Single sided deafness

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SINGLE SIDED DEAFNESS – HEARING THE OTHER SIDE

Last summer, Entific Medical Systems completed the second stage of UK research to establish the problems experienced by people with single sided or unilateral deafness. As part of this research they assessed the benefits of the BAHA device (a bone anchored hearing device) to people with Single Sided Deafness as a result of acoustic neuroma.

The findings show that many people live with a wide range of problems as they struggle to cope with the loss of hearing in one ear. Many find the loss of the stereo effect derived from hearing with two ears, leaves them with an ’acoustic shadow’ such that sound originating from their poor side is missed. This is particularly noticed at meetings or out at a restaurant when someone persistently talks form one side. There are also problems of sound localisation, such that it is difficult to determine the origins of noises. Not only is this socially embarrassing but it can present dangers when out alone in determining the direction of traffic - over half of the people in the study experienced difficulties when out as a pedestrian. Worryingly, many people also found that SSD has affected their ability to work - in some cases to the extent that they have either had to give it up, move to lighter work or go part time.

Despite this, in the UK Single Sided Deafness is still not formally recognised and as a result many people are not receiving treatment that could dramatically improve their quality of life.

Single Sided Deafness refers to complete sensorineural hearing loss in one ear and in most cases it is a permanent condition. Extrapolating figures from the United States, where the condition is formally recognised, it is estimated that up to 9,000 people develop SSD in the UK each year.

Causes of Single Sided Deafness
Single Sided Deafness may be a result, symptom or side effect of a number of different conditions. Sudden deafness is the most common condition to result in Single Sided Deafness but many cases are not recorded as patients either fail to present to their GP or, in some cases, patients are not referred to ENT for further investigation and treatment. Therefore, it is impossible to be certain of the total number of new cases of sudden deafness each year.

Acoustic neuroma is another but much rarer condition that results in SSD and it is estimated that it accounts for only a small percentage of SSD cases per year. However, though rare, acoustic neuroma is a widely studied condition and as a result, data exists on the impact of SSD on acoustic neuroma patients.

Diagnosis and treatment
Depending on the symptoms experienced, most patients will initially contact their GP who should then refer the patient to an ENT or Neurological Consultant who will arrange for an audiologist to assess the patient and determine the treatment. Investigating SSD further is essential for accurate diagnosis and prompt treatment of some conditions, for example, Single Sided deafness can be an indicator for acoustic neuroma. Single Sided Deafness is diagnosed using standard hearing tests but other diagnostic tests to ascertain the cause of SSD might include a CT scan and MRI scan.

Single Sided Deafness can be treated, irrespective of the length of time a patient has suffered from hearing loss and three out of five people with SSD would like the opportunity to receive treatment that could improve their hearing and therefore their quality of life.

Finding a new indication for Single Sided Deafness: a study of acoustic neuroma patients by Through the Loop for Entific Medical Systems

Once in the secondary care system, patients with Single Sided Deafness receive the same priority for treatment as patients with bilateral deafness and will join the same waiting list for treatment as patients with bilateral deafness. Ideally, eligibility for treatment of SSD should be partially assessed on the extent to which the hearing loss is a disability, on an individual basis. Therefore, consultants and surgeons often rely on patients to articulate the scale and severity of their own disability; treatment is not necessarily recommended for all.

One of the most recent devices indicated in the treatment of SSD is the BAHA® – a bone anchored hearing device.

Diag 1: Stimulation pathways to the cochlea in a patient with SSD on the left side fitted with a BAHA® sound processor.

The BAHA® System
BAHA received FDA clearance for the treatment of Single Sided Deafness in 2002. It has also been cleared to treat SSD when patients cannot, or for any reason will not, use a CROS aid. BAHA is a semi implantable bone anchored hearing device. The BAHA has been available for over 25 years for all traditional conductive hearing loss indications, whether unilateral or bilateral, and over 11,000 people have been treated with BAHA worldwide. To date over 400 patients with Single Sided Deafness have been treated using BAHA in Europe and the USA.

The BAHA device provides a unique benefit to people with SSD by enabling the user to hear and understand sounds from both sides of the head where previously they could only hear sounds from the direction of their good ear.

How does it work?
The BAHA device works by conducting sounds from the deaf side through the bone of the skull to the hearing ear. The head shadow effect is no longer a problem and this ultimately results in the sensation of hearing from the deaf side.

The BAHA device has three main parts - an external sound processor, an abutment and a small titanium implant, which is placed in the skull bone behind the deaf ear. The sound processor transfers sound to the titanium implant and in this way, the vibrating sound waves become directly connected to the skull. The sound waves then travel through the skull bone to the inner ear on the hearing side. Minor surgery is needed to fix the implant but this is often done under a local anaesthetic and patients leave hospital the same day. The external sound processor clips onto a small abutment so it can be easily removed and the whole device is easily hidden by hair.

If you would like to learn more about BAHA and its potential benefits as a solution to Single Sided Deafness, please contact your local hospital or ENT consultant or visit www.patient-baha.com or www.entific.com.

Acoustic neuroma
An acoustic neuroma is a slow growing, benign tumour of the auditory nerve. The condition is very rare and there are approximately 13 newly diagnosed cases, per million of the population, per year. The cause of an acoustic neuroma is not known.

About 80% of patients with an acoustic neuroma will suffer from sensorineural hearing loss as their initial symptom. The hearing loss is usually gradual but in approximately 5% of cases, patients present as sudden deafness. The loss of hearing is due to a compression of the auditory nerve by the tumour. Some patients may present with good hearing but lose their hearing on one side following surgical intervention to remove the tumour. Other treatments, such as Gamma Knife, may not result in total hearing loss on one side.

In addition to a decline in hearing quality, other symptoms of acoustic neuroma may include facial sensations or tingling, loss of taste, loss of balance, watering eyes, severe headaches, aching teeth and a clicking jaw. In most cases, hearing is not restored after treatment.

(source: British Acoustic Neuroma Association )

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28/3/03