Hearing Preservation Cochlear Implantation: Balance and other considerations

Abstract

The University of Manchester Mark Felton, Doctor of Medicine, 2017 Hearing Preservation Cochlear Implantation: Balance and other considerations Background: Some cochlear implantation (CI) candidates have residual low frequency hearing. Hearing preservation (HP) CI with ‘soft’ surgery uses atraumatic CI insertion to limit intra-cochlear damage, preserving residual natural hearing. Objectives: To investigate the impact of ‘soft’ surgery on hearing preservation and balance outcomes, specifically: i HP outcomes in an adolescent population, if there is maintenance of any preserved hearing and, if so, the potential benefits of preserving this hearing; ii Reported long-term outcomes of HP CI surgery in paediatric and adult patients; iii Cochlear duct length (CDL) in a paediatric CI population and implications for electrode array insertion and HP; iv Balance function in previously- (PI) and newly- (NI) implanted adolescents and adults with reference to surgical technique. Methods: i HP outcome was measured with pre- and post-operative pure tone audiograms in 14 adolescents. Speech audiometry was also performed pre-CI and at subsequent follow-ups. ii A systematic review was undertaken of published literature (1946-2017) describing long-term (>12 month) outcomes of HP surgery in ≥10 patients, examining inclusion criteria, surgical techniques, outcome measures and assessments of long-term success. Of 1202 records identified via database searching, 22 fulfilled criteria for full-text analyses. iii A retrospective study was undertaken of 125 consecutive children undergoing CI, including 14 adolescents with HP surgery and 13 children with partial electrode array insertions, analysing electrode array, surgical details and audiological outcomes of HP. CDL was calculated from pre-operative imaging. iv. PI adolescents/adults (n=21) had balance function assessed by questionnaires, posturography, gait analysis and video head impulse testing (vHIT). NI patients (n=20) were tested pre-operatively and 1 month post-CI. Results: i HP was achieved in 13 of 14 adolescent CI (93%). Mean follow-up was 2 yrs 10 m (range 4 m-4 yrs 9 m). 3 of the 13 patients (23%) with initially successful HP had subsequent deterioration (>2 years later). Addition of natural preserved hearing to CI improved speech audiometry compared to implants in isolation (p0.05 for all). iv Overall, objective balance testing showed normal/maintained balance post-CI, but subjective questionnaires revealed clinically meaningful deterioration in dizziness symptoms post-operatively. HIT tended to decline post-operatively for ‘standard’ (non-soft) and cochleostomy approaches (p>0.05). Younger age was significantly correlated with greater HP (p

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Iain Bruce (Supervisor), Kevin Green (Supervisor) & Martin O'Driscoll (Supervisor)