Subcortical and white matter alterations in canine ventriculomegaly: an observational volumetric and...

OBJECTIVE: Ventriculomegaly and hydrocephalus are frequently found during routine clinical imaging, and hydrocephalus in dogs has been shown to alter brain tissue. Although approaches exist to differentiate canine hydrocephalus from ventriculomegaly, information about brain tissue alterations in dogs with ventriculomegaly is lacking. In this observational study, we focused on ventriculomegaly and examined the cerebral anatomical adaptations that accommodate the increased ventricular volume. METHODS: 95 neuroradiological normal diagnosed dogs of different breeds were divided into the two groups, ventriculomegaly and control, according to morphological criteria and ventricle-brain-indices as determined by ratio of brain and lateral ventricle wide. Brain volumetry and voxel-based-morphometry (VBM) were conducted using automatic procedures employing the Statistical Parametric Mapping software and a canine brain atlas. RESULTS: Significant alterations in cingulate cortex, caudate nucleus, thalamus, hippocampus, geniculate body as well as corpus callosum were observed in dogs of the ventriculomegaly group by both volumetry and VBM. Interestingly, ventriculomegaly affected only lateral ventricles, the 3rd ventricle, and the mesencephalic aqueduct but not the 4th ventricle. DISCUSSION: A clear distinction between canine hydrocephalus and ventriculomegaly remains difficult and recent research suggests parallels between both. Advances in automated segmentation methods and voxel-based morphometry applicable to canine magnetic resonance imaging offer the opportunity to comprehensively assess structural abnormalities. In addition, clinical assessments are required to investigate the impact of ventriculomegaly on cognitive function and behavior in further studies. CONCLUSION: We propose the use of a lower ventricle-brain-index threshold of ≥ 0.5 to include all ventricle-associated tissue alterations with potential clinical manifestation.