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Cochlear Implant Evaluation -- Promontory Stimulation Test

Eric Smith erc at cinenet.net
Sun Sep 3 01:39:33 EST 1995

In article <428d94$opq at news.cc.utah.edu>,
Loren Randolph <Loren.Randolph at m.cc.utah.edu> wrote:
>The following info is based on about 80 stims:
>1. Poking sensation is probably from promontory electrode in wrong
>place, stimulating 7 or 10 cranial nerves. Need to reposition
>electrode during testing until proper  (acoustic) perception attained.

According to the audiologist who operates the prom stim equipment,
the equipment has an indicator on it to tell when the electrode is
in the right place.  But the poking sensation happened regardless,
and at the same time sound was perceived.

>2.. Short term, adaptation probably not significant, but we have
>noticed that thresholds tend to rise with time. (Longest implant pt
>here, with Symbion-Richards-Cochlear Corp implant = 12 years)

Do you mean the thresholds rise with time in those patients who had
the adaptation, but not in other patients?  Can you give an example,
in dB per year, or some such figures, of the threshold rise for a
specific patient, to make it clearer how much of a factor it is?

I have been told that the adaptation is something the prom stim test
is looking for, and that it might be a contraindicator for a CI.

>3. lack of ucl could relate to safeguards in stimulator, of lack of
>ucl in pt. I wouldn't get real excited about it, as long as pt can
>perceive increase in loudness with increase in amplitude

Have you observed specific cases of lack of ucl?  How common does it
seem to be?

>4. Balance problem likely related to local anesthetic.  We initially
>thought that auditory (electrical) stim could cause stim of only one
>side of vestibular system, thus vertigo, but it has never happened.
>We do, however, keep a large trash can handy during the prom test
>because of the anesthetic, and insist that the patient bring a driver.

Excellent idea.  Better than sending the patient to the emergency
room when it happens.  :-)

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