Cochlear implantation in cochlear nerve deficiency: A systematic review

Objectives

Our goal was to review the current literature to better understand outcomes following cochlear implantation (CI) in patients with cochlear nerve deficiency (CND).

Data sources

PubMed, MED-LINE, and Google Scholar.

Review methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol, PubMed, MED-LINE, and Google Scholar were queried for articles published from January 2000 to December 2023 describing cochlear implantation in patients with cochlear nerve agenesis or deficiency.

Results

Of 1820 articles initially identified, 28 articles met inclusion criteria, amounting to 514 patients and 513 cochlear implantations. Among the 24 studies that differentiated between cochlear nerve hypoplasia (CNH) and aplasia (CNA), there were 154 ears with hypoplasia and 364 ears with aplasia. The most common outcome measured was Categories of Auditory Performance; other outcomes used by multiple studies included hearing threshold, Meaningful Auditory Integration Scale, Meaningful Use of Speech Scale, and Speech Intelligibility Rating. The average pre-operative CAP was 0.5, and the average post-operative CAP was 3.6. The average pre-operative hearing threshold was 101.3 dB, and 85.5 % of participants had no response on pre-operative auditory brain response. The average post-operative aided hearing threshold was 42.5 dB, with 4.2 % of patients showing no response.

Conclusions

CI in children with CND offers the potential for significant improvement in hearing threshold and speech development, but outcomes are variable in those with more profound nerve hypoplasia or aplasia. Families should be counseled pre-operatively on the possibility of limited results and the potential benefit of alternative treatments like auditory brainstem implantation.