1 Mechanisms of axonal dysfunction in facial nerve disorders Timothy James Eviston thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy Faculty of Medicine University of New South Wales 2016 PLEASE TYPE THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Eviston First name: Timothy Other name/s: James MDCN9001 Abbreviation for degree as given in the University calendar: School: Prince of wales clinical school Faculty: Medicine Title: Mechanisms of axonal dysfunction in facial nerve disorders Abstract 350 words maximum: (PLEASE TYPE) Facial palsy is a debilitating condition which has a dramatic impact on aesthetic appearance, quality of life and social interaction. Significant uncertainty still exists for clinicians around how to diagnose a cause, determine an accurate prognosis, when to time interventions and how best to optimise recovery. The underlying pathophysiology of nerve dysfunction and associated phenomena such as synkinesis (mass movement of muscle groups) and hypertonicity is also poorly understood. This thesis explores the development and application of new neurophysiology techniques to advance the understanding of how ion channel activity and functional axonal properties change in the context of disease states. These findings are then analysed in the context of recent advances in the understanding of axonal neurobiology and cell degeneration pathways to enable new perspectives on this important condition. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertationin whole or in partin the University libraries in all forms of media, now or here afterknown, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). Signature ·· , ....... The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and re uire the a roval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: ORIGINALITY STATEMENT 'I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.' Signed .............. Date 3)/1/!b COPYRIGHT STATEMENT 'I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or partof this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in DissertationAbstract International (this is applicable to doctoraltheses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/willapply for a partial restriction of the digital copy of my thesis or dissertation.' Signed Date AUTHENTICITY STATEMENT 'I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.' Signed - ·-·················· Date 241;z 2 Acknowledgments Four years ago I met Professor Arun Krishnan to discuss the possibility of pursuing a PhD under his supervision. My thinking at the time was that, as someone with a surgical background, I needed a supervisor with expertise in clinical neurology and neuroscience if I were going to successfully translate nerve injury expertise into the surgical context and contribute a new perspective to the treatment of facial nerve disorders into the future. My criteria for choosing a supervisor were that they have integrity, be world-class, and be patient focused. Professor Krishnan was the perfect supervisor. I was given freedom to explore, experiment and pursue my areas of interest while having the right amount of guidance to keep me heading in the right direction. Thank you Arun for your leadership, judgement, kindness and mentorship. To Natalie Kwai, Ria Arnold, Jenna Murray and William Huynh, thank you for welcoming me as one of the team. I felt at home from day one and I am constantly inspired by your devotion and passion for research. To Jonathan Clark, John McGuinness and Bruce Ashford, your mentorship over the years has inspired me to be a better person, to put patients and the community first, and to work hard to be a better surgeon. Glen Croxson, Sue Coulson, Lauren Chong and the Sydney Facial Nerve team, it has been a privilege working with you as we see our fledgling service grow. I am deeply thankful for your support and friendship and I hope many more PhD’s come out of our clinic in the future. I am eternally grateful to my patients and the volunteers who took part. The sacrifices you have made to be involved in this research endeavor are greatly appreciated. I am grateful to the National Health and Medical Research Council and to UNSW for supporting me while I undertake this research endeavor. To my family and friends, thank you for your enduring support. Finally, to my wife, Grace, thank you for your love, patience and support. This PhD was made possible because of you. 3 Abstract This thesis investigated the underlying physiology of the human facial nerve in health and disease. This involved the translation and optimisation of techniques for determining axonal excitability measures in the human facial nerve. The techniques have proven to be valuable in determining pathophysiology in neuropathies and it was hypothesised that the information they provide may be helpful in understanding facial nerv disorders. The initial studies developed the technique in healthy controls and established normative data (Chapter 1). The initial study in a disease grou (Chapter 2) was targeted at a broad cross-section of facial palsy patients to explore the utility of the technique. Findings consistent with membrane hyperpolarisation were demonstrated. Subsequent studies examined specific disease groups including Bell’s palsy (Chapter 3), facial synkinesis (Chapter 4), and assessment of facial nerve function of the contralateral face to facial palsy (Chapter 5). Changes consistent with reduced inward sodium conductances were noted in Bell’s palsy and these occurred in a pattern that has been noted with tetrodotoxin ingestion. In patients with facial synkinesis, changes in excitability were observed that would be consistent with axonal membrane depolarisation and which may predispose to ectopic motor activity. Altered facial nerve function was also noted in recordings from the contralateral face in patients who had experienced facial palsy and the pattern of change varied accordin to the severity of facial palsy. These changes provide physiological support for treatment of the contralateral face with chemodenervation in patients with facial palsy. 4 Table of Contents Acknowledgments 2 Abstract 3 Publications and presentations 5 Abbreviations 8 Literature review 9 Chapter 1: Assessment of axonal excitability properties in two branches of the human facial nerve 58 Chapter 2: Altered axonal excitability in chronic facial palsy 77 Chapter 3: Evidence of sodium channel dysfunction in Bell’s palsy 89 Chapter 4: Axonal dysfunction in facial synkinesis 108 Chapter 5: Axonal abnormalities in the contralateral face in the setting of facial palsy 120 Summary and Conclusions 135 References 138 5 Publications and presentations Articles submitted for review Chapter 2: Eviston TJ, Chong L, Clark JR, Krishnan AV. Altered axonal excitability properties i facial palsy. Muscle and Nerve, submitted August 29 2016 Chapter 3: Eviston TJ, Krishnan AV, Evidence of sodium channel dysfunction in Bell’s palsy, Brain, submitted August 27 2016 Chapter 4: Eviston TJ, Chong L, Clark JR, Krishnan AV. Axonal dysfunction in facial synkinesis. Movement Disorders, submitted August 31 Published works Literature review: Eviston TJ, Croxson GR, Kennedy PGE, Hadlock T, Krishnan AV. (2015). Bell's palsy: aetiology, clinical features and multidisciplinary care. Journal of Neurology, Neurosurgery, and Psychiatry, 86(12), 1356–1361. Chapter 1: Eviston TJ, Krishnan AV. (2016) Assessment of axonal excitability properties in two branches of the human facial nerve. Journal of Neuroscience Methods, 274, 53-60. Associated publications Eviston TJ, Yabe TE, Gupta R, Ebrahimi A, Clark JR. (2016). Parotidectomy: surgery in evolution. ANZ Journal of Surgery, 86(3), 193–199. 6 Pham M, Eviston TJ, and Clark JR. (2016), Reconstruction of limited parotidectomy defects using the dermofat graft. ANZ Journal of Surgery.