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.

This thesis presents for the first time a symmetrical, bilateral model of central pathways in the vestibulo-ocular reflex (VOR), based on known neural pathways and their interconnections on both sides of the brainstem. The model explains, simultaneously, the known behaviour of individual neural groups within the system (in central pathways) and of eye movements at its output. It does not require a long time constant "neural integrator" (NI) nor separate pathways for the generation of slow and fast phases of nystagmus, as in previous models. A single "neural filter" (NF, time constant < 1s) on each side of the brainstem is sufficient to provide integration in the slow phase mode, with the help of a positive feedback loop due to commissural innervation. Fast/slow phase alternation of eye movements is achieved through simple modulation of commissural inhibition by reticular burst cells. / Analytic and computer simulation studies show that the model can account, for the first time, for published response characteristics in the vestibular nuclei, and for their dependence on commissural and cerebellar pathways.

Damage to one vestibular apparatus (unilateral vestibular deafferentation, UVD) results in severe postural and ocular motor disturbances (such as spontaneous nystagmus, SN) that recover over time in a process known as vestibular compensation. However, the underlying neurochemical mechanisms of vestibular compensation are poorly understood. While UVD affects many areas in the CNS, attention has focused upon the partially deafferented second order neurons in the vestibular nuclei complex (VNC). Several converging lines of evidence suggest that Ca�⁺-permeable ion channels (N-methyl-D-aspartate receptors and L-type voltage-gated Ca�⁺-channels) and intracellular Ca�⁺-dependent protein kinases play an important role in vestibular compensation. However, the nature of this involvement and the locus of these changes are unknown. The aim of this thesis was to investigate the role of Ca�⁺ signalling pathways in the VNC during vestibular compensation in guinea pig. These issues were investigated in three separate experiments that utilised two methodological approaches: i) in vitro assays were used to determine the nature and extent of protein phosphorylation within the VNC at various stages of compensation; and ii) ion channel blockers or cell-permeable kinase inhibitors were injected directly into the VNC immediately before UVD to determine whether or not these systems were causally involved in compensation. The results of experiment 1 (Chapter 5) showed that a bolus intra-VNC injection of an uncompetitive NMDA receptor antagonist, but not an L-type voltage-gated Ca�⁺ channel antagonist, temporarily reduced SN frequency at the earliest measurement time (6 hours post-UVD). These results suggested that the initial expression of SN required, in part, the activation of NMDA receptors in the VNC on the side of the UVD, and by inference, Ca�⁺ entry through the ion channel. The results of experiment 2 (Chapter 6) revealed that the medial VNC contains abundant Ca�⁺/calmodulin-dependent and Ca�⁺/phospholipid-dependent protein kinase activities. The same VNC tissue removed from animals at various times after UVD, showed that vestibular compensation is accompanied by specific changes in the phosphorylation of several major protein kinase C substrates. These included an unidentified 46-kDa band, and a 75-kDa band with similar characteristics to the myristoylated alanine-rich C kinase substrate (MARCKS). These results suggest that protein kinase C signalling pathways may be involved in vestibular compensation. The results of experiment 3 (Chapter 7) are consistent with these results showing that intra-VNC infusion of a protein kinase C inhibitor, but not a Ca�⁺/calmodulin-dependent protein kinase II inhibitor, significantly increased SN at the earliest measurement times (6 and 8 hours), but had no effect upon the time taken to achieve compensation or on postural compensation. These results suggest that the induction of SN compensation involves protein kinase C activity in the VNC. Taken together, these findings suggest that the mechanisms underlying the expression of SN (e.g., Ca�⁺ influx via NMDA receptors) are possibly distinct from those that initiate its compensation (e.g., PKC activation). The downstream effects of raised intracellular Ca�⁺ may involve protein kinase C-dependent phosphorylation of key intracellular proteins that initiate long-lasting changes in cellular function within the VNC.

Vertigo is the presenting symptom of some peripheral vestibular disorders, like Benign Positional Vertigo (BPV), Ménière's disease, and vestibular neuritis, and for many other clinical conditions as well. Some clinicians from the Christchurch Public Hospital suspect that there is a significant need to improve the diagnostic accuracy and overall management of patients presenting with complaints of "acute vertigo or dizziness", especially BPV and Ménière's disease. The final diagnosis of many such patients treated for these conditions in the past has been suspected to be somewhat incomplete or inappropriate. These patients were commonly referred to various other departments, where they underwent a number of investigations, particularly medical imaging [head CT (Computed Tomography) / MRI (Magnetic Resonance Imaging) scans, which were in many cases not necessary. Such delays in the process led to an extra or unnecessary burden on the limited health funds available to the hospital or to the patient. Another drawback was an elevated patient stress and anxiety as critical time was lost with the increased number of admissions, or in transferring the patient between various departments without any conclusive diagnosis and treatment. It was proposed to conduct a retrospective study on the accuracy of diagnosis of those patients admitted to Christchurch Public Hospital with complaints of acute vertigo, particularly for suspected peripheral vestibular disorders (mainly BPV and Ménière's disease) over the period of 2004-2005. Implementation of a more specific and detailed management approach at the level of the initial clinical examination or diagnostic investigations (specifically, by an early Otolaryngology/Audiology intervention) was planned for the year 2006. The two groups of patients (2004-2005 and 2006) were compared to verify the final achievements concerning the diagnostic accuracy and at various other levels with the newly implemented changes in 2006.

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.

Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 135-165).

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Thomas A. Houpt, Florida State University, College of Arts and Sciences, Dept. of Neuroscience. Title and description from dissertation home page (viewed June 12, 2006). Document formatted into pages; contains xiv, 112 pages. Includes bibliographical references.

Thesis (Ph.D.)--Ohio University, August, 2006. / Title from PDF t.p. Includes bibliographical references.

Orientador: Hari Mohan Gupta / Banca: José Roberto Campanha / Banca: Elbert Einstein Nehrer Macau / Resumo: Nesse trabalho analisamos a distribuição estatística das notas dos candidatos do vestibular da UNESP (Universidade Estadual Paulista) nos anos de 1998, 1999 e 2000, levando em conta o fato do aluno ter cursado o ensino médio no período diurno ou noturno, ter cursado em escola publica ou privada e possuir renda familiar até 10 salários mínimos ou superior a 10 salários mínimos. O vestibular é dividido em três áreas: Ciências Exatas, Ciências Biológicas e Ciências Humanas. Para cada área o candidato realiza três avaliações: conhecimentos específicos, conhecimentos gerais e língua portuguesa. O enfoque desse estudo é a avaliação de conhecimentos específicos das três áreas. Comparamos as distribuições das notas dos alunos que cursaram o ensino médio no período diurno e noturno, em escola publica e privada e com renda até 10 salários mínimos e superior a 10 salários mínimos, observamos a presença da distribuição de lei de potência gradualmente truncada e da distribuição normal como observado em vários sistemas naturais complexos. Finalmente discutimos e justificamos os resultados obtidos dessas distribuições. / Abstract: We studied the statistical distribution of studentþs performance, which is measured through their marks, in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) with respect to (i) period of study -day vs. night period (ii) teaching conditions - private vs. public school (iii) economical conditions - high vs. low family income. We observed long ubiquitous power law tails in Physical an Biological sciences in all cases. The mean value increases with better study conditions followed by better teaching and economical conditions. In humanities, the distribution is close to normal distribution with very small tail. This indicate that these power law tail in science subjects are due to the nature of the subject itself. Further better study, teaching and economical conditions are more important for physical and biological science in comparison to humanities at this level of study. We explain these statistical distributions through Gradually Truncated Power Law Distributions. We discuss the possible reason for this peculiar behaviour. / Mestre

Em um contexto de disputa por uma vaga no Ensino Superior, diversos projetos têm surgido para auxiliar estudantes de baixa renda na preparação para os concorridos exames. Denominamos esses espaços como Cursinhos Populares (CPs), projetos que propõem uma Educação Popular que visa a superação solidária e coletiva das barreiras que impedem a entrada de estudantes de baixa renda nas universidades. Esta pesquisa investiga a proposta pedagógica e o trabalho dos professores de Geografia de três CPs de Porto Alegre, e analisa o desempenho dos estudantes nos exames. O objetivo principal deste trabalho é investigar e analisar as estratégias desenvolvidas por professores de Geografia dos CPs no que diz respeito às metodologias de ensino adotadas. / En un contexto de disputa por una vacante en la Enseñanza Superior, diversos proyectos han surgido para auxiliar a estudiantes de baja renta en la preparación para los concurridos exámenes. Denominamos esos espacios como Cursinhos Populares (CPs), proyectos que proponen una Educación Popular que busca la superación solidaria y colectiva de las barreras que impiden la entrada de estudiantes de baja renta en las universidades. Esta tesis investiga la propuesta pedagógica y el trabajo de los profesores de Geografía de tres CPs de Porto Alegre, y analiza el desempeño de los estudiantes en los exámenes. El objetivo principal de este trabajo es investigar y analizar las estrategias promovidas por profesores de Geografía de los CPs en lo que se refiere a las metodologías de enseñanza adoptadas.