Unilateral Hearing Loss & Single-Sided Deafness

Many people with hearing loss usually find both ears afflicted with this condition. When hearing loss is diagnosed in both ears, it is known as bilateral hearing loss. Bilateral meaning “two sides”. Bilateral hearing loss can be caused by a range of factors, including old age, exposure to loud noises, certain medications, infections, and diseases. All these factors lead to the damage or loss of specialised cells in the ear that are responsible for detecting sound. These specialised cells are also known as inner ear hair cells. When hair cells die off, they cannot be replaced. Modern medicine has not yet found a way to reliably regrow this hair cells as a form of treatment. Bilateral hearing loss affects the ability to hear sounds coming from all directions, resulting in poor understanding of speech in noisy environments, and trouble participating in conversations with multiple talkers.

On the other hand, hearing loss can also affect only one ear. This is dubbed unilateral hearing loss. Unilateral meaning "one side". Unilateral hearing loss can be present at birth or acquired later in life. The presence of hearing loss in one ear at birth can be caused by anatomical defects in the ear or through ear nerve damage. Acquired unilateral hearing loss can come about by trauma to the head, infections or growth of a tumour. Unilateral hearing loss can occur in either ear and the degree of loss in the affected ear can range anywhere from mild hearing loss all the way to profound hearing loss. When the degree of hearing in the affected ear is so severe that it becomes non-functional even with the help of hearing aids, it is termed single-sided deafness.

What many fail to realise is that single-sided deafness (SSD) can have a significant impact on individuals' daily lives and communication abilities. Problems arise because even though they have a normal-hearing ear on one side, the other side of the body lacks a functioning ear. This leads to a phenomenon called the head-shadow effect where an individual’s head effectively blocks sounds reaching the good ear from the deaf side. We shall explain the head-shadow effect with an analogy below.

Let’s take taxi driver Bob as an example. Bob is diagnosed with unilateral hearing loss because he has severe hearing loss in the left ear but normal hearing in his right ear. So, Bob cannot hear clearly in the left ear and has to rely heavily on the right ear to listen in daily life. When a passenger who is seated on the left talks to Bob, Bob cannot hear well from the left ear and additionally, his head blocks some of the sounds reaching the functioning right ear. This results in miscommunication which not only upsets Bob, but ends up delivering his passenger to the wrong location. Bob later decides to quit being a taxi driver and withdraws into his home to avoid interacting with people.

People living with unilateral hearing loss like Bob experience a ton of setbacks in daily life. These problems range from the inability to locate a person calling your name to  keeping up with conversations in noisy places and can lead to increased frustration, isolation, and risks to personal safety. Another potential risk is not noticing an approaching vehicle from the deaf side, which increases the likelihood of an accident. The main goal of treatment is to avoid situations such as these. Fortunately, there are potential solutions for those with single-sided deafness. In the next article, we will explore the treatments for unilateral hearing loss and single-sided deafness. If you suspect you or your loved ones are suffering from hearing loss, please reach out to an audiologist or ENT to be tested as soon as possible. Take care of your hearing and your hearing will take care of you.


Written by: Patrick Seow, Clinical Audiologist at 20dB Group