Use of Morphometric Mapping to Characterise Symptomatic Chiari-Like Malformation, Secondary Syringomyelia and Associated Brachycephaly in the Cavalier King Charles Spaniel.

Susan P Knowler,Zoha Kibar,Anna Tauro,Chloe Cross,Sandra Griffiths,Angus K Mcfadyen,Roberto M La Ragione,Clare Rusbridge,Colin J Driver,Jelena Jovanovik,Claire Wade

doi:10.1371/journal.pone.0170315

Susan P Knowler, Zoha Kibar + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0170315

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Journal: PloS one	Publication Date: Jan 25, 2017
Citations: 24	License type: CC BY 4.0

Affiliation: University of Surrey, Université de Montréal

Abstract

ObjectivesTo characterise the symptomatic phenotype of Chiari-like malformation (CM), secondary syringomyelia (SM) and brachycephaly in the Cavalier King Charles Spaniel using morphometric measurements on mid-sagittal Magnetic Resonance images (MRI) of the brain and craniocervical junction.MethodsThis retrospective study, based on a previous quantitative analysis in the Griffon Bruxellois (GB), used 24 measurements taken on 130 T1-weighted MRI of hindbrain and cervical region. Associated brachycephaly was estimated using 26 measurements, including rostral forebrain flattening and olfactory lobe rotation, on 72 T2-weighted MRI of the whole brain. Both study cohorts were divided into three groups; Control, CM pain and SM and their morphometries compared with each other.ResultsFourteen significant traits were identified in the hindbrain study and nine traits in the whole brain study, six of which were similar to the GB and suggest a common aetiology. The Control cohort had the most elliptical brain (p = 0.010), least olfactory bulb rotation (p = 0.003) and a protective angle (p = 0.004) compared to the other groups. The CM pain cohort had the greatest rostral forebrain flattening (p = 0.007), shortest basioccipital (p = 0.019), but a greater distance between the atlas and basioccipital (p = 0.002) which was protective for SM. The SM cohort had two conformation anomalies depending on the severity of craniocervical junction incongruities; i) the proximity of the dens (p <0.001) ii) increased airorhynchy with a smaller, more ventrally rotated olfactory bulb (p <0.001). Both generated ‘concertina’ flexures of the brain and craniocervical junction.ConclusionMorphometric mapping provides a diagnostic tool for quantifying symptomatic CM, secondary SM and their relationship with brachycephaly. It is hypothesized that CM pain is associated with increased brachycephaly and SM can result from different combinations of abnormalities of the forebrain, caudal fossa and craniocervical junction which compromise the neural parenchyma and impede cerebrospinal fluid flow.

Highlights

Syringomyelia (SM) secondary to Chiari-like Malformation (CM) in the Cavalier King Charles Spaniel (CKCS) has been well documented over the last decade [1,2,3]
Fourteen significant traits were identified in the hindbrain study and nine traits in the whole brain study, six of which were similar to the Griffon Bruxellois (GB) and suggest a common aetiology
Fitzpatrick Referrals Ltd, provided support in the form of salaries and materials for authors CD, JJ, AT and CR and the Goddard Veterinary Group provided the salary for SG

Summary

Introduction

Syringomyelia (SM) secondary to Chiari-like Malformation (CM) in the Cavalier King Charles Spaniel (CKCS) has been well documented over the last decade [1,2,3]. Reduced volume of the caudal fossa [10,11], cerebellar volume and herniation [12,13] medullary elevation (kinking) [13,14], jugular foramina [15,16], venous sinus volume [17] and atlanto-occipital overlapping [18,19] have all been shown to increase the risk of syringomyelia [20,21]. Evidence suggests that the early closure of skull bone sutures (craniosynostosis) in CKCS [9,22,23] and GB [15,24] reduces the size of the caudal fossa, alters the neuro-parenchymal morphology and disrupts cerebrospinal fluid (CSF) dynamics [20]. Some dogs with CM alone exhibit behavioural signs of pain

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