Hearing loss is a disability that affects thousands of people in the world. It is estimated that there is 400,000 people with hearing difficulties in New Zealand (New Zealand Audiological Society, 2007). People with hearing loss have the right to access to information and communication (United Nations Enable, 2003). Without access to information and communication, the hearing impaired may encounter problems with emotional and social functioning, and consequently suffer with decreased quality of life. Clinical experience and investigations have revealed success with assistive listening devices (ALDs) where use of hearing aids has been unsuccessful. ALDs are devices that improve the communication function for the hearing impaired. ALDs can be used with or without hearing aids to overcome the negative effects of poor room acoustics. Currently, in the literature, little is known about the use and maintenance of ALDs in community organizations. This study investigates the use and maintenance of ALDs in the Christchurch community of New Zealand. A list of community organizations that provide ALDs to the public of Christchurch was also made available to individuals who have hearing impairment. The study found there is a lack of ALDs within the Christchurch community. Also that current ALD technology within the Christchurch community is not necessarily compatible with current hearing aid technology and that most organizations rely too heavily on PA systems. PA systems do not necessarily meet the needs of the hearing impaired and an ALD specifically targeting their hearing loss would improve their speech perception. Community organizations are not advertising enough that they offer ALDs which adds to the lack of awareness in Christchurch. Results found that most ALDs in the Christchurch community are in working order, however, there is a need for organizations to be educated about their use and maintenance. Audiologists and other health professionals have a key role in providing appropriate recommendations in the use and benefits that ALDs have on speech perception. These will directly improve the listening situations that the hearing impaired have throughout their communities, thus improving their quality of life.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Diss. Linköping : Univ., 2003.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 4 uppsatser.

Thesis (doctoral)--Rijksuniversiteit te Groningen.

One of the most common disabilities in the US, hearing loss, is reported by The National Institutes of Health to affect approximately 36 million Americans. One of the major contributing factors to this loss in hearing is the loss of the sensory hair cells (HCs) within the cochlea. Also in the mammalian cochlea, six major groups of supporting cell (SC) subtypes reside in close proximity to HCs and may have the potential to regenerate HCs after damage. These subtypes include cells of the greater epithelial ridge, inner phalangeal/border cells, inner and outer pillar cells, Deiters’ cells, Hensen cells, and Claudius cells. During embryonic development, progenitor cells differentiate into HCs or one of the SC subtypes by Notch-mediated lateral inhibition. In the neonatal mouse cochlea, many studies have shown that inhibition of Notch signaling allows SCs to convert into HCs in both normal undamaged cochleae, as well as in drug-damaged cochlear explants. This mechanism is also implicated during spontaneous HC regeneration that occurs in non-mammalian vertebrates. We and others have recently observed that spontaneous HC regeneration can also occur in the neonatal mouse cochlea. However, little is known about the molecular mechanism or the SC subtypes which act as the source of regenerated HCs. In the neonatal mouse cochlea, HCs were killed in vivo at birth using a genetically-modified mouse model to express a toxin in HCs. Subsequently, SCs formed new HCs by either direct transdifferentiation, where no cell division occurred, or by mitotic regeneration. My dissertation investigated the role of Notch signaling in the ability of SC subtypes to regenerate HCs after damage. My central hypothesis is that after HC ablation is induced at birth, Notch signaling is partially eliminated and therefore lateral inhibition is lost in neonatal SCs in a subtype specific manner, which allows some SCs, but not others, to differentiate into and regenerate HCs. Aim 1 focused on changes in the Notch signaling pathway in response to HC damage during the window of spontaneous HC regeneration. Changes in the expression of genes in the Notch pathway were measured using real time qPCR, immunostaining, and in situ hybridization. The Notch effector HeyL was increased in the apical one-third of the cochlea while other Notch players are decreased. The most notable example is the Notch effector Hes5, which is directly responsible for inhibiting HC fate, and was reduced in outer pillar cells and Deiters’ cells, but not in other SC subtypes. From this we conclude that Notch signaling is reduced differentially among SC subtypes. In Aim 2 we investigated whether inhibition of Notch signaling is required for spontaneous HC regeneration to occur by maintaining active Notch signaling in all SCs in the context of HC damage. We hypothesized that maintaining active Notch signaling after HC damage will prevent SC-to-HC conversion thus preventing HC regeneration. We found significantly fewer regenerated HCs while maintaining Notch expression compared to controls with HC damage and no manipulation of Notch signaling. Therefore we conclude loss of Notch mediated lateral inhibition is required for the majority of spontaneous HC regeneration. In Aim 3 we investigated the ability of different SC subtypes to regenerate HCs by fate-mapping SC subtypes during the HC regeneration process. Since fate-mapping creates a permanent label in targeted cells, we can track their potential change in cell fate or reentry in the cell cycle after HC damage. We hypothesized that pillar cells and Deiters’ cells are the source for spontaneously regenerated HC within the neonatal mouse cochlea based on our results from Aim 1. We used three CreER mouse lines to fate-map distinct groups of SC subtypes during the HC damage and regeneration process. More pillar and Deiters’ cells regenerated HCs after damage than other SC populations. We found that outer pillar cells and Deiters’ cells are capable of downregulating the cell cycle inhibitor, p27Kip1, after HC damage. Therefore we investigated the ability of SC subtypes to mitotically regenerate HCs by including a mitotic tracer along with fate-mapping. A larger proportion of mitotically regenerated HCs came from pillar and Deiters’ cells. From these experiments, we conclude that outer pillar and Deiters’ cells are the source for the majority of spontaneously regenerated HCs in vivo. This knowledge will allow targeted investigation into outer pillar cells and Deiters’ cells that maintain regenerative plasticity at postnatal ages. Understanding how these cells change with age will inform efforts to induce HC regeneration in more mature cochleae. Additionally, understanding how Notch signaling regulates this regenerative plasticity will lead to the development of potential targets for the treatment of hearing loss.

Abstract This study was undertaken to improve the diagnosis of otitis media and to investigate possible hearing loss caused by middle ear effusion (MEE) in small children. The accuracy of minitympanometry in detecting MEE was evaluated in 162 children. The finding was compared with the amount of effusion found in myringotomy. Minitympanometry proved to be an accurate method to detect MEE in young children, the sensitivity and specificity values being 79% and 93% in cooperative children but it had no value in non-cooperative children. Minitympanometric examination could be performed successfully with good cooperation in 87% of a total of 206 children in paediatric outpatient clinic. Impaired mobility of the tympanic membrane (TM) was the best sign of MEE in pneumatic otoscopy of 76 children, with sensitivity and specificity values of 75% and 90%, respectively. The influence of nitrous oxide (N2O) on MEE was tested by weighting the effusion found in myringotomy during general anaesthesia with and without N2O in 39 and 37 children, respectively. The mean weight of the effusion in the oxygen-air group did not differ from the weight in the N2O group, and thus peroperative findings in myringotomy are reliable. Studies on symptomatology and the temporal development of acute otitis media (AOM) during upper respiratory tract infection (URI) were based on three-month follow-up of 857 children. Symptoms of URI only were compared with symptoms of URI complicated by AOM in the same child in 138 children. The most important symptom associated with AOM was earache, with a relative risk of 21.3. Sore throat, night restlessness and fever at days 3-6 were also significantly associated with AOM, with relative risks of 3.2, 2.6 and 1.8, respectively. In 44 children under two years of age, earache, conjunctival symptoms and cloudy rhinitis were significantly associated with AOM. Temporal development of AOM was assessed from 250 episodes in 184 children. Sixty-three per cent of cases of AOM occurred during the first week after the onset of URI, peaking on days 2 to 5. The onset of AOM in children with a history of recurrent episodes of AOM did not differ from that in those who had experienced only a few episodes of AOM. No individual tendency was noticed among children suffering more than one AOM episode during follow-up. To assess the influence of the quantity and quality of MEE on hearing in small children, transient evoked otoacoustic emission (TEOAE) was performed under general anaesthesia before myringotomy in 185 ears of 102 children. Reduced TEOAEs indicating hearing loss were found in 83% of the ears with mucoid effusion and in 56% of the ears with non-mucoid effusion, the difference being statistically significant (p < 0.01). A significant negative correlation between the reproducibility of TEOAE responses and the amount of effusion was found (Spearman rank correlation coefficient r = -0.589, p < 0.001). Findings in minitympanometry correlated with the responses of TEOAE. Although parents are able to predict AOM quite reliably, various symptoms and the duration of URI seems to be of little value in helping the diagnosis of AOM. Detection of effusion in OM may be improven by minitympanometry in cooperative children. Any kind of effusion may cause hearing loss in small children, which must be considered when treating OM.

Noise exposure is one of the most common hazards in the work force. There are multiple occupations that experience large amounts of noise exposure to its employees on a regular basis. Flight ground crews and flight maintenance personnel are among the nosiest jobs that exist. Despite the mandatory hearing protection requirements for a job of this caliber, there still remains a chance of an over exposure to noise. Most of the exposure comes from the different types of loud repair equipment and tools, but the greatest exposure comes from a jet engine that can reach 140 decibels. Flight maintenance personnel often work in an environment where the hours are long and there is continuous noise at high decibels. Flight maintenance personnel are typically in multiple places throughout a workday because of the maintenance responsibilities of different equipment, trucks, and planes. This study will examine the noise exposure levels of the service members in the Aerospace Ground Equipment (AGE) department on a United States Air Force base. The study will help determine if the service members in the AGE department are being over exposed to noise from their daily routines as flight repair personnel. There has been previous noise sampling done on the AGE department and there will be a comparison of data due to different equipment, change in personnel, and standard operating procedures for the department. The bioengineering/ environmental department is typically responsible for sampling of the AGE department. They have had a difficult time with suggesting engineering controls due to the constant mobility of the maintenance crews. As a result, they have to rely heavily on administrative controls and effective Personal Protective Equipment (PPE). This study will include sampling for a standard workday including day and night shift for the AGE department. The sampling will be done by using personal noise dosimeters and a sound level meter will be used to conduct area sampling for equipment in AGE shop. The AGE department on the Air Force base agreed to allow personnel from their shop to participate in this study. In this study, we will adhere to the Air force safety regulations and sampling techniques

Multitasking in background noise may involve greater cognitive processing demands than multitasking in quiet due to an increase in perceptual demands (Rabbitt, 1968; Pichora-Fuller & Schneider, 2000). This study investigated the effect of background noise in the listening environment on the ability of young adults with normal hearing and older adults with sensorineural hearing loss to perceive speech while performing a secondary task. A dual task paradigm, which included word recognition and visual serial recall, was used to examine ability to divide limited processing resources between two tasks. The number of digits to be recalled was varied in order to test the hypothesis that background noise would degrade multitasking abilities to a greater degree than in quiet for more difficult tasks. Participants included 37 native English speakers between 19-25 years of age with pure-tone thresholds better than or equal to 20 dB HL and 10 English speakers between 58-85 years of age with pure-tone thresholds greater than or equal to 25 dB HL in both ears. The results showed that background noise can have negative effects on the ability to multitask for both younger adults with normal hearing and older adults with hearing loss; however, this effect was greater for the older adults with hearing loss, especially when task demands were increased.

Dissertation (MCommunication Pathology)--University of Pretoria, 2013. / Speech-Language Pathology and Audiology / Unrestricted