Case Report: Suspected hereditary spontaneous hydrocephalus in a Beagle pedigree

Hydrocephalus is one of the most common malformations in dogs and poses considerable treatment challenges in veterinary clinical practice. Ventricular enlargement may represent an early manifestation of hydrocephalus and is commonly quantified by the ventricle-to-brain index (VBI). This report presents a Beagle pedigree with suspected hereditary lateral ventricular enlargement, confirmed by VBI calculated from magnetic resonance imaging (MRI).

A 1.4-year-old female Beagle presented with severe hydrocephalus (VBI: 0.72) and complete absence of the parietal lobe. Its sire (ID: 11771, VBI = 0.61) showed hydrocephalus, whereas its dam had minimal lateral ventricular enlargement (VBI = 0.52), implying that the severe hydrocephalus in dog 90044 may have been paternally inherited. Additionally, a second cousin of dog 11771 displayed hydrocephalus, reinforcing the suspicion of a hereditary basis for the condition. To further investigate, we collated phenotypic data from 37 surviving offspring (out of 41) spanning six litters sired by dog 11771. To investigate age-related changes in lateral ventricular volume, we divided the pedigree members into three groups: puppies (<6 months old), juveniles (6-12 months old), and adults (≥12 months old). When assessed using a four-tier VBI classification, a Jonckheere-Terpstra test revealed that VBI and severity grades increased significantly with age, demonstrating progressive lateral ventricular enlargement from puppyhood to adulthood. To further investigate whether the VBI of the 11771 pedigree was abnormally enlarged, we compared its VBI and severity grades to those from 24 healthy Beagles (nine juveniles and 15 adults). Age-stratified comparisons showed that the VBI and severity grades of both juveniles and adults in this pedigree were significantly higher than those of controls.

Although limited by a small sample size from a single pedigree and the absence of long-term follow-up, this case report describes a Beagle pedigree with suspected hereditary, age-dependent progressive lateral ventricular enlargement. This finding provides a valuable reference for the early detection of hydrocephalus, evaluation of treatment efficacy, and assessment of prognostic outcomes.