Chiari-like malformation in the Griffon Bruxellois

Objectives: This study describes Chiari‐like malformation and syringomyelia in the Griffon Bruxellois and establishes if skull radiographs are useful for disease prediction. Methods: Magnetic resonance imaging from 56 Griffon Bruxellois dogs was assessed for Chiari‐like malformation and cerebrospinal fluid pathway abnormalities. Skull radiographs were obtained in 33 dogs. Two rostrocaudal and two ventrodorsal measurements were made, and ratios of one length to another were compared. Results: In this selected sample, 60·7 per cent had Chiari‐like malformation. Syringomyelia occurred with and without Chiari‐like malformation (37·5 and 8·9 per cent study population, respectively). The radiographic study demonstrated that one measurement ratio could be used to predict Chiari‐like malformation (sensitivity of 87 per cent and specificity of 78 per cent) and that there were significant interaction factors between sex and syringomyelia for two measurement ratios. Clinical Significance: The study suggests that Chiari‐like malformation is characterised by a shortening of the basicranium and supra‐occipital bone with a compensatory lengthening of the cranial vault, especially the parietal bone. We described a simple radiographic technique, which may be useful as a screening test until a more definite genetic test for Chiari‐like malformation is available.