1 Epidemiological data
Hearing loss is a public health issue.
For instance,
its prevalence in France is 11% (according to the study of the French Research Center on the psychosocial aspect of disability in August 2010),
of these,
360 000 have profound or total hearing loss (5 per 1000 people).
Elderly people are much more likely to have a hearing impairment than younger people.
As more and more people live to older ages,
the prevalence of chronic conditions that cause functional impairment is expected to increase.
2 Disease severity
Hearing impairment is very common among elderly people and can seriously affect their quality of life,
personal safety,
and ability to function independently.
It can also interfere with important activities of daily living (according to U.S.
Congress,
Office of Technology Assessment,
Hearing Impairment and Elderly People–A Background Paper,
May1986).
Indeed,
one third of people with hearing loss need help in their day-to-day activities.
3 Cochlear implantation indication
Cochlear implants can be helpful and are being used by people with severe-to-profound sensorineural hearing loss in both ears and who no longer benefit from hearing aids.
Candidates to implantation in adults should have a clear understanding of cochlear implantation (CI) and end results.
They should also be motivated and committed to the process and follow-up appointments.
There is no upper age limit for cochlear implantation in adults.
4 What is a cochlear implant and how does it work?
Cochlear implants are medical electronic devices that bypass damaged structures in the inner ear and directly stimulate the auditory nerve.
They are surgically implanted into the cochlea,
the hearing organ of the inner ear.
A microphone,
processor,
and transmitter are worn externally to control the implanted internal device.
The transmitter is located behind the ear and overlies the implanted stimulator,
being held in place by a magnet attached to the implanted stimulator (Fig. 1 Fig. 2).
Cochlear implants convert sound waves to electrical impulses and transmit them to the inner ear,
where the spiral ganglion cells of the cochlea are stimulated.
The number of electrode varies between different brands (15 to 24 electrodes).
Each electrode is tonotopic which means that each electrode is placed at a specific location of the cochlea to address a specific frequency range.
Cochlear implants can be either in one ear or in both.
5 Audiometric definition of severe to profound hearing loss
Severe to profound bilateral sensorineural hearing loss is defined by specific audiologic criteria for cochlear implantation.
It is met when speech discrimination is less than 50% open-set sentence recognition with properly fitted hearing aids.
6 Etiologies of bilateral sensorineural hearing loss in adults
The main etiologies of bilateral sensorineural hearing loss in adults are:
- Genetic deafness (progressive disease of the young)
- Presbycusis: is the term most often used to describe hearing impairment in elderly people.
It is usually defined as a sensorineural loss caused by changes in the inner ear
- Acoustic trauma
- Toxic deafness
- Other: traumatic,
infectious and inflammatory diseases,
acoustic neuroma,
cholesteatoma ...
7 Indications of the bilateral implantation:
Any cause of deafness with short-term risk of bilateral cochlear ossification,
mainly in bacterial meningitis or fracture of the temporal bone.
The patient must be operated as soon as possible before the ossification reaches an advanced stadium.
Bilateralization is indicated in adults,
who are losing a benefit from the conventional amplification in the non implanted side,
causing socio-professional consequences or loss of autonomy.