Unilateral Hearing Loss

Unilateral hearing loss, especially when it’s severe, presents two primary physical issues that are difficult to overcome. First, sound input to only one ear presents disadvantages for specific communication tasks, most notably sound localization and speech understanding in noisy settings. The second issue is that current device options can’t restore hearing to the impacted ear to achieve bilateral input or binaural processing.

A unique study analyzing unilateral hearing loss in adults revealed commonly encountered physical and psychological difficulties that impact quality of life. The underlying causes for hearing loss among the 14 people were diverse, including meningitis, head trauma, absence of the auditory nerve, tumors, otosclerosis, Meniere’s disease, virus, mumps, measles, and noise exposure. Among the participants, 44% currently used a hearing device, while 32% reported they had hearing loss since birth. This study uncovered important insights about the struggles associated with unilateral hearing loss.

• Congenital vs acquired hearing loss: Individuals born with hearing loss developed comparatively excellent coping mechanisms (e.g. lip reading, sign language, and favoring their good ear), experienced greater acceptance of their condition, and perceived less impact on their quality of life. In contrast, individuals with acquired hearing loss reported greater impact on their quality of life, including experiencing panic at the onset of hearing loss, struggling to adjust, and problems accepting the consequences of losing hearing in one ear.
• Functional impacts: The two most commonly reported functional impacts were difficulty listening in noise and poor localization. One participant said they had a hard time telling what direction sound comes from when they couldn’t see the source of the noise. Another said they felt almost blind on the left because they had no sense of someone being there. Another common issue was fatigue caused by straining to hear what people were saying.
• Psychological impacts: Most participants said hearing loss impacted their mental health, including fear and anxiety about how other people would treat them. Hearing loss caused feelings of depression, isolation, difficulties in social situations, and a decrease in self-esteem.
• Social/behavioral impacts: Communication problems in social situations led to isolation, resulting in issues with friends, as well as close family members. Frequently asking people to repeat themselves was a source of frustration that discouraged voicing their needs to others. Many cited a lack of societal awareness about unilateral hearing loss as a reason why other people weren’t empathetic about the daily challenges posed by their hearing impairment.
• Stigma in the workplace: A common concern was fear that colleagues would judge them, which resulted in trying to hide their hearing loss. One participant said, “I fear that if I have a hearing aid, people will automatically assume that I am fully deaf or incompetent to perform my job.”

An ability to localize and separate different sound sources is extremely important, often playing a crucial role in guiding behavioral responses (e.g. running away from a scary, barking dog). A large number of studies have demonstrated the importance of binaural hearing in localizing sound sources, and in improving the perception of target sounds in the presence of other interfering noises. Neurons in the auditory centers of the brain are tuned to cues that regulate intensity and timing differences between your two ears. The good news is research indicates some people with unilateral hearing loss may be able to compensate by becoming more dependent on unaltered cues available to their non-affected ear.

Recent magnetic resonance imaging (MRI) studies in people with unilateral hearing loss suggest hearing impairment is associated with network abnormalities and widespread involvement of various brain regions. A 2018 study found alterations to multiple large-scale networks involved in sensory and higher-level cognitive functions in individuals with long-term unilateral hearing loss. And researchers theorized these alterations are likely dependent on a person’s stage of deafness and hearing levels. Additional studies are needed to identify the precise brain mechanisms and alterations involved in hearing loss, which may guide the development of new treatments.

Meningitis: Inflammation of the meninges, the layers surrounding the brain and spinal cord is caused by a viral or bacterial infection. Although bacterial meningitis is more common in children, it can also affect adults. When hearing loss occurs, it’s due to inflammation that damages part of the inner ear.

Head trauma: Due to its sudden and violent nature, head trauma may cause damage to any point within a person’s auditory pathway. This damage can result in conductive and sensorineural hearing loss, central auditory processing deficits, balance issues, and tinnitus. The eardrum, middle ear, and inner ear are the most common sites of peripheral injury because they are often directly in line of the trauma.

Auditory nerve abnormality: Absence or deficiency of the cochlear nerve is associated with congenital sensorineural hearing loss in one or both ears. High-resolution magnetic resonance imaging (MRI) techniques are used to determine what nerves are present and their relative size.

Tumors: Unilateral hearing loss is a hallmark symptom of acoustic neuroma (vestibular schwannoma), a benign tumor that grows on the eighth cranial nerve. Paraganglioma, the most common primary tumor of the middle ear can cause ringing in the ears and prevent sound waves from passing through the middle ear to your eardrum, resulting in conductive hearing loss in one ear. And squamous cell carcinoma, the most common cancer of the external ear canal, can result in unilateral conductive hearing loss.

Otosclerosis: This progressive condition, is an abnormal growth of bone in the middle ear. The condition affects women more often than men, and at least 50% of cases are familial. Although bilateral ear involvement is far more common, up to 15% of cases are unilateral. The abnormality can disrupt the ability of sound to travel from the middle ear to the inner ear, resulting in hearing loss.

Meniere’s disease: Although the primary symptom is extreme dizziness, this disease can also cause tinnitus, the sensation of blocked or muffled hearing, and a feeling of congestion, fullness, or pressure in the affected ear. If your inner ear fills with excessive fluid, this can damage the delicate hair cells, resulting in permanent hearing loss.

Viruses: Many viruses can cause congenital or acquired hearing loss that is unilateral or bilateral. Most often, this is sensorineural hearing loss that damages the inner ear structures. Cytomegalovirus (CMV), a common virus that can infect people of any age, is responsible for up to 40% of all congenitally acquired hearing loss. Other viruses associated with hearing loss include rubella (German measles), measles, mumps, HIV, herpes simplex virus, West Niles virus, and varicella zoster virus.

Mumps: While this is often considered a childhood disease preventable through vaccinations, it can impact unvaccinated adults. When mumps causes hearing loss, it is often profound, unilateral sensorineural hearing loss that doesn’t respond to treatment. In a 2017 Japanese study on 66 patients, the oldest participant was 54-years-old and the majority had never been vaccinated.

Noise exposure: Largely preventable, exposure to noise is one of the most common causes of sensorineural hearing loss. While you might assume this type of hearing loss impacts both ears uniformly, many studies show people suffer from asymmetrical hearing loss, resulting in significantly worse hearing loss in one ear. A 1993 study found that 80% of participants had unilateral hearing loss from noise exposure, while a 2010 study showed 22.6% of participants had asymmetrical hearing loss. People who shoot guns for sport and truck drivers are particularly susceptible to hearing loss due to noise exposure. 

Contralateral Routing of Signals (CROS) hearing aid: Designed specifically for unilateral hearing loss, this device consists of a microphone placed at the impaired ear, which then routes the acoustic signal to a hearing aid worn in the normally functioning ear.

Bilateral microphones with contralateral routing of signal (BiCROS) hearing aid: This variation on the CROS hearing aid is an option when a person has asymmetrical hearing loss, with substantially better hearing in one ear than the other.

Bone-anchored hearing aid (BAHA): Combining a sound processor with a small titanium fixture implanted behind your ear, this unique system allows the bone to transfer sound to your functioning inner ear instead of via your middle ear. A 2017 study found that individuals with unilateral hearing loss achieved significant improvements in speech-in-noise ability for both CROS and BAHA hearing aid systems, with no difference between the two methods.

Cochlear implant: This is a small implanted electronic device used in cases of severe to profound hearing loss that can’t be treated with hearing aids. An external portion sits behind your ear with a second element surgically placed under the skin. The device works by bypassing damaged hair cells in your inner ear and directly stimulating the auditory nerve to send information to your brain. The MED-EL USA Synchrony cochlear implant system for single-sided deafness and asymmetric hearing loss was approved by the FDA in July 2018. This cochlear implant helps address issues that other hearing devices for unilateral hearing loss can’t, including localizing sound and the ability to hear in noisy environments.

If you’re experiencing hearing loss in one ear, it’s important to speak to a licensed hearing professional right away. In some cases, treating the underlying cause can resolve hearing loss. Even when hearing loss is permanent, working with an audiologist to find the most optimal treatment option will help you adjust to this major change and live life to the fullest.