MRI Mensuration of the Canine Head: the Effect of Head Conformation on the Shape and Dimensions of the Facial and Cranial Regions and Their Components
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Hussein, Aseel Kamil (2012) MRI mensuration of the canine head: the effect of head conformation on the shape and dimensions of the facial and cranial regions and their components. PhD thesis http://theses.gla.ac.uk/3689/ Copyright and moral rights for this thesis are retained by the author A copy can be downloaded for personal non-commercial research or study, without prior permission or charge This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the Author The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the Author When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given. Glasgow Theses Service http://theses.gla.ac.uk/ [email protected] MRI Mensuration of the Canine Head: the Effect of Head Conformation on the Shape and Dimensions of the Facial and Cranial Regions and Their Components Aseel Kamil Hussein BVMS, MSc Submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy University of Glasgow School of Veterinary Medicine June, 2012 © Aseel K. Hussein 2012 Declaration I declare that the work recorded here is solely mine, except where otherwise stated. Aseel The thesis is approved by the supervisors, Professor Jacques Penderis and Professor Martin Sullivan, at School of Veterinary Medicine, College of Medical Veterinary & Life Sciences. Jacques Penderis Martin Sullivan Summary The selection for specific physical characteristics by dog breeders has resulted in the expression of undesirable phenotypes, either directly or indirectly related to the physical characteristic selected for. One conformation that was considered desirable is extreme brachycephalia, which is associated with secondary physical changes adversely affecting the airways, eyes and central nervous system. Using a large population of pet dogs having diagnostic magnetic resonance imaging (MRI) studies, I demonstrated that the most commonly used historical head phenotype indices (Stockard and Evans indices) can be determined on MR images. I furthermore conformed that olfactory bulb angulation can be used as an alternate for classification of dog into brachycephalic, mesaticephalic and dolichocephalic head shapes, with similar results to the historical indices. The advantages of olfactory bulb angulation are that it only requires a single midline MR image and inclusion of the entire nose is not required. Using the historical indices and olfactory bulb angulation I then examined the effect of increasing brachycephalia on the appearance and dimensions of the nasal and cranial cavity. I established that progressive ventral rotation of the olfactory bulb (increasing brachycephalia) resulted in an alteration in the shape and a reduction in cross-sectional area of the nasopharynx. Similarly, increasing brachycephalia resulted in a reduction in the dorsal area of the ethmoturbinates and a corresponding reduction in the midline area of the olfactory bulb, providing a potential explanation for reduced olfactory acuity in brachycephalic dogs. Finally, I examined the effect of head phenotype on the structures of the middle fossa, the 3rd ventricle, quadrigeminal cistern and interthalamic adhesion. Head phenotype had a lesser effect on these structures, while brain disease (in particular ventriculomegaly) has a substantial effect, the recognition of which I described. These results confirm the potential of olfactory bulb angulation and orientation for objectively determining head phenotype using in vivo MRI, in particular determining the degree of brachycephalia. The study also quantified the effect of brachycephalia on the nasal cavity and rostral and middle cranial fossae dimensions. The objective quantification of head phenotype provides a useful tool for selection of breeding animals to normalise extreme brachycephalia. This might reduce the incidence of the adverse effects associated with extreme brachycephalia. ii Table of Contents Declaration………………….………………………………………………………….…i Summary ............................................................................................................ ii Dedication .......................................................................................................... iv Acknowledgements ............................................................................................. v List of Chapters .................................................................................................. vi List of Tables...................................................................................................... xi List of Figures ................................................................................................... xv iii Dedication To anyone who has, does or will give some attention to animals, orphans and elderly people. Aseel iv Acknowledgements After thanking The God “Allah the almighty” for giving me such strength to pass all the difficulties during my PhD, I am extremely grateful to my supervisors: Professors Jacques Penderis and Martin Sullivan for providing me with great discussions, comments on manuscripts and help with developing ideas. In particular for the huge support and patience they gave me to produce this thesis. So I want to tell you that I indeed believe without you, I would not be able to achieve half of this work, so thanks from all of my heart. I am also very indebted to Professor Tomas F. Fletcher [DVM, PhD, College of Veterinary Medicine, University of Minnesota, USA] for being willing unflaggingly to engage in intellectual dialogue that supported, and gave me confidence in, my opinions in the early stages of the project. Dr. Tim Parkin [BSc, BVSc, PhD, DipECVPH, FHEA, MRCVS, School of Veterinary Medicine, University of Glasgow, UK] who provided valuable statistical advice throughout the study. I am also appreciative to Professor Gheorghe M. Constantinescu [DVM, PhD, College of Veterinary Medicine, University of Missouri-Columbia] and Professor Jack Boyd, Emeritus Professor of Clinical Anatomy, for clarifying points I needed within my work. My thanks also go to the Diagnostic Imaging Unit staff for their assistance. In addition, I would like to give thanks to Dr. Julia Edgar, Mr. Richard Irvine and Mr. Iain McNaught, and all those whose names are not mentioned here, for their direct or indirect assistance. I extend my deepest gratitude and appreciation to all of the above Last, but by no means least, I must also give my thanks to my sponsor, the Iraqi Higher Ministry, which funded my studies, which has allowed me to develop my career for the future. Aseel v List of Chapters 1 GENERAL INTRODUCTION .................................................................................. 1 1.1 An introduction to the clinical significance of head phenotype .......................... 2 1.2 Gross features of the skull ................................................................................... 4 1.2.1 Facial region .................................................................................................... 5 1.2.2 Palatal region ................................................................................................... 7 1.2.3 Neural region and the related brain components............................................. 9 1.3 The ventricular system of the brain ................................................................... 12 1.4 Methods of diagnostic imaging of the canine head ........................................... 15 1.5 Terminological inexactitude.............................................................................. 17 1.6 Skull indices ...................................................................................................... 19 1.6.1 Classification of dogs according to the skull shape ...................................... 20 1.7 Aim of the current work .................................................................................... 22 2 GENERAL MATERIALS & METHODS ............................................................... 23 2.1 Introduction ....................................................................................................... 24 2.2 Animals ............................................................................................................. 24 2.3 Magnetic Resonance Imaging ........................................................................... 24 2.3.1 T1 sequence ................................................................................................... 25 2.3.2 T1 sequence with contrast ............................................................................. 25 2.3.3 T2 sequence ................................................................................................... 25 2.3.4 Sagittal plane ................................................................................................. 26 2.3.5 Transverse plane............................................................................................ 26 2.3.6 Dorsal plane .................................................................................................. 26 2.4 Software ............................................................................................................ 26 2.4.1 Image Storage................................................................................................ 26 vi TM 2.5 eFilm Workstation 3.0 ..................................................................................