Benefit from amplification of high frequencies in hearing impaire d

[Martin Vestergaard <MVE@xxxxxxxxx>]

Dear all, [Sorry for any duplication]

I'm pleased to announce the availability of the following PhD thesis:

Benefit from amplification of high frequencies in hearing impaired:
aspects of cochlear dead regions and auditory acclimatization

I you want a copy,
- for a pdf version, browse to www.at.oersted.dtu.dk/~mve/archives/
- for a printed copy, send me an email with your address

There's an abstract below!

Cheers,
MArtin


ps: if you've already asked me for a printed copy and you haven't received
it yet,
please send me an email with your current address

____________________________

Martin D. Vestergaard, PhD
Research Centre Eriksholm
Kongevejen 243
DK-3070  Snekkersten

Tel: +45 4829 8912




Abstract

The thesis deals with the benefit that hearing-impaired people receive from
amplification of high frequencies. Sounds brought back to audibility by
hearing aids are expected to provide usefulness for users of hearing aids in
terms of better auditory function, in particular better speech
identification ability. While the rationales underlying provision of
amplification to hearing-impaired patients are well-known, sometimes it
happens that audibility does not provide the expected benefit for the
patient. In the thesis, two theories are suggested for explaining why
audibility may fail to provide functional benefit to the users of hearing
aids: (1) cochlear dead regions and (2) auditory acclimatization. Two
studies have been carried out to assess the feasibility of the two concepts.
A study on cochlear dead-regions investigated the viability of a recent tool
for diagnosing dead regions and looked at the possible implications of
dead-region candidacy for speech-recognition ability in hearing-aid users
accustomed to high-frequency amplification. A second study on auditory
acclimatization in first-time hearing-aid users focused on longitudinal
effects in objective and subjective hearing-aid outcome for patients with
precipitous hearing loss.

The results show that the two theories to some extent can explain failure to
benefit from audibility. Patients with cochlear dead regions may not receive
increased benefit from increased audibility to the same extent as patients
without dead regions. However, dead-region patients show a more efficient
use of audibility leaving the reduced benefit from increased audibility less
salient in practice. Patients fitted with hearing aids that provide a
substantial amount of audibility, are able to improve auditory performance
over time. The strongest effect is seen in patients who initially do not
perform as well as expected. However, some severely impaired patients had
developed a better-than-expected ability to interpret low-frequency speech
cues. Age, severity of the hearing loss and cognitive skills can predict to
some extent if a patient is likely to improve auditory performance over
time. In the subjective-benefit domain, it is observed that outcome
dimensions addressed in various scales are not operational for hearing-aid
users right from the time of initial fitting. It can take up to 3 months
before a meaningful outcome space has been formed, and during that time, the
relative importance of different outcome scales changes. The clinical
ramification of the results from the two studies is threefold. First,
initial objective hearing-aid benefit may not reflect the level of auditory
performance that can be achieved after acclimatization to the amplification.
Second, early subjective outcome-assessment may not reflect the true
subjective benefit that the hearing-aid users experience. Third, possible
dead regions in the cochlea of patients may blur the situation in that
severely impaired patients may perform better than expected initially.