Asymmetrical hearing loss, also known as unilateral hearing loss, is when there is a significant difference in hearing (by more than 15 decibels) between the left and right ears. One ear may have “normal” hearing, while the other has a significant loss of hearing. There are three types of asymmetrical hearing loss:
- Asymmetrical sensorineural hearing loss – hearing damage in the inner ear
- Conductive hearing loss – sound is blocked and cannot move through the external ear or middle ear
- Mixed hearing loss – elements of both sensorineural and conductive hearing loss
There are a number of different causes for asymmetrical hearing loss to occur, including ear infections, trauma, exposure to loud noises, or certain medical conditions.
An ear infection can cause asymmetrical hearing loss and can take place in all three parts of the ear: the inner ear (just behind the eardrum), the middle ear, or the outer ear. The delicate structures of the ear can be damaged due to swelling and fluid build-up. Ear infections are treatable with antibiotics; however, there are severe cases where it may be required to drain the infected fluid to repair any damaged structures that may have occurred.
Asymmetrical hearing loss can be caused by exposure to loud noises. Noise levels exceeding 85 decibels are unsafe and can cause hearing damage. Even an impulse noise, such as a single loud blast or explosion that lasts for 1 second, can cause hearing loss. Exposure to loud noises can either damage or destroy the inner ear hair cells that give us our sensitivity to hearing sounds. Hearing loss can occur if the exposure to the sounds is intense or prolonged.
Trauma and ear injuries can also cause asymmetrical hearing loss. Trauma can include:
- Outer ear trauma – ex. foreign objects in the ear
- Middle ear trauma – ex. changes in air pressure
- Inner ear trauma – ex. hyperacusis
- Acoustic trauma – ex. Inner ear damage due to exposure to high-decibel noise levels
- Traumatic brain injury – ex. injuries from contact sports
- Post-traumatic Stress Disorder (PTSD) -ex. a terrifying event resulting in tinnitus
Lastly, certain medical conditions can cause asymmetrical hearing loss. For instance, Meniere’s disease, which is an inner ear disorder that causes vertigo, dizziness, problems with balance, and hearing problems like tinnitus, usually affects only one ear. Otosclerosis is another medical condition that causes hearing loss in one ear. Otosclerosis is the abnormal growth of bone inside the ear. Acoustic neuroma, also known as vestibular schwannoma, is a noncancerous slow-growing tumor that develops on the nerve that connects the brain to the ear, is another example. Autoimmune inner ear disease (AIED), an inflammatory condition in the inner ear, is another medical condition that can cause asymmetrical hearing loss.
Ear infections, trauma, exposure to loud noises, and certain medical conditions can cause asymmetrical hearing loss, a type of hearing loss where the hearing damage is more profound in one ear than the other. If you suspect you may have asymmetrical hearing loss, it is important to make an appointment with your doctor to get an evaluation and proper treatment.