Objectives This study aimed to investigate differences and demonstrate a normal range of morphological variation of the caudal fossa of the cranium of domestic cats. Methods CT scans of 32 domestic cat heads of 11 breeds were included. Isosurfaces from skulls were characterised through three-dimensional geometric morphometrics using geographical landmarks placed on the internal surface of the caudal fossa and foramen magnum. Raw data was transformed with a Procrustes fit and coordinate covariance was analysed by principal components to establish breed- and sex-level differences. Skulls were also classified according to the number of concavities along the mid-sagittal vermiform impression. Differences were investigated between breed groups and sex, and correlation was sought with age. Results Analyses revealed size-independent differences in occipital bone morphology across breeds and sex; however, no clustering was evident. Most variability was observed at the exoccipital bones, ventral portion of the supraoccipital bone, dorsum sellae of the basisphenoid and the osseous tentorium cerebelli. No statistically significant differences were identified via two-sample t-tests between breed groups or sexes. No statistically significant correlation using Spearman rho correlation coefficient was identified with age. Conclusions and relevance The feline caudal fossa displays a wide range of intra- and inter-breed variation, not linked to age or sex. Concavities along the vermiform impression have not previously been described. As advanced imaging modalities are becoming more frequently used for domestic felids, an established range of normality is important for discriminating pathological changes from anatomical variances.

The aim of this study was to investigate potential differences and correlations between brain and skull morphology and the clinical signs of brachycephalic dogs with and without Chiari-like malformation (CLM). Various measurements were derived from magnetic resonance images of the brain and craniocervical junction of thirty brachycephalic dogs in a flexed-neck position. Each dog was assigned a clinical grade. The distance from the planum of the foramen magnum to the pons was significantly reduced, providing evidence of craniocephalic disproportion similar to human patients with Chiari malformation type I. Cerebral length relative to cranial length was significantly increased in dogs with CLM compared with control dogs, supporting the hypothesis that CLM is governed by a global overcrowding of the brain, dissimilar to the human condition. Significant correlations were identified between these measurements and the extent of cerebellar herniation. No significant differences or correlations were identified with clinical grade. This is the first described morphometric analysis to use a strictly brachycephalic study population inclusive of a control group free from CLM.

A miniature poodle and miniature schnauzer were referred for the investigation of shallow breathing and restless behaviour, and the investigation of bilious vomiting, diarrhoea and the presence of a hepatic mass, respectively. In both cases, CT revealed heterogeneous, hyperattenuating content within the gall bladder, a defect in the gall bladder wall and leakage of biliary content into the perihepatic region compatible with gall bladder mucocele, rupture of the gall bladder and bile peritonitis. Both dogs underwent a cholecystectomy and made uneventful recoveries. Follow-up was available for both dogs one and two months later which confirmed a return to good health. CT is a helpful aid in the presurgical diagnosis of gall bladder wall rupture and bile peritonitis in dogs.