MRI-based morphometric analysis in relation to Chiari-like malformation in brachycephalic canine breeds

Aims of this study were to investigate potential differences and correlations between brain and skull morphology and 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 30 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.