Inter-aural hearing preservation in cochlear implantation
Reviewed by Kerri Millward and Morag Lockley

Hearing preservation during cochlear implantation is becoming increasingly important, although results can be unpredictable. NICE are in the process of updating their guidance in the UK and it is possible that those with better hearing than the current candidates will be considered for implantation. The cochlear implant team at RNTNE investigated inter-aural hearing preservation in their older paediatric population (age six to 18 years). All underwent simultaneous implantation using a MED-EL FLEX 28 implant using the round window approach and ‘super slow’ technique. There were seven patients identified, making 14 ears in total. All of these patients were deemed to have hearing that might be preserved (maximum thresholds of 105dB HL at 250Hz and 110dB HL at 500Hz and 120dB HL at 1000Hz) rather than being identified as electro-acoustic stimulation candidates. Hearing preservation percentages were calculated using the formula described by the HEARRING group. Preservation is described as complete (>75%), partial (25-75%) and minimal (0-25%). Hearing preservation was achieved in 86% of cases but only two patients had inter-aural hearing preservation within the same preservation group. Examining inter-aural hearing preservation allows each patient to act as their own control so factors such as implant type, technique, surgeon and auto-immune response can be eliminated as a cause of postoperative hearing loss. Surgeon factors such handedness of surgeon and surgeon fatigue were not shown to have an effect. The authors therefore concluded that minor surgical variation, such as insertion angle, depth and rate as well as small anatomical variation, could also be an explanation for the inter-aural hearing preservation differences found in this study.

Evaluating inter-aural hearing preservation in bilateral paediatric cochlear implantation.
Jones HAS, Powell HRF, Hall A, et al.
COCHLEAR IMPLANTS INTERNATIONAL
2018;19(6):307-11.