Single sided deafness

Single sided deafness

Updated 2020

Single sided deafness and asymmetrical hearing loss.

Single sided deafness (SSD) is the condition where a patient has normal hearing in one ear and deafness in the other ear. Deafness is defined as hearing loss of such a severity that a patient cannot benefit from a conventional hearing aid (non-serviceable). It can be said that SSD is the most severe form of unilateral hearing loss.

Asymmetrical hearing loss refers to bilateral hearing loss but which substantially differs between the two sides.

Single sided deafness

A Bonebridge is an excellent option for single sided deafness


How common is single sided deafness?

Unilateral hearing loss affects about 5% of the general population. About 5 out of 1000 children suffer from SSD. It is estimated that 60 000 patients are diagnosed with this condition in the USA every year

What causes single sided deafness?

SSD may be present from birth (congenital) or develop later in life. The main cause of congenital SSD is an abnormal or absent cochlear nerve. The second most common cause is congenital cytomegalovirus (CMV). Genetic causes may also be responsible. In many cases, the cause for the congenital SSD remains unknown.

The most common cause of acquired SSD in adults is idiopathic sudden onset sensorineural hearing loss(SSNHL). As the word, idiopathic implies the reason is still not known. Virus infections and circulatory problems may be responsible.

Other causes include ear infections, cholesteatoma, meningitis, Meniere’s disease, and vestibular schwannoma. Viruses are known to cause single sided deafness and include mumps, shingles, herpes simplex (HSV-1), and HIV. Surgical removal and radiation of vestibular schwannomas/acoustic neuromas can also cause SSD.

Head trauma causes deafness due to bleeding in the inner ear or a fracture of the temporal bone. In older patients and those with cardiovascular risk factors, a small clot or spasm of a blood vessel can cause a “stroke” of the inner ear with hearing loss.

How does single sided deafness influence a person?

Patients complain of difficulty in localizing sound, following conversations in background noise, and hearing speech on the deaf side. Some patients may also suffer from dizziness and balancedizziness and balance problems. In smaller children, SSD can often go unnoticed. This is sad as it can influence the development of the child. Up to a third of children with SSD need to repeat a grade at school and children with SSD are more likely to need regular private teaching.

SSD also leads to problems with other sensory functions and the development of an internal model for 3D spatial orientation and awareness.

How is single sided deafness investigated?

Patients with SSD should see an ENT surgeon to rule out a possible underlying cause. A magnetic resonance imaging (MRI) may be requested to rule out a vestibular schwannoma. In cases of trauma, high resolution computed tomography (CT scan) can show a temporal bone fracture. In other cases, blood tests will be required.

What are the treatment options for single sided deafness?

There are many viable solutions for patients with SSD. Before one is chosen, all options should be discussed to determine which one best suits the challenges that a patient is experiencing.

The available options to improve hearing include frequency modulation (FM ) systems, soft band bone conductors, contralateral routing of signal (CROS), and bone-conduction transcranial CROS devices. Surgical options include bone-anchored hearing systems (Ponto or Bonebridge) and cochlear implantation (CI).

Cochlear implantation for single sided deafness.

Cochlear implantation is emerging as a very effective way of restoring SSD and in many studies proves to be one of the best options. Patients with a long history of hearing loss, even exceeding 35 years have shown benefit after CI. It is the only option that aims to restore binaural hearing, utilizing the cochlear nerve and pathways on the deaf side. CI is the best option to improve spatial orientation by using sound information for localization.  It may also suppress debilitating tinnitus that often accompanies SSD.