الفهرس 
Maturation of cortical auditory evoked potentialsOnly 14 pages are availabe for public view
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Abstract
Auditory evoked potentials provide an objective measure of the brain’s responses to sound and are tools that can be used to assess aided
as well as unaided auditory function in children (Purdy, 2001). From
birth up to 7 years of age the CAEP response is dominated by a large, late
P1 response (Ponton et al., 1996). In normal hearing children, the latency
of the P1 decreases systematically as age increases (Sharma et al.,
2002b).
So this study will research the validity of the P1 response to assess
hearing aids by providing information about the maturation of central
auditory pathway (Sharma et al., 2005).
The present study included 200 children with age range of 3 – 6 years.
They were divided into two groups. The control group is consisted of 50
volunteers with normal hearing, matching in age and gender the study
group. The study group is Consisted of 150 children ranged in age 3-6
years old with sensorineural hearing loss. They were divided into three
groups; Group (a); well hearing aid fitted group. Group (b); poorly fitted
group and Group (c); not wearing hearing aids.
All children were submitted to full history taking, psychosocial
evaluation, otological examination, basic audiological evaluation and the
Auditory cortical evoked potentials test. The instruments used were; Two
channels pure tone and speech audiometer model Madsen ( orbiter 922
version I) calibrated according to ANSI (1969), Sound treated room
(model amplisilence), Tympanometry GSI (tempstar model), auditory
evoked response audiometer using Intelligent Hearing system (model
Smart EP two channels), A laptop Compaq for playing cartoon movies
Summary
Page 70
for the children. The test of CAEP is performed serially each month for
aided children for 15 months.
P1 wave dominated the CAEP appeared in 100% of the children.
But N1 wave in contrast did not appear in all individuals of our control
group. In the study group (a); P1 it appeared as a big positivity but with
longer latency. This latency decreased with the period of hearing aid
usage till reaching to the normal values after 15 months of using the
hearing aids.
N1 wave only started to appear at 9 months post fitting of the hearing
aid in 32% of the children with delayed latency than that of the control
group that was reduced with wearing hearing aids till approaching normal
data after 15 months of using the hearing aid. But amplitude at 9 months
did not change significantly with the regular use of the hearing aid.
While children of the group (b) were poorly fitted so benefit will be
more less with less improvement of the latency of P1 wave by using the
hearing aids (N1 wave did not appear at all). In group (c); Only very few
children gave results (8%) for P1 with delayed latency with no N1 wave.
from the data obtained in the previous control group and the study
subgroups we found that; P1 is affected in the latency and amplitude due
to hearing loss, P1 is a reliable method for judgement of the hearing aid
or any amplification device due to; It Appears in 100% of the normal
population ( So any absence will reflect HL or defected hearing), Change
regularly with hearing compensation, The degree of amplification affect
the degree of the wave development, The satisfactory amplification reach
with the P1 development to match that of the normnormal values of the P1
wave. But N1 wave in contrast is not a reliable wave.