In retrospektiv angelegten Untersuchungen soll der Einfluss unterschiedlicher Operationsstrategien auf die Morbidität bei der Behandlung des Akustikusneurinoms aufgezeigt werden. In einer ersten Untersuchung wurde der Einfluss eines doppelten Verschlusses der Dura mater nach subokzipitaler Kraniotomie zur mikrochirurgischen Exstirpation eines Akustikusneurinoms im Hinblick auf die Vermeidung einer Liquorfistel analysiert. Hier wurden zwei Patientengruppen miteinander verglichen. Zum einen Patienten mit einem einfachen Duraverschluss, Duranaht plus alloplastisches Material epidural. Zum anderen Patienten mit einem doppelten Duraverschluss. Hier epidurales und subdurales alloplastisches Material plus Duranaht. Untersucht wurden das Auftreten von Liquorfisteln sowie die Häufigkeit von Wundheilungsstörungen. Es konnte keine signifikante Überlegenheit einer Operationstechnik zur Vermeidung von postoperativen Liquorfisteln gezeigt werden. In einer zweiten Untersuchung wurde der Zusammenhang einer inkompletten Resektion des Tumors (Belassen eines Kapselrestes) mit dem Ziel der Schonung des Nervus facialis untersucht. Hierzu wurden die postoperative Facialisfunktion sowie ein möglicherweise erhöhtes Rezidivrisiko im Verlauf betrachtet. Die postoperative Funktion des N. facialis wurde zwischen den Patientengruppen mit Kapselrest (inkomplette Entfernung) und ohne Kapselrest (komplette Entfernung) verglichen. Es zeigte sich bei vergleichbarer postoperativer Facialisfunktion kein signifikanter Unterschied im Auftreten von Rezidiven nach inkompletter Resektion. Nur gut ein Drittel der inkomplett resezierten Tumore zeigten im Nachbeobachtungszeitraum (im Mittel 52 Monate) überhaupt ein Wachstum.

Thesis--M. Phil., University of Hong Kong. / Mimeographed.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Master / Master of Philosophy

Psychiatric disorders and cognitive impairment are increasingly being described in patients with vestibular pathology. Yet frameworks that describe the link between emotion, memory and the vestibular system have yet to reach maturity, partly because studies have not yet provided detailed accounts of behavioral changes in experimental animals, or in man. One of the goals of this thesis was to use experimental psychology to define changes in memory and emotional behaviour in rats given bilateral vestibular deafferentation (BVD, n=18) or sham surgery (Sham, n=17). In an elevated-plus maze task, BVD rats made up to 166% greater open arm entries and spent up to 42% more time in the open arms compared to Sham rats. In an elevated-T maze task, BVD rats failed to develop a normal learned inhibition response to open space. In an open field maze BVD rats consistently showed 50-60% greater movement velocity, spent on average 35% more time in the inner most aversive part of the arena, and failed to show the normal boundary-seeking behaviour (thigmotaxis) typical of untreated or Sham rats. In a social interaction test BVD rats spent up to 34% less time engaged in social contact compared to Sham rats. In a hyponeophagia test, BVD rats� latency to eat was 70% greater than Sham rats at 3-weeks post-op., however this difference disappeared at 3- and 5-months. These findings suggest that BVD treatment may in some cases disrupt normal behavioral inhibition. Memory performance was also affected. In a T-maze task BVD rats achieved 40-60% correct arm entries, compared to 90-100% for Sham controls. In a foraging task carried out in darkness, BVD rats� initial homing angle was random, homing paths were ~70% longer, and reference memory errors were ~56% greater compared to Sham rats. To elucidate possible neurochemical substrates for these behavioral changes, western blot assays on monoamine proteins were carried out on tissue from a naïve set of rats (BVD n=6; Sham n=6). In BVD rats, serotonin transporter protein expression was 39% lower in CA1 hippocampus and 27% lower in the forebrain region, despite forebrain tryptophan hydroxylase expression being 34% upregulated. Tyrosine hydroxylase expression in the forebrain region was 27% lower in BVD rats. Proteins related to synaptogenesis were also investigated. In the dentate gyrus SNAP-25 was 37% upregulated in BVD rats, while in area CA2/3 of the hippocampus neurofilament-L was 13% upregulated. Forebrain and entorhinal cortex drebrin expression was 28% and 38% downregulated in BVD rats. Neurofilament-L was also 31% downregulated in the forebrain region of BVD rats. To test whether any of these behavioral or biochemical changes may have been attributable to chronic physiological stress, a corticosterone assay was carried out at the conclusion of behavioral testing; however, the no significant between treatment differences were found. In conclusion, vestibular information appears to be needed for the acquisition of spatial and reference memory as well as the normal expression of emotional behaviour. The neurochemical changes described herein point toward possible substrates for these behaviors, however their full significance has yet to be determined.

Thesis (M. Med. Sc.)--University of Hong Kong, 2007.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 108-131) Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 108-131) Also available online.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 185-218).