Thesis ( M Med (Anaesthesiology)--University of Limpopo, 2011. / Introduction: Multiple studies have described a variable incidence of transient hearing loss (hypoacousis) from 0.4% to 40% after subarachnoid block, especially in the low-frequencies range (125 – 500 Hz) (1, 2). The mechanism of transient hypoacousis is attributed to leakage of cerebrospinal fluid, which leads to a decrease in perilymph pressure within the cochlear. Hypothesis: The study hypothesis was based on an assumption that hearing loss is more frequent in young patients who undergo spinal anaesthesia in comparison with elderly patients. Objective: 1) To determine the incidence of hearing loss after spinal anaesthesia in the young versus elderly patients. Materials and Methods: Ninety-eight male patients (ASA 1 - 11) scheduled for cystoscopy under spinal anaesthesia were recruited for the study. Recruitment of patients for the study was age-dependent and was divided into two groups: One group (49 patients) had patients aged between 17 and 44 years (Group Y) and the other group had 49 patients aged between 45 and 77 years made up group two (GROUP E). Subarachnoid injection at L3-4 was performed using a standard 22-gauge Quincke spinal needle with patients in the sitting position and 2,5 ml to 3 ml of 0.5% isobaric bupivacaine was administered. Patients were evaluated on the day before spinal anaesthesia by pure tone audiometry at three different frequency sounds viz. 125 – 500 Hz (Low frequency), 500 – 2000 Hz (Speech frequency) and at 2000 – 4000 Hz (High frequency). This assessment was repeated 48 hours after the spinal block was given. Statistical Analysis: Analysis was descriptive providing information on the mean (or median) and standard deviation of the variables for each of the two groups. The results of the audiometry were analyzed using repeated measures analysis of variance and transformation to p-value. Differences in outcomes of the study between the two groups were recorded as being statistically significant if p-value is ≤ 0.05. Results: No patient from the two groups developed hearing loss either at low or high frequencies. However, there was a statistically significant improvement in audiometric results (p-value ranging from 0.0001 and 0.063) 48 hours post-surgery in the elderly group as compared with patients in the younger group. Conclusion: The study revealed no hearing loss post-spinal anaesthesia in both groups. It did, however, show that the elderly group have better hearing acuity at all three frequency levels of sound compared to the younger group after spinal anaesthesia.

Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2031-01-01

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The decision regarding cochlear implantation is complex and involves the consideration of a multitude of factors that will influence the future of a hearing impaired child. Parents are often faced with the task of making this decision urgently during a period when they dealing with the diagnosis of a hearing loss. To date, there is sparse literature available on parental readiness for cochlear implantation. An understanding of parental experiences during the decision making process will help professionals involved in the cochlear implant teams to help parents through this difficult decision making time and hence have significant clinical implications for future practice. This is particularly relevant in South Africa where there is very little literature to guide both parents and professionals with regard to decision making. The objective of this study was to determine parental descriptions of their experiences with regard to the decision of cochlear implantation for their young children with hearing loss as well as the factors that needed to be considered by the parents for the child when deciding on a cochlear implant. Semi structured interviews were conducted with 13 parents at a Learning Facility in South Africa. The results revealed that the decision for cochlear implantation was based on two critical factors which were the sense of urgency and the future of the child. Other considerations such as the financial consideration, surgical risk, aesthetics, communicative outcomes, family consensus, and parental readiness were identified. The power of professionals during this time when decisions are being made in the context of ignorance and within an oral environment was revealed. This finding raised the question of the ethical and moral practice of professionals involved in cochlear implantation.

Otosclerosis is a common form of adult-onset hearing loss. It is a complex disease that most likely involves multiple genetic and environmental factors. We know that a genetic component for otosclerosis exists because of the overwhelming ethnic bias and the fact that nearly half of patients report a family history. Many family linkage studies and candidate gene association studies have been performed; however, disease-causing mutations remain elusive. The disease is caused by abnormal bone remodeling in the otic capsule, which normally undergoes very little remodeling after development and ossification. This is in stark contrast to the rest of the skeleton, which undergoes bone turn over at a rate of nearly 10% per year. How the otic capsule remains in such a static state is under investigation, but initial studies suggest that bone remodeling inhibitors produced by the inner ear are responsible. In patients with otosclerosis it is uncertain what events trigger this abnormal bone remodeling. To determine its cause, many environmental and genetic factors have been entertained. However, even with decades of research on the disease, we still know little about its etiology. My thesis work has aimed to identify molecular and genetic contributors to the disease. To do this, I have performed a global gene expression analysis of otosclerotic tissue to determine what genes are differentially expressed in the disease compared to control tissue. This study has identified a number of differentially expressed genes and pathways potentially involved in the disease. To compliment this work, I also performed a genome-wide association study, in collaboration with a group from Belgium. Together we identified an unexpected gene, RELN, as being associated with otosclerosis in six different European populations. This marks the first successful genome-wide association study for a hearing impairment. I have also identified rare variants in several candidate genes in the TGF-â superfamily in otosclerosis patients. Further analysis of these variants has identified a few that appear to alter protein function, giving us a glimpse of what they may be doing to cause disease. While we still cannot account for most of the heritability for otosclerosis, we have come a long way in identifying new candidates, in which future analysis will hopefully lead to a better understanding of the disease. In the long term, I hope this work will help provide better treatment options for patients with this disease.

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Following vestibular schwannoma excision, a subset of cases has been reported in which hearing is present immediately after surgery, but is lost in the early postoperative period. Such cases have rarely been reported, and the postoperative audiological data collected from patients in these cases lacks the time resolution necessary to determine the pathophysiological mechanism responsible for the pattern of hearing loss. The present study aimed to more clearly define delayed hearing loss by collecting detailed data documenting changes in behavioural and electrophysiological auditory responses following vestibular schwannoma surgery. In particular, we aimed to use this data to determine the time course of changes in auditory function and to identify whether the site of impairment was cochlear or neural. Preoperative and daily postoperative monitoring of auditory function was performed in 19 patients undergoing vestibular schwannoma excision via the retrosigmoid approach at Christchurch Public Hospital. The pre- and postoperative assessment battery included pure-tone and speech audiometry, tympanometry, tone decay, distortion product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR) measurement. Intraoperative ABR was performed in four cases in which clear preoperative waveforms were present. Transtympanic electrocochleography (ECochG) was carried out if wave I was lost in the early postoperative period. Thirteen of the 19 patients suffered immediate anacusis following surgery and six had measurable hearing postoperatively. The behavioural and electrophysiological data collected in each case is discussed with regard to the likely pathophysiology of pre- and postoperative hearing loss. No patients demonstrated behavioural evidence of delayed hearing loss, however a gradual deterioration of ABR in the early postoperative period was observed in Case 16. ECochG and DPOAEs in this case indicated the presence of cochlear function although the patient presented with immediate postoperative anacusis in the ipsilateral ear. These results are consistent with postoperative retrograde degeneration of the cochlear nerve.