An explorative study on cortical activation in normal hearing and in deaf adults, before and after cochlear implantation, measured with fMRI and NIRS.

A cochlear implant (CI) is a implantable electronic device that provides
hearing sensations to patients with profound or total sensorineural hearing
loss. Most of the children and postlingually deafened adults have favourable
outcomes after implantation, however the benefits provided by CI*s display a
great variability in adults who lost their hearing ability before the
development of speech and language, the so-called *pre-lingually deaf*
candidates. The prediction of substantial communication benefits after cochlear
implantation is still a clinical dilemma. Until now, no objective tests have
been described to predict the outcome of implantation in this pre-lingual
patient group. Previous studies suggest that probably PET could be used to
assess glucose-metabolism in the auditory cortex pre-operatively in order to
predict postimplantation CI results. However, this imaging technique has the
disadvantage that patients had to be injected with an isotope.

To examine brain activation in the auditory cortex, without using an isotope,
functional Magnetic Resonance Imaging (fMRI) can be an effective tool. Probably
an fMRI scan can be used as an effective non-invasive tool to predict the
postoperative hearing performance with CI. After implatation, probably NIRS
can be used to investigate the hemodynamic response.

A relation is expected between hearing performance in implanted (pre-lingually)
deaf patients on the one hand and cortical hemodynamic response on the other.

The primary objective of the present study is to increase our insight in the
neural processing in pre-lingually deaf and implanted patients, regarding the
prediction and explanation of postoperative differences in performance within
this specific group of cochlear implant users. To that end we will investigate:
a. the predictive value of brain hemodynamic response, measured by fMRI, on
postoperative behavioural responses in pre-lingually deaf patients with
residual hearing (study A)
b.If NIRS can be used as objective tool for evaluating the cortical activity in
implanted patients (study B)

Two explorative studies:

Study A
In order to investigate the predictive value of brain hemodynamic response 10
pre-lingually deaf candidates for cochlear implantation will be evaluated one
month before surgery. Also a normal hearing group will be measured, in order to
relate cortical hemodynamic responses of prelingually deaf patients with normal
hearing subjects.

In one scan-session 3 conditions will be measured: without stimulation, with
auditory stimulation and with visual stimulation.

Study B
In order to investigate the differences in hemodynamic response between
between good and poor performers with CI and to relate these results to normal
hearing subjects, three groups will be investigated: 10 pre-lingually deaf
implanted patients with a good result, 10 pre-lingually deaf implanted patients
with a poor result, 10 normal hearing healthy volunteers. Each subject
participates 1 NIRS measurement. During the measurement 3 conditions will be
investigated: without stimulation, with auditory stimulation and with visual
stimulation.

For both measurements no risks are expected.