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Comparison of the benefits of cochlear implantation versus contra-lateral routing of signal hearing aids in adult patients with single-sided deafness: study protocol for a prospective within-subject longitudinal trial

Pádraig T Kitterick12*, Gerard M O’Donoghue13, Mark Edmondson-Jones12, Andrew Marshall3, Ellen Jeffs3, Louise Craddock4, Alison Riley4, Kevin Green56, Martin O’Driscoll56, Dan Jiang7, Terry Nunn7, Shakeel Saeed8, Wanda Aleksy8 and Bernhard U Seeber109

Author Affiliations

1 National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, Ropewalk House, 113 The Ropewalk, NG1 5DU Nottingham, UK

2 Otology and Hearing group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, NG7 2UH Nottingham, UK

3 Nottingham University Hospitals NHS Trust, Queen’s Medical Centre, NG7 2UH Nottingham, UK

4 Midlands Hearing Implant Programme, Queen Elizabeth Hospital Audiology Centre, University Hospitals Birmingham, B15 2TH Birmingham, UK

5 Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, M13 9WL Manchester, UK

6 University of Manchester, Oxford Rd, M13 9PL Manchester, UK

7 Department of Audiology, St Thomas’ Hospital, Lambeth Palace Road, SE1 7EH London, UK

8 The Royal National Throat, Nose and Ear Hospital, 330 Gray’s Inn Road, WC1X 8DA London, UK

9 MRC Institute of Hearing Research, University Park, NG7 2RD Nottingham, UK

10 Technische Universität München, Associated Institute Audio Information Processing, Arcisstrasse 21, 80333 Munich, Germany

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BMC Ear, Nose and Throat Disorders 2014, 14:7  doi:10.1186/1472-6815-14-7

Published: 11 August 2014



Individuals with a unilateral severe-to-profound hearing loss, or single-sided deafness, report difficulty with listening in many everyday situations despite having access to well-preserved acoustic hearing in one ear. The standard of care for single-sided deafness available on the UK National Health Service is a contra-lateral routing of signals hearing aid which transfers sounds from the impaired ear to the non-impaired ear. This hearing aid has been found to improve speech understanding in noise when the signal-to-noise ratio is more favourable at the impaired ear than the non-impaired ear. However, the indiscriminate routing of signals to a single ear can have detrimental effects when interfering sounds are located on the side of the impaired ear. Recent published evidence has suggested that cochlear implantation in individuals with a single-sided deafness can restore access to the binaural cues which underpin the ability to localise sounds and segregate speech from other interfering sounds.


The current trial was designed to assess the efficacy of cochlear implantation compared to a contra-lateral routing of signals hearing aid in restoring binaural hearing in adults with acquired single-sided deafness. Patients are assessed at baseline and after receiving a contra-lateral routing of signals hearing aid. A cochlear implant is then provided to those patients who do not receive sufficient benefit from the hearing aid. This within-subject longitudinal design reflects the expected care pathway should cochlear implantation be provided for single-sided deafness on the UK National Health Service. The primary endpoints are measures of binaural hearing at baseline, after provision of a contra-lateral routing of signals hearing aid, and after cochlear implantation. Binaural hearing is assessed in terms of the accuracy with which sounds are localised and speech is perceived in background noise. The trial is also designed to measure the impact of the interventions on hearing- and health-related quality of life.


This multi-centre trial was designed to provide evidence for the efficacy of cochlear implantation compared to the contra-lateral routing of signals. A purpose-built sound presentation system and established measurement techniques will provide reliable and precise measures of binaural hearing.

Trial registration

Current Controlled Trials webcite (05/JUL/2013)

Cochlear implantation; Single-sided deafness; Unilateral hearing loss; Contra-lateral routing of signals; Hearing aid; Binaural hearing; Spatial listening