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Those whose hearing is impaired
literally live in a world of their own, what with their
inability to hear sounds and speeches unaided. SOLAADE
AYO-ADERELE examines the latest hearing gadgets that are
supposed to restore hearing to the deaf.
THE world of
the deaf is an unfamiliar one to those who can hear well. In
place of the ‘normal’ conversation, they gesticulate, making
use of the American Sign Language, which is the dominant sign
language of the hearing-impaired. In Nigeria, the ASL is used
alongside indigenous sign language. And, like any sign
language, its syntax and grammar are distinct from any spoken
language in its area of influence.
Hearing families
with deaf children often adopt ad hoc ‘home sign,’ an
idiosyncratic set of hand gestures, for simple
communications.
Yet, language defines us as human. Hearing
is how we learn speech. As we learn our language as children,
we use that language to organise how we see the world. Hearing
is how we best receive the speech sounds that contain the
ideas, feelings and personalities of other humans. If an
individual loses his hearing, he loses a bit of his
humanity.
According to a clinical audiologist, Dr.
Simeon Afolabi, of the Hearing and Speech Consult, the human
ear performs the task of translating the analogue sound waves
in air into digitised nerve impulses in the organ of hearing.
“The process of hearing involves two principal stages,” he
said.
“First, the sound waves travelling in the
air are reproduced in the fluids of the cochlear portion of
the inner ear. The structures which accomplish this task
include the outer ear, the ear passage, and the ear drum and
bony chain.
“The next phase of hearing
involves the hair cell array in the organ of Corti of the
cochlea, which analyses the waves and converts them into the
complex digital code carried by the nerve of hearing to the
brain. Additional stages of hearing include the brain, which
constantly adjusts the cochlea, depending on what we intend to
hear.”
He explains that there are two overall types of
hearing loss: conductive and nerve hearing losses. Afolabi
says conductive hearing losses are caused by anything
interfering with the first stage of sound
processing.
“Conductive losses make the sounds seem
faint or distant. When the sound source is made louder, the
hearing loss is completely overcome. Often, the hearing loss
is accompanied by a feeling of blockage,” the audiologist
says.
Common causes of conductive hearing loss include
wax in the outer ear passage and fluid in the middle ear.
Other conditions include otosclerosis, which jams the bony
linkage between the ear drum and the inner ear. It can also be
caused by damage to the ear drum or bony chain as a result of
chronic infection.
According to experts,
conductive losses almost always can be repaired by either
medicine, surgery or a combination of both.
“The structures
involved in a nerve hearing loss (otherwise called
‘sensorineural’ or ‘perceptive’ hearing loss) include the
cochlea and the eighth cranial nerve, which are locked away
inside the bones at the bottom of the
skull.
“In addition to affecting the loudness
of hearing, nerve hearing loss produces distortion of the
sounds entering the ear. Someone with this kind of loss may be
aware of sounds, but makes errors deciding exactly what sounds
represent. People with a nerve hearing loss experience
difficulty decoding the complicated sounds we string together
to make speech,” Afolabi explains.
Nerve hearing loss
almost always affects the high frequencies first; as such, in
noisy situations, people with a nerve hearing loss have the
greatest difficulty.
Until recently, most of these losses
were attributed to old age, experts say. However, they add
that the tendency to develop these losses probably runs in
families and is aggravated by the noise pollution in our
society.
People with a nerve loss have problems
communicating with friends and family. Though they hear what
is being said, they often hear it incorrectly and having a
conversation becomes very difficult. Often, families give up
trying to get through to the person who has a nerve loss. For
the person with a nerve hearing loss, a public gathering such
as a party or a performance is a disaster. Often, the person
with a nerve hearing loss begins to avoid going into public
without realising why.
However, to make social
integration possible for the hearing-impaired in a hearing
society, scientists have continued to device various hearing
gadgets to aid the moderately to the profoundly hearing
impaired person to live the day to day life.
During a
chance encounter with the marketing coordinator of Cochlear
AG, manufacturers of some of the latest and highly rated
hearing devices globally, Mr. Riccardo Licari, he explained
that before now, the thought was that hearing impairment could
not be corrected surgically. “That has changed for good,” he
said.
Unlike its predecessors in the world of hearing
aids, Licari said the cochlear implant was a technological
triumph. “It is the only medical device designed to restore a
human sense of hearing and is an alternative to traditional
solutions like hearing aids, which often provide little or no
benefit for someone with severe to profound hearing loss,” he
explained.
“A hearing aid works by amplifying
sound. However, for those with the most severe hearing loss,
amplification often does not improve hearing because the ear
itself does not function properly. Rather than making sound
louder, a cochlear implant bypasses the damaged part of the
ear and sends sound directly to the auditory (hearing) nerve.
This provides a clearer understanding of sound and
speech.”
According to Afolabi, the surgical
process involving the fitting of cochlear implant in a patient
is quite simple and lasts for just an hour when done by a
skilled surgeon, as the implant is surgically placed under the
skin behind the ear.
The basic parts of the device,
Licari explained, included the external: a microphone which
picks up sound from the environment; a speech processor which
selectively filters sound to prioritise audible speech and
sends the electrical sound signals through a thin cable to the
transmitter; and a transmitter, which is a coil held in
position by a magnet placed behind the external ear, and
transmits the processed sound signals to the internal device
by electromagnetic induction.
The internal parts
include a receiver and stimulator secured in bone beneath the
skin, which converts the signals into electric impulses and
sends them through an internal cable to
electrodes.
Here, an array of up to 24 electrodes wound
through the cochlea, which send the impulses to the nerves in
the scala tympani and then directly to the brain through the
auditory nerve system.
Afolabi corroborated
this, saying, “A cochlear implant is an
electronic medical device that replaces the function of the
damaged inner ear. Unlike hearing aids, which make sounds
louder, cochlear implants do the work of damaged parts of the
inner ear (cochlea) to send sound signals to the
brain.”
Licari explained the uniqueness of their
star product, the Nucleus CI500 Series of cochlear implants,
saying it is the world’s thinnest cochlear implant, at 3.9 mm.
“Built on leading implant reliability, it is 40 per cent
slimmer than the previous generation. Its enhanced implant
strength makes it two and a half times stronger when compared
to previous generation Nucleus implant, the Nucleus
Freedom.
“The Nucleus CI500 Series contains the largest
number of real, active electrodes, powered by a
custom-designed microelectronics platform — for the most
precise stimulation, and accurate delivery of sound to the
hearing nerves,” he explained.
There are a number of
factors that determine the degree of success to expect from
the operation and the device itself. Cochlear implant centres
determine implant candidacy on an individual basis and take
into account a person‘s hearing history, cause of hearing
loss, amount of residual hearing, speech recognition ability,
health status, and family commitment to aural
rehabilitation.
Though the devices come at a princely sum,
Licari said wealthy Nigerians and non-governmental
organisations should come to the aid of their countrymen by
donating money to organisations that help the hearing
impaired; or, by adopting a patient, outright, for cochlear
implants.
This tallies with the request of Mrs.
Tina Okelue, who is a guardian to Master Clinton Ekweremadu, a
hearing impaired child. Okelue appealed to the government and
public-spirited individuals to help parents by subsidising the
high medical costs of treating their hearing challenged kids,
to make social integration possible for them in a hearing
world.
Afolabi and Licari couldn’t agree
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