Post-implantation facial nerve stimulation is a common side-effect of cochlear electrical stimulation. Facial nerve stimulation can often be resolved through adjustments in speech processor fitting but, in some instances, exhibit limited benefit or may have a detrimental effect on speech perception. In this study, the apical reference stimulation mode was investigated as a potential intervention to facial nerve stimulation. Firstly, a model refinement software tool was developed to improve the accuracy of models created by an automated workflow. Secondly, the refined model of the human cochlea, facial nerve and electrode array, coupled with a neural model, was used to predict excitations of auditory and facial nerve fibres. Finally, psychoacoustic tests were used to determine auditory comfort and threshold levels for the apical reference stimulation mode while simultaneously capturing electromyography data. The refinement tool illustrated an improved accuracy compared to measured data. Models predicted a desirable outcome for apical reference stimulation, as facial nerve fibre thresholds were higher and auditory thresholds were lower, in direct comparison to conventional monopolar stimulation. Psychoacoustic tests illustrated decreased auditory thresholds and increased dynamic range during apical reference stimulation. Furthermore, apical reference stimulation resulted in lower electromyography energy levels, compared to conventional monopolar stimulation, which suggests a reduction in facial nerve stimulation. Subjective feedback corroborated that apical reference stimulation alleviated facial nerve stimulation. This suggests that apical reference stimulation may be a viable strategy to alleviate facial nerve stimulation considering the improvements in dynamic range and auditory thresholds, complemented with a reduction in facial nerve stimulation / Dissertation (MEng (Bioengineering))--University of Pretoria, 2019. / NRF / Electrical, Electronic and Computer Engineering / MEng (Bioengineering) / Unrestricted

The objective of this study was to describe the influence of tinnitus distress on quality of life (QoL) outcomes in adult cochlear implant (CI) recipients who experience tinnitus, and to investigate the prognostic significance of tinnitus distress over time. A retrospective, longitudinal study of 210 adult (_18 years) CI recipients implanted between 2001 and 2017 was conducted. Data on hearing-related QoL, using the Abbreviated Profile of Hearing Aid Benefit (APHAB) and tinnitus distress, using the Tinnitus Reaction Questionnaire (TRQ) were captured preoperatively as well as at 6-months, 12-months and >24-month postoperatively. The effect of tinnitus distress on hearing-related QoL outcomes over time was determined. Furthermore, 13 potential predictive factors were identified from the retrospective dataset, including demographic, hearing loss, CI, speech perception and tinnitus related factors. Multiple regression analyses were performed to identify variables that influence hearing-related QoL outcomes over time. Lower tinnitus distress and younger age at implantation were the only two out of 13 possible predictor variables that were identified as significant predictors of better hearing-related QoL in adult CI recipients. A general trend of statistically significant (p<0.01) tinnitus relief was evident from the preoperative interval to the 6-months, 12-months and >24-months postoperative intervals, confirming significant relief in tinnitus distress up to more than two years post-implantation. Within this dataset, higher levels of tinnitus distress were associated with poorer hearing-related QoL outcomes, as confirmed by the negative correlation between tinnitus distress and hearing-related QoL. This study contributes to a better understanding of the complex influence that multifactorial variables has upon the hearing-related QoL outcomes of adult CI recipients. This enables clinicians to provide evidence-based preoperative counselling combined with postoperative rehabilitation to adult CI recipients and their families. Not only was tinnitus distress confirmed as a predictive factor for hearing-related QoL in this study, but also the association between residual tinnitus distress and hearing-related QoL. These results emphasize the importance of identification, counselling and timely monitoring of adult CI recipients who experience tinnitus. / Dissertation (MA)--University of Pretoria, 2019. / Speech-Language Pathology and Audiology / MA / Unrestricted

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