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

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.

Questionnaire‐based Analysis of Owner‐reported Scratching and Pain Signs in Cavalier King Charles Spaniels Screened for Chiari‐like Malformation and Syringomyelia

“…However, it is also possible that the pain is originating elsewhere in the pathways and SM is purely a surrogate. Indeed, a recent paper has discussed the potential interaction of morphological variables that might produce SM and pain . Additionally, neuropathic‐type pain results from changes in the functioning of the nervous system, and there is variability in the response of individuals to the same type of insult.…”

Behavioral and clinical signs of Chiari‐like malformation‐associated pain and syringomyelia in Cavalier King Charles spaniels

“…The resulting damage can cause pain, phantom scratching, scoliosis, paresis, and sensory deficits . Syringomyelia develops as a consequence of obstruction of cerebrospinal fluid (CSF) channels, and in the dog, it is most commonly associated with Chiari‐like malformation (CM), a complex developmental malformation of the skull and craniocervical vertebrae characterized by a conformational change and overcrowding of the brain and cervical spinal cord, particularly at the craniospinal junction …”

Network analysis of canine brain morphometry links tumour risk to oestrogen deficiency and accelerated brain ageing

“…5,42 Certain observations built confidence in our analysis, not least the relative ventriculomegaly in brachycephalic breeds, and cerebellar compression in CKCS dogs. 65,72,74 Enrichment of Boxers with tumours was anticipated 74 and the compromised septal integrity in this breed is more common in brachycephalics generally (29% versus 9% and 13% in mesocephalic and dolichocephalic breeds in our network, respectively). Non-detection of the canine septum pellucidum on MRI is largely considered incidental, 70,75-76 and it remains possible that the septum is intact, but too thin to be observed in some dogs.…”

“…With respect to breed group, the anomalous class was significantly enriched for Toy dogs (mainly CKCS reflecting the high prevalence of Chiari-like malformation in this breed), 65 whilst the tumour class was enriched for Working group dogs (mainly Boxers). Again, ventricular size strongly dictated clustering and group dynamics; four out of seven Labrador…”