Premature closure of cranial base synchondroses has been proposed as the mechanism for brachycephaly in dogs and caudal occipital malformation syndrome (COMS) in Cavalier King Charles Spaniels. The purpose of this retrospective study was to compare times of closure for cranial base synchondroses in mesaticephalic, brachycephalic, and Cavalier King Charles Spaniel dogs. Cranial magnetic resonance imaging studies were retrieved for client-owned dogs less than 18 months of age. Breed, age, skull conformation, and the open or closed state of cranial base synchondroses were independently recorded by two observers. For dogs with a unanimous observer agreement, regression analysis was used to test effects of age and gender on the open or closed status of synchondroses and differences between groups. A total of 174 dogs were included in MRI interpretations and 165 dogs were included in the regression analysis. Statistically significant differences in closure time of the spheno-occipital synchondrosis were identified between brachycephalic and mesaticephalic dogs (P = 0.016), Cavalier King Charles Spaniels and mesaticephalic dogs (P < 0.0001), and Cavalier King Charles Spaniels and brachycephalic dogs (P = 0.014). Findings from the current study supported the theory that morphological changes leading to the skull phenotype of the Cavalier King Charles Spaniels could be due to an earlier closure of the spheno-occipital synchondrosis.

BackgroundA number of studies have attempted to quantify the relative volumes of the endocranial volume and brain parenchyma in association with the pathogenesis of the Chiari-like malformation (CLM) in the Cavalier King Charles spaniel (CKCS). In our study we examine the influence of allometric scaling of the brain and cranial cavity volume on morphological parameters in different dog breeds. MRI scans of 110 dogs (35 mesaticephalic dogs, 35 brachycephalic dogs, 20 CKCSs with SM, and 20 CKCSs without SM) have been used to create 3-dimensional volumetric models of skull and brain parts. Volumes were related to body weight calculating the adjusted means for different breeds.ResultsThere was a strong global dependency of all volumes to body weight (P < 0.0001). The adjusted means of the absolute and relative volumes of brain parenchyma and cranial compartments are not significantly larger in CKCSs in comparison to brachycephalic and mesaticephalic dogs. A difference in absolute or relative volumes between CKCSs with and without SM after relating these values to body weight could not be identified. The relative volume of the hindbrain parenchyma (caudal fossa parenchyma percentage) was larger in brachycephalic dogs than in CKCSs, without causing herniation or SM.ConclusionAn influence of body weight exist in dogs, which can be sufficiently large to render conclusions on the difference in volumes of the brain and skull unsafe unless some account of the body weight is taken in the analysis. The results of this study challenge the role of overcrowding for the development of SM in dogs.

A 7-year-old Afghan hound presented with a history of disorientation, loss of vision, and seizures. Magnetic resonance imaging helped identify a mass at the level of the main olfactory bulb that compressed and displaced adjacent tissues in the cribriform plate into the nasal cavity and nasopharynx. Bony structures were osteolytic. After removing almost 80% of the mass, the tumor recurred a few months later. Due to severe respiratory distress and subsequent to an ultrasound diagnosis of a liver tumor, the dog was euthanized. In addition to the nasal mass, a single nodule in the liver and multiple nodules in the lung were present. All masses had similar cell morphology and were diagnosed as metastasizing esthesioneuroblastoma. The neoplastic cells expressed neuron-specific enolase and chromogranin A, and a few cells within the nasal mass were positive for cytokeratin. This is the first description of a canine esthesioneuroblastoma with distant metastases.

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