by Theresa Brassard, Audiologist
This article was prepared for the Support and Information
Meeting of the
Canadian Hyperlexia Association,
April 2, 1998.
Normal hearing is essential for effective
communication and interaction
with our environment via the auditory modality.
An impairment in "hearing"
impedes our ability to understand the spoken message
and/or listen
effectively. To most, hearing refers only to
the ability to perceive
sounds. True hearing involves not only the
physical ability of the ear to
detect sounds, but to the ability to integrate and
assimilate the acoustic
information in our environment. Auditory
processing, the higher order
function of hearing, enables "sound localization and
lateralization,
auditory discrimination, auditory pattern
recognition, temporal aspects of
audition including temporal resolution, temporal
masking, temporal
integration and temporal ordering; auditory
performance with acoustic
signals and auditory performance with degraded
acoustic signals."
(ASHA 1996,p.41).
Physiologically, auditory stimuli i.e. sounds
reaching the cochlea, are
encoded and transmitted along neurological
pathways. Interactive
brain/neural networks assimilate the information from
multiple sources to
interpret the pattern of acoustic stimuli and
ultimately the message.
Inaccurate/incomplete coding or transmission of the
acoustic signal may
result in aberrant processing of the auditory
information. An auditory
processing deficit refers to impaired function in one
or more of the above
noted auditory processes.
Recent research has postulated three different
types of neurophysiological
deficits which underlie childhood central auditory
processing disorders
(CAPD):
1) neuromorphological disorder (areas of
underdeveloped, misshapen and/or
misplaced cells in the left hemisphere or auditory
areas of the corpus
callosum). This group represents 65-70% of
those diagnosed with CAPD;
2) maturational delay of the Central Auditory Nervous System (25-30%); and
3) neurological diseases, disorders and insults (less than 5%).
In addition, CAPD can co-exist with many other
conditions including
hyperlexia, Attention Deficit Disorder, language
impairment, learning
disabilities, dyslexia, autism, PDD, aphasia and/or
children with a history
of chronic otitis media.
Central auditory processing disorders exist in
children with normal hearing
as well as in children with hearing losses. A
peripheral hearing test
(audiogram and test of middle ear pressure) does not
rule out a CAP
Disorder.
Children with CAP disorders may exhibit one or more of the following behaviours:
* difficulty attending in group
situations;
* difficulty understanding and/or following
directions;
* difficulty understanding persons who speak
quickly;
* difficulty understanding/extrapolating the main
point from the speech message;
* difficulty organizing actions and sequencing
ideas;
* difficulty localizing sounds;
* difficulty sequencing letters within words when
speaking, reading;
* phonetically, spelling, writing and comprehending
what they read;
* easily distracted by sounds in the
environment;
* easily overloaded by auditory
information;
* frustrated when presented with a lengthy speech
message;
* unable to remember oral information;
* misunderstands/mishears words; and/or
* sensitive to sounds
Children with auditory processing disorders
frequently try very hard to
understand the spoken message and become confused,
angry and/or frustrated
when they are unsuccessful. CAP disorders often
impede a child's ability
to interact with their peers as they often cannot
understand the rules of
the game or phrases the other children use. All
of the above points will
be exacerbated by the presence of other conditions
i.e. language
impairment.
Diagnosis of a CAP disorder is essential for the
implementation of
appropriate therapeutic and/or remedial
strategies. Formal diagnosis is
accomplished through administration of a battery of
tests, each designed to
stress various behavioural processes required to
process auditory
information i.e. the ability to filter our background
noise. Although
general information can be obtained as early as 5 1/2
- 6 1/2 years of age
the administration of the comprehensive CAP test
battery is not performed
until the age of 6 1/2 - 7 years or later to minimize
any bias introduced
by limited vocabulary and/or attention.
In younger children, informal
diagnosis is made utilizing behavioural information
in conjunction with
speech language measures.
Once diagnosed as having a CAP disorder there are
several approaches which
can be taken to assist the child. The
traditional approach has been
through the implementation of compensatory strategies
both at home and at
school. These can include:
* cueing the child prior to speaking with
him/her;
* speaking at a slow to moderate rate;
* being specific and using concrete
language;
* presenting multi-step instructions or lengthy
information in stages; and/or
* eliminating background noise/distractions.
In the classroom, some children find a FM or
similar system useful. For
many children, however, this is not enough; they may
need direct
interventions e.g. metacognitive and metalinguistic
training, auditory
training and/or more recently the use of a programme
designed to teach the
brain to process temporal and spatial cues more
effectively.
The ability to accurately process the auditory
information in our
environment is essential for full interaction with
the world around us. A
weakness in the area of CAP can impede a child's
speech language, cognitive
and emotional development. Identification of a
CAP weakness is the first
step towards minimizing the impact of this
disorder.
Theresa Brassard is an audiologist in private practice at the
Hearing
Health Centre in Toronto.