Cochlear implantation in patients with inner ear schwannomas: a systematic review and meta-analysis of audiological outcomes

Abstract

Purpose: In patients with inner ear schwannomas (IES), reports on hearing rehabilitation with cochlear implants (CI) have increased over the past decade, most of which are case reports or small case series. The aim of this study is to systematically review the reported hearing results with CI in patients with IES considering the different audiologic outcome measures used in different countries.

Methods: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, a search of published literature was conducted. We included patients with IES (primary or with secondary extension from the internal auditory canal (IAC) to the inner ear, sporadic or NF2 related) undergoing cochlear implantation with or without tumour removal. The audiological results were divided into the categories "monosyllables", "disyllables", "multisyllabic words or numbers", and "sentences".

Results: Predefined audiological outcome measures were available from 110 patients and 111 ears in 27 reports. The mean recognition scores for monosyllabic words with CI were 55% (SD: 24), for bisyllabic words 61% (SD: 36), for multisyllabic words and numbers 87% (SD: 25), and 71% (SD: 30) for sentences. Results from for multisyllabic words and numbers in general showed a tendency towards a ceiling effect. Possible risk factors for performance below average were higher complexity tumours (inner ear plus IAC/CPA), NF2, CI without tumour removal ("CI through tumour"), and sequential cochlear implantation after tumour removal (staged surgery).

Conclusion: Hearing loss in patients with inner ear schwannomas can be successfully rehabilitated with CI with above average speech performance in most cases. Cochlear implantation thus represents a valuable option for hearing rehabilitation also in patients with IES while at the same time maintaining the possibility of MRI follow-up. Further studies should investigate possible risk factors for poor performance. Audiological tests and outcome parameters should be reported in detail and ideally be harmonized to allow better comparison between languages.

Keywords: Acoustic neuroma; Cochlear implant; Inner ear schwannoma; Intracochlear; Intralabyrinthine; Neurotology; Schwannoma; Skull base surgery; Vestibular schwannoma.

Fig. 1

PRISMA flow chart

Fig. 2

Audiological outcomes with various speech material (mean and standard deviations): a Entire patient cohort (n = 110 patients and 111 ears), b sporadic IES and NF2-related IES; c tumours treated with microsurgical tumour removal and simultaneous or sequential CI and patients with cochlear implantation and tumour left in situ (“CI through tumour”), i.e., with observation or after radiotherapy. The number of available data are shown above the columns. Outcome measurements for different speech audiometry tests may belong to the same patient. A tendency for better CI performance in patients with sporadic IES (sentences) and for CI with tumour removal (monosyllables and sentences) but no statistically significant difference between the groups was found (t tests, all ps > 0.05). The time point of measurement is not considered here, which may introduce bias (compare Fig. 3). CI cochlear implant, NF2 Neurofibromatosis type 2 related schwannomatosis. Monos. Monosyllables, Disyl. disyllabic words, Multis./Numb. multisyllabic words or numbers. Senten. sentences

Fig. 3

Individual audiological outcomes of included population: a speech audiometry outcomes using monosyllabic word lists (n = 89), b speech audiometry outcomes using disyllabic word lists (n = 9), c speech audiometry outcomes using multisyllabic words and multisyllabic numbers (n = 21), d speech audiometry outcomes using sentences in quiet (n = 52). The grey area shows the "poor performers”, i.e., recognition scores of < 50% for monosyllabic and disyllabic tests or < 85% for multisyllabic words or numbers and sentences in quiet, respectively, after at least 12 months follow up (for definition: see methods). Numbers next to data points indicates multiple patients (ears) with the same outcome. CI cochlear implant, NF2 Neurofibromatosis type 2 related schwannomatosis

Fig. 4

Audiological outcomes based on tumour localization (mean with standard deviation): The number of available data are shown above the columns. Outcome measurements for different speech audiometry tests may belong to the same patient. A tendency for better CI performance in patients with intracochlear IES but no statistically significant effect of tumour location on mean recognition scores was observed (ANOVA, all ps > 0.05). The time point of measurement is not considered here, which may introduce bias (compare Fig. 3). IC intracochlear inner ear schwannoma (IES), IV intravestibular IES; IVC intravestibulococlhear IES; IE + IAC/CPA IES with primary or secondary involvement of internal auditory canal and/or cerebellopontine angle