title: Craniometric Analysis of the Hindbrain and Craniocervical Junction of Chihuahua, Affenpinscher and Cavalier King Charles Spaniel Dogs With and Without Syringomyelia Secondary to Chiari-Like Malformation.
abstract: OBJECTIVE
  To characterize and compare the phenotypic variables of the hindbrain and craniocervical junction associated with syringomyelia (SM) in the Chihuahua, Affenpinscher and Cavalier King Charles Spaniel (CKCS).
  
  
  METHODS
  Analysis of 273 T1-weighted mid-sagittal DICOM sequences of the hindbrain and craniocervical junction from 99 Chihuahuas, 42 Affenpinschers and 132 CKCSs. The study compared 22 morphometric features (11 lines, eight angles and three ratios) of dogs with and without SM using refined techniques based on previous studies of the Griffon Bruxellois (GB) using Discriminant Function Analysis and ANOVA with post-hoc corrections.
  
  
  RESULTS
  The analysis identified 14/22 significant traits for SM in the three dog breeds, five of which were identical to those reported for the GB and suggest inclusion of a common aetiology. One ratio, caudal fossa height to the length of the skull base extended to an imaginary point of alignment between the atlas and supraoccipital bones, was common to all three breeds (p values 0.029 to <0.001). Associated with SM were a reduced occipital crest and two acute changes in angulation i) 'sphenoid flexure' at the spheno-occipital synchondrosis ii) 'cervical flexure' at the foramen magnum allied with medulla oblongata elevation. Comparing dogs with and without SM, each breed had a unique trait: Chihuahua had a smaller angle between the dens, atlas and basioccipital bone (p value < 0.001); Affenpinschers had a smaller distance from atlas to dens (p value 0.009); CKCS had a shorter distance between the spheno-occipital synchondrosis and atlas (p value 0.007).
  
  
  CONCLUSIONS
  The selected morphometries successfully characterised conformational changes in the brain and craniocervical junction that might form the basis of a diagnostic tool for all breeds. The severity of SM involved a spectrum of abnormalities, incurred by changes in both angulation and size that could alter neural parenchyma compliance and/or impede cerebrospinal fluid channels.
authors.affiliation: School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
authors.forename: Susan P
authors.identifier: http://orcid.org/0000-0001-8727-8440
authors.initials: SP
authors.lastname: Knowler
authors.affiliation: Department of Equine and Small Animal Medicine, 00014 University of Helsinki, Finland.
authors.forename: Anna-Mariam
authors.initials: AM
authors.lastname: Kiviranta
authors.affiliation: akm-stats, Glasgow, Scotland, United Kingdom.
authors.forename: Angus K
authors.initials: AK
authors.lastname: McFadyen
authors.affiliation: Department of Equine and Small Animal Medicine, 00014 University of Helsinki, Finland.
authors.forename: Tarja S
authors.initials: TS
authors.lastname: Jokinen
authors.affiliation: School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
authors.forename: Roberto M
authors.initials: RM
authors.lastname: La Ragione
authors.affiliation: School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.|Fitzpatrick Referrals, Godalming, Surrey, United Kingdom.
authors.forename: Clare
authors.initials: C
authors.lastname: Rusbridge
mesh_terms: D000818:Animals; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000000981:diagnostic imaging / Q000235:genetics / Q000662:veterinary*; D001947:Breeding; D002508:Cephalometry; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D003398:Craniosynostoses / Q000000981:diagnostic imaging / Q000235:genetics / Q000662:veterinary; D016002:Discriminant Analysis; D004283:Dog Diseases / Q000000981:diagnostic imaging* / Q000235:genetics / Q000473:pathology; D004285:Dogs; D005260:Female; D005539:Foramen Magnum / Q000000981:diagnostic imaging; D020022:Genetic Predisposition to Disease; D008279:Magnetic Resonance Imaging; D008297:Male; D010641:Phenotype; D012189:Retrospective Studies; D012249:Rhombencephalon / Q000000981:diagnostic imaging*; D012886:Skull / Q000000981:diagnostic imaging*; D019291:Skull Base / Q000000981:diagnostic imaging; D013595:Syringomyelia / Q000000981:diagnostic imaging / Q000209:etiology / Q000235:genetics / Q000662:veterinary*