Comparison of the endocranial- and brain volumes in brachycephalic dogs, mesaticephalic dogs and Cavalier King Charles spaniels in relation to their body weight

Abstract

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.

Clinical and Diagnostic Imaging Features of Brain Herniation in Dogs and Cats

“…Both brachycephalic dogs and CKCS have been reported to have larger total brain volumes relative to their weights compared to mesaticephalic dogs . Furthermore, brachycephalic dogs and CKCS demonstrated a smaller increase in subarachnoid space compared to mesaticephalic dogs as body weight increased . These results suggest that not only is body weight important but breed and head shape further influence the caudal fossa anatomy.…”

“…Prior studies have investigated relationships between breed, head shape and caudal fossa anatomy, most extensively in CKCS . A positive correlation between increasing body weight and caudal fossa size has been consistently demonstrated.…”

“…A positive correlation between increasing body weight and caudal fossa size has been consistently demonstrated. However, there have been conflicting reports regarding the relative volume of hindbrain parenchyma between various brachycephalic and mesaticephalic breeds . Both brachycephalic dogs and CKCS have been reported to have larger total brain volumes relative to their weights compared to mesaticephalic dogs .…”

“…However, there have been conflicting reports regarding the relative volume of hindbrain parenchyma between various brachycephalic and mesaticephalic breeds . Both brachycephalic dogs and CKCS have been reported to have larger total brain volumes relative to their weights compared to mesaticephalic dogs . Furthermore, brachycephalic dogs and CKCS demonstrated a smaller increase in subarachnoid space compared to mesaticephalic dogs as body weight increased .…”

“…In humans, landmarks and measurements defining herniation have been established on brain MRIs but such measurements have not been reported in dogs and cats . Morphometric analysis of the caudal fossa using MRI in Chiari‐like malformation in Cavalier King Charles Spaniels (CKCS) and Brussels Griffons is reported but the definition of FMH was variable . The aims of this study were to define the normal position of cerebellum and brainstem structures within the calvarium utilizing morphometric analysis of normal dog and cat brain MRIs, to compare these measurements to those obtained from dogs and cats with CTH, FMH or both identified on MRI by a radiologist, and, in this affected population, to determine if there is an association between severity of brain herniation defined using these MRI‐based measurements, presence of clinical signs and short‐term outcome.…”