CharlieHarney at worldnet.att.net
Sat May 16 16:11:07 EST 1998
A good article to read for background is "Radiology of Congenital Hearing
Loss" in -The Otolayngological Clinics of America- Vol.27, #3, June 1994,
High resolution CT may give an idea of the condition of the cochlea.
The lack of a BC ABR response is a bummer. But please remember the
limitation of the frequency response of the bone conduction vibrator, which
is primarily in the mid frequencies. Low frequency hearing may be present,
which due to the limitation of air and bone conduction frequency specific
(I use Gorga's 250Hz tone pip for AC) stimuli, may not be obtainable.
In fitting the child initially try a the Phonak BTE that has the highest
output, (I think it is the PPCL-4) that can be modified by the company for
bone conduction. Assume some usuable hearing (<45dBHL thresholds) is
present at 1000Hz and below.
I first adjust the volume of the hearing aid by filling the ears of an
audiologist with earmold impression and then do sound field testing aided
and unaided.with the oscillator on the preferred mastoid.
The critical element is the position and force of the oscillator on the
mastoid. With the Phonak aid 30-35dB functional gain is possible with
sufficient force and proper placement at vol 3 wheel rotation ( at least
with my audiologist).
Finally I fudge at the beginning. I use Velcro. I stick a piece of Velcro
on the body of the BTE and have the parents prepare a"gorro" (the english
escapes me), a Velcro band around the head which holds the oscillator to
the mastoid and over the top of the head where the hearing aid will be
placed, the microphone facing toward the speaker.
It looks a little wierd but there is no problem with head shadow effect as
when the mic is at one ear, the child will not be pulling it off and he can
be lying in a crib awake and be receiving stimuli.
The down side is a loss of probably 5-10dB in output to the mastoid. (This
would be the same amount with a body H.aid w/mic placed on the chest). I
think the benefits outweigh the negatives.
Please make sure you plug up the parents ears and let them listen to the
hearing aid. They will be amazed at the quality of the speech and when you
demonstrate (applying more pressure) the importance of a tight fit they
will make the effort to have one.
I don't know how much this will help in your current situation, but good
San Juan, Puerto Rico
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