Cochlear Implant Outcomes in Adults and Children with Inner Ear Malformations

Szudek J1, Dettman S2, Sadeghi-Barzalighi A2, Zraika L2, and Briggs RJS1 1University of Melbourne, Department of Otolaryngology, 2University of Melbourne Department of Audiology

Introduction Bony cochlear or vestibular malformations occur in about 20% of patients with congenital sensorineural hearing loss. Intuitively, one would expect such malformations to influence surgical and audiologic outcomes in patients undergoing cochlear implantation. However, the precise impact of these malformations on surgical and audiologic outcomes has not yet been elucidated.

Patients and Methods

A retrospective review of the Cochlear Implant Clinic database at the University of Melbourne identified 57 children and 31 adults with cochlear and/or vestibular malformations who had undergone cochlear implantation. The patients’ CT and MRI scans were classified into ordinal categories of cochlear malformation according to the scheme of Sennaroglu1: common cavity (CC), incomplete partition -I (IP-I); IP-II with or without enlarged vestibular aqueduct (EVA); IP-III, or EVA alone. Analysis of variance (ANOVA) was used to compare speech perception (open-set word, phoneme and sentence scores), language development (Peabody Picture Vocabulary Test (PPVT) standard scores and delay), and surgical outcomes (occurrence of a CSF gusher and insertion depth) among the groups of malformations. Pearson’s correlation coefficients were calculated between the duration of profound hearing loss and speech perception and language outcomes. T-tests were used to compare speech perception and language outcomes between groups of patients with and without gushers and incomplete electrode insertions. SPSS5 was used to perform all statistical analyses.

Results - Adults

Table 3: Outcomes in Adults by Type of Congenital Malformation

Duration of profound hearing loss was significantly correlated with OSW Word (r=-0.36, p=0.04) and BKB Sent (r=-0.41, p=0.02), but not with OSW Phon (r= -0.27, p=0.14), . Table 4: Outcomes in Adults with Gushers and Incomplete Insertions Discussion Pre-operative imaging is a routine and essential part of planning cochlear implantation. However, based on this retrospective study of children and adults , the extent of pre-operative cochlear/vestibular malformation alone cannot predict post-operative cochlear implant performance (Tables 1 and 3). On the other hand, the presence of gusher, incomplete insertion and a longer duration of pre-implantation hearing loss were associated with worse speech perception and language outcomes in children and adults (Tables 3 and 4). Of the 11 gushers encountered in children, 4 were accompanied by an incomplete insertion. Of the 5 gushers encountered in adults, all had a complete insertion. The only incomplete insertion in an adult did not have a gusher. This suggests that only part of the speech and language outcome may be related to incomplete insertion. Only one adult had incomplete electrode insertion, precluding meaningful statistical comparison (Table 4) The post-operative speech and language scores in the present study are similar those reported in other pediatric groups with cochlear abnormalities but lower than those with normal cochlea and adult groups.2-4

One of the limitations of this study is the significant number of patients who did not have complete post-operative speech perception and language testing. For example, 2 of the patients with common cavities, 5 of those with IP-II + EVA and 2 of those with EVA alone performed too poorly to test OSW. This may contribute to the failure of this study to show performance differences between groups of different malformations. On the other hand, the patients with these malformations who were tested performed well, underscoring the wide range of outcomes that we observed within all groups of malformations

Conclusions !   Implant performance cannot be reliably predicted based on the type of radiographic

cochlear malformation in either children or adults.

!   Implant recipients with a shorter period of profound hearing loss have significantly better implant performance.

!   Intra-operative gushers and the incomplete insertions are associated with worse implant performance

References 1.  Sennaroglu L. Cochlear implantation in inner ear malformations--a review article. Cochlear Implants Int.

2010;1:4-41 2.  Van Wermeskerken GKA, Dunnebier EA, Van Olphen AF, Van Zanten BA, Albers FW. Audiological

performance after cochlear implantation: a 2-year follow-up in children with inner ear malformations. Acta Otolaryngol 2007;127:252–257.

3.  Dowell RC, Dettman SJ, Blamey PJ, Barker EJ, Clark GM. Speech perception in children using cochlear implants: prediction of long-term outcomes. Cochlear Implants Int 2002a;3:1–18.

4.  Gleeson, T.G., Lacy, P.D., Bresnihan, M., et al. High resolution computed tomography and magnetic resonance imaging in the pre-operative assessment of cochlear implant patients. J Laryngol Otol 2003;117, 692-695

5.  SPSS Base 20 for Mac. IBM SPSS Statistics. 2011

Results - Children

Table 1: Outcomes in Children by Type of Congenital Malformation

“Other” malformations in Table 1 included two IP-I cochlea, one hypoplasia and one unclassified malformation. Duration of profound hearing loss was significantly correlated with OSW Phon (r= -0.43, p=0.004), OSW Word (r=-0.32, p=0.03), BKB Sent (r=-0.35, p=0.02), and PPVT delay (r=0.49, p=0.001) but not with PPVT SS (r=-0.25, p=0.1). Table 2: Outcomes in Children with Gushers and Incomplete Insertions