmed with thorough testing by an audiologist.

Some signs of unilateral hearing loss in children can present as increased listening effort, poor behavior, and poor academic performance. If you notice these in your child, consider ruling out hearing loss as a contributing factor.

For adults, if unilateral hearing loss is sudden in nature, immediate appointments to their primary-care or an ear, nose, and throat physician is essential. The emergency room is another option, but many times the correct medical care and diagnosis are missed because most emergency rooms are unable to evaluate hearing.

How Is Unilateral Hearing Loss Managed and Treated? 

The management and treatment of unilateral hearing loss depends on the degree of loss, as well as the degree of impact on daily life. If the unilateral loss is sudden in nature, the success of medical treatment depends on how quickly treatment is administered after onset of symptoms. Sudden hearing loss should always be immediately evaluated by an otolaryngologist, more commonly known as an ear, nose, and throat physician (ENT).

If the hearing loss is longstanding and if medical treatment is not an option, unilateral hearing loss can be treated with different technologies based the person’s needs and hearing loss qualifications. In conjunction with technology, good communication strategies should be used for people with UHL, as they may need an adjusted environment to succeed in speech understanding. Consider reducing background noise on the good side and enhancing speech on the good side.
For people with mild to moderate hearing loss, a hearing aid may be all that’s needed to amplify the sounds you’re not hearing.

Severe to profound single-sided deafness is often permanent, but sometimes treatable with devices worn on your functioning ear. Your audiologist will perform a hearing test, and ask you questions to try and identify the cause of your hearing loss. From there, he or she might recommend a Hearing aid, CROS, BiCROS, or bone-anchored hearing system:

  1. Hearing Aid
    • If appropriate, research supports the use of amplification on the affected ear. Hearing aid use has been shown to allow for improved access to conversation, balance of sound, and sound awareness.
  2. CROS Hearing Aid
    • For those who have hearing loss that cannot be helped with a traditional hearing aid, a CROS system can be considered. A CROS (contralateral routing of sound) system looks like a hearing aid, but does not send any sound into the affected ear. Rather, it uses a microphone to pick up sound on the side of the person’s head with the hearing loss and sends it over into a device worn on the good ear. Though this cannot help to restore sound localization, this allows improved awareness of sound on the affected side.
    • CROS Hearing Aidbi CROS Hearing Aid
  3. Bone-Anchored Implant
    • A bone-anchored implant (BAI) can be considered for unilateral hearing loss, though the success of certain goals may depend on the degree and type of hearing loss in the affected ear. Hearing loss that is conductive or mixed in nature, meaning there is some abnormality in the ear canal or middle ear space, may have good success with a BAI for balance of sound. For single-sided deafness, a BAI would route the sound to the better hearing ear, acting similarly to a CROS device. As the BAI typically requires surgery, a non-surgical CROS device should be trialed first.
    • bone-anchored implant (BAI)
  4. Cochlear Implant
    • For children who are born with severe to profound UHL, a cochlear implant can be considered; however, language and cognitive delays for young children are unlikely if they have one ear with normal hearing. For UHL that is acquired later in life, the success of cochlear implantation can depend on age, duration of hearing loss, and severity of hearing loss, so a full evaluation with an audiologist and otolaryngologist who specialize in cochlear implantation for individualized recommendations is encouraged.
    • cochlear implant
  5. Remote Microphone/ FM system
    • A remote microphone, previously known as an FM system, can also be considered a treatment option for UHL. This device can be helpful when the speech of interest is at a distance or in the presence of background noise.
    • Remote Microphone/ FM system

Who Should I Call if I Suspect Unilateral Hearing Loss? 

If you suspect unilateral hearing loss, consider consultation with an audiologist and otolaryngologist (ENT). If the unilateral hearing loss is sudden in nature and happens spontaneously throughout the day or upon waking up in the morning from sleep, immediate evaluation by an ENT is strongly recommended, as timing of treatment can affect recovery of hearing.

For longstanding unilateral hearing loss, consider consultation with an audiologist for baseline hearing evaluation and discussion of effects on communication and treatment options. If you or someone in your family suspect hearing loss, Find an Audiologist near you to set up an appointment.

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