Single sided deafness (SSD) is a type of unilateral hearing loss wherein an individual has profound hearing loss in one ear and normal or almost normal hearing from the other ear. Typically, SSD is a permanent condition.
The challenges faced by someone with SSD are quite different than those experienced by someone with bilateral hearing loss. In ideal listening conditions, such as sitting face-to-face at close distance in a quiet room, understanding speech is fairly easy, because in such a scenario the signal from each ear is mostly redundant. The brain is able to function fine with the input from a single ear. This is why most people are able to have a phone conversation even though they are hearing the phone call in only one ear.
The situation in a restaurant, shopping mall, city park or car is very different. In these settings, there will usually be multiple sources of sound at any particular moment, and some of them will be just as loud as the conversation someone is focusing on. In this case, the brain needs two ears working together to be able to filter out the background noise and understand the primary speech signal. Someone with SSD will find it difficult to carry on a conversation in noisy places.
Someone with SSD will typically have difficulty localizing sound (recognizing the location or origin of a sound source) and hearing speech coming from the same side as the affected ear. Sound localization depends on subtle differences in the hearing cues from each ear.
Complications of SSD include anxiety, stress, social isolation, dizziness and difficulty maintaining attention.
What Causes Single Sided Deafness?
SSD can be caused by a variety of factors and can develop slowly or very rapidly.
Sudden deafness is a rapid onset of hearing loss that occurs with little or no warning, often following a viral infection. This type of hearing loss will often affect only one ear and cause SSD.
Additional causes of SSD include:
- Trauma to the head
- Genetic disorders
- Meniere’s disease
- Eighth nerve tumors
- Microtia
- Mastoiditis
- Measles
- Mumps
Treatments for SSD
The unique challenges created by SSD require unique treatment options as the objectives are different than those for bilateral hearing loss. There are two widely accepted technological solutions for SSD:
- Contralateral Routing of Signal (CROS) hearing system: A CROS system looks essentially identical to a pair of hearing aids. It utilizes a microphone that is placed in the vicinity of the impaired ear and an amplifier near the normal ear. The microphone picks up sounds and transmits them to the patient’s good ear. The BiCROS variant is suitable for individuals with some degree of hearing loss in one ear and total deafness in the other.
- Bone Anchored Hearing Aid (BAHA): a surgically implanted device that uses direct bone conduction to transmit sounds through the skull from the affected side to the normal side. Vibrations in the bones of the ear canal and middle ear stimulate the hair cells of the cochlea, boosting the ability to hear.
When treating SSD with one of these two options, there is almost always a significant improvement in speech understanding for speech coming from the affected side, but localization remains difficult. Great improvement in the ability to understand speech in noisy backgrounds can be realized by the use of an accessory microphone that beams a wireless signal directly to the CROS system or BAHA.
In 2019, the FDA approved the use of a cochlear implant to treat SSD. Several research studies have demonstrated that it can approve speech understanding in noise and localization, but it will likely be considered experimental by most insurance carriers for some years to come. Because it requires invasive surgery and uses electrical stimulation of the auditory nerve, cochlear implants are only appropriate in very specific cases for now.
If you think you have SSD and are interested in our personalized recommendation on treatment, call our office at (808) 262-6673 to schedule an appointment.
