Outcomes for adult cochlear implant recipients with functional pre-operative hearing

Abstract

BACKGROUND & AIMS: In recent years, the population of persons with hearing loss attending cochlear implant (CI) centres for candidacy discussions has shifted to include those with greater hearing than in the past. Specifically, persons may have residual low frequency hearing ranging from normal to moderately severe with profound loss in the high frequencies (i.e. partial deafness (PD)). To support CI clinicians’ provision of evidence-based recommendations to adults with PD, new clinical outcome data, candidacy guidelines, and predictive factors associated with preservation of acoustic hearing are required to address the following: assessment of speech perception benefits for adults with PD using CIs, quantifying risk for loss of residual hearing, and evaluating outcome by electrode array type.

METHOD: This ambidirectional study design used a prospective cohort of adults with PD and two retrospective analyses of adults who received a CI at the Royal Victorian Eye and Ear Hospital (RVEEH).

To assess speech perception benefits for adults with PD as compared with traditional CI recipients (defined as severe-to-profound or poorer audiometric thresholds pre-implant), a group of 27 adults with PD were compared to a matched group of traditional CI recipients with all data sourced from the RVEEH database. All recipients were using perimodiolar arrays.

To assess hearing preservation outcomes, 154 adults with PD were studied prospectively. These adults were identified as proceeding with the device of interest, a CI with a thin straight electrode array (TSEA).

To assess speech perception outcomes by electrode array type, a group of 70 adults with PD using perimodiolar CIs sorted from the database were compared with a group of 63 adults with PD using TSEAs.

RESULTS: There were no significant differences in speech perception outcomes for adults with PD compared with those with profound hearing loss who received perimodiolar arrays.

Median change in low frequency hearing for adults with PD using a TSEA was -22.5 dB HL. Hearing preservation was assessed further for a subset of 78 defined as having ‘functional’ low frequency hearing pre-implant (≤70 dB HL). For persons who had a pre-implant low frequency pure tone median of ≤45 dB HL, functional hearing was preserved in 75% of cases.

No significant differences were found for speech perception outcomes based on electrode array type for the two groups of adults with PD. For persons using a TSEA, it was found that those who had preserved hearing and used electro-acoustic stimulation (EAS) performed significantly better than their peers with electric-only hearing.

CONCLUSION: The present study demonstrated that clinicians may use existing CI candidacy guidelines to counsel adults with PD who are considering a CI. The presence of low frequency hearing ≤45 dB HL pre-implant was associated with preservation of functional acoustic hearing in 75% of cases post-implant. Electrode array type was not found to be significantly associated with speech perception outcomes for adults with PD, however those that preserved hearing and used EAS demonstrated superior outcomes.

These data provide evidence-based guidelines for counselling adults with PD pre-implant with respect to their potential to benefit and the associated risks to hearing.