Single-sided Deafness in hearing health influences a person’s emotional and physical health. Hearing loss, even in one ear, is associated with other problems which can range from balance to social and behavioural issues.
What is Single Sided Deafness (SSD)?
Single-Sided Deafness (SSD) or Profound Unilateral Hearing Loss refers to a condition where an individual has non-serviceable hearing in one ear and normal hearing in the other ear. A non-serviceable ear is defined as one with no usable hearing even with the use of a hearing aid. In an audiometry report, it is commonly referred to as profound hearing loss where an audiometry test is able to determine the degree of hearing loss.
What happens in SSD?
In the mechanism of hearing, sound waves travel through the outer ear to the middle ear, inner ear (cochlea), auditory nerve and eventually to the brain. In SSD, the damage is normally located at either the cochlea, or the auditory nerve. The injury at the outer ear and the middle ear, even to its maximal extent, will not cause SSD.
What causes SSD?
The causes of one-sided hearing loss could be as simple as impacted earwax, or as sinister as nasopharyngeal carcinoma or acoustic neuroma. There is no one specific cause but some possible ones include:
• Viral infection causes direct injury to the cochlea
• Blunt trauma to the head injure the inner ear structure
• Vascular insult decrease the blood supply to the cochlea
• Brain tumour e.g. acoustic neuroma
• Side effect of drugs affecting the inner ear or auditory nerve (ototoxicity)
• Congenital malformation of the inner ear
• Meniere’s disease
• Autoimmune disease
How is SSD detected?
An ENT doctor will normally perform a thorough examination but it is not uncommon to be unable to identify a cause in some situations. An MRI brain scan is always performed on adults to rule out acoustic neuroma, a benign tumour arising from the auditory nerve.
If you think you are experiencing one-sided hearing impairment (not only confined to SSD), please consult an ENT specialist as soon as you can. In a condition called Sudden Sensorineural Hearing Loss (sudden loss of hearing in one ear or both ear), if the treatment is delayed for more than two weeks from the onset of the symptoms, the hearing loss could turn permanent.
What happens to the senses of a person with SSD?
A patient with SSD will be able to hear with the good ear but will experience difficulty in localising the source of the sound. During a conversation, the patient will have a tendency to turn his or her head to direct the good ear towards the person who is speaking, in order to get a clearer sound. In a noisy environment, the person will find it hard to focus on a single person’s voice
How is SSD treated?
There are two ways to achieve binaural hearing – one is by rerouting the sound from the poor ear to the good ear, and the other is to restore the auditory function by inserting an implant. Rerouting the sound can be done through air (air conduction device) or through bone (bone conduction device).
For an air-conduction device, there is the CROS (contralateral routing of signal) system. The patient wears a behind-the-ear or in-the-ear device that mimics a hearing aid at both the ears.
The bone conduction system involves surgically implanting a device at the skull bone behind the non-serviceable ear. Alternatively, a person can use a stick-on bone conduction device which does not require surgery.
Restoring auditory function can only be achieved by performing surgery. There are two types of surgery – cochlea implant or brainstem implant, depending on the site of the lesion/damage. A cochlea implant bypasses the damage at the inner ear while a brainstem implant bypasses the damage at the inner ear and auditory nerve.
Single-Sided Deafness (SSD) is now listed as a disability by Malaysia’s Social Welfare Department (JKM).
In 2019, the Social Welfare Department (JKM) recognised SSD as a disability. The JKM registration form (pindaan 2/2019) is now available online at JKM.
By DR CHAI CHIUN KIAN AND DR TANG MEE LING / SUNWAY MEDICAL CENTRE VELOCITY
