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The effects of extended preoperative systemic steroids in hearing preservation cochlear implantation
Kuthubutheen J. , Coates H. , Rowsell C. , Chen J. , Nedzelski J. , Lin V.
Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada, 2University of Western Australia, School of Surgery, Perth,
Intro: Steroids have been shown to reduce the hearing threshold shifts associated with cochlear implantation.
However at present, studies have only examined the administration of steroids just prior to surgery. It is well
known that steroid effects are dependent upon the duration of exposure. The aim of this study is to examine the
role of extended preoperative systemic steroids in hearing preservation cochlear implantation.
Methods: An animal model of cochlear implantation was used. 24 Hartley strain guinea pigs with a mean weight
of 768 g and normal hearing were randomised into a control group, a group receiving systemic dexamethasone
one day prior to surgery and a group receiving steroids 5 days prior to surgery. A specially designed cochlear
implant electrode by MED-EL (Innsbruck) was inserted through a dorsolateral approach to an insertion depth of
5mm and left in-situ. Auditory brain stem responses at 8kHz, 16kHz and 24 kHz were measure preoperatively,
and 1 week, 1 month and 2 months postoperatively. Cochlear histopathology was examined at the conclusion of
the study.
Results: At 1-week post op, the group receiving dexamethasone 1 day prior to implantation had lower threshold
shifts across all frequencies and which was significant at 32kHz (p< 0.05). The group receiving steroids 5 days
prior to surgery had significantly lower shifts at both 32kHz and 16 kHz (p< 0.05). At 1 month, both steroid
groups had lower threshold shifts compared to control and from 1 month to 2 months, both steroid groups
maintained their thresholds compared to control (p< 0.05). The 1 day prior steroid group had less fibrosis
compared to control at 2 months post-surgery (0.29mm vs.0.42mm ), p=0.08. The high frequency selectivity of
systemic steroids suggests maximal effects around the basal turn of the cochlea. Further histopathology results
will be presented.
Discussion: This is the first study to demonstrate the benefits of extended preoperative steroids on hearing
outcomes in cochlear implantation surgery and its predilection for effects in the basal turn of the cochlea in the
animal model. This may mean that when high frequency hearing has been lost, the effect of systemic
preoperative steroids may not be seen.
Conclusion: The high frequency selectivity of preoperative systemic has implications for considering the
concept of “complete steroid coverage” where steroids are used before, during and after implantation. Steroids
not only reduce the threshold shift but maintain it post cochlear implantation.
Learning objectives: To discuss the role of preoperative systemic steroids on hearing outcomes in the animal