Objective:
Cochlear implantation in patients with residual hearing can lead to hearing loss (HL)
caused by e.g. inflammation. Preserving hearing is essential in patients who are candidates
for combined electric and acoustic stimulation (EAS). Glucocorticoids are one possibility
to counteract loss of residual hearing. GGA has been successfully tested to alleviate
noise induced HL and age related HL. GGA is a non-toxic inducer of HSF1 which inhibits
inflammatory cytokines.
Methods:
Two groups of hearing Guinea pigs were implanted with a custom-made electrode (MED-EL).
GGA or ringer solution was infused via cochleostomy before using a micro-syringe pump.
The second ear was treated likewise omitting implantation. HL was tested before and
after application at day 0, 3 and 7 postop by measuring click evoked CAPs and frequency
specific CAP audiograms via electrodes implanted near the round window. Additionally
electrode impedances were determined for the implant contacts at each time point.
Results:
Differences found between GGA and control group were not statistically significant.
However, there was one visible trend: CAP-thresholds were higher at all frequencies
at day 0 in the GGA treated group but decreased to lower thresholds compared to controls
at days 3 and 7. Similar results but with less HL were found at the control side.
There was also a trend for lower impedances in the GGA group. HL at the implanted
side of both groups showed a gradient from high (30 – 40dB) at the base to low frequencies
(5 – 15 dB) at the apex.
Conclusions:
Although not significant, the slight decrease of CAP thresholds and impedances suggests
that GGA might have the potential to preserve hearing after implantation. Higher dosage
and/or sustained drug application could enhance the efficacy.
