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Abstract Background Data regarding congenital sensorineural deafness (CSD) in client‐owned, white Devon Rex cats is limited because most of the information on this disease comes from experiments on mixed‐breed cats. Objectives Provide data on the occurrence of CSD in a population of client‐owned purebred white Devon Rex cats. Animals Forty client‐owned, purebred, white Devon Rex cats examined at 2 different facilities. Median age of the examined cats was 19 weeks. Methods Hearing status was defined by use of brainstem auditory evoked responses. Results The occurrence of sensorineural deafness in the studied population of Devon Rex cats was estimated at 10%. Unilateral and bilateral deafness occurred equally often, with 2 individuals having each (ie, 5.0%). No association between the occurrence of CSD and sex could be found, χ2 (1, n = 40) = 0.001 (P > .99). No association between blue irises and deafness was noted in the studied population, χ2 (1, n = 40) .99). Conclusions The occurrence of CSD in a population of client‐owned, white Devon Rex cats was found to be lower compared with data obtained in previously conducted studies of deafness in purebred cats. In the studied population of Devon Rex cats, no association between blue irises and CSD was found.

Abstract Background Seizures are considered a clinical sign in dogs with internal hydrocephalus but are not found in recent studies. Seizure prevalence due to ventricular enlargement and the prevalence of postoperative seizures in animals is not known. Objectives To determine seizure prevalence in dogs and cats with idiopathic internal hydrocephalus, to identify risk factors for seizure development, and to determine seizure prevalence in a 2‐year period after ventriculo‐peritoneal shunting (VPS). Animals Records and MRIs of 197 animals from 2001 to December 2019 were investigated. A total of 121 animals (98 dogs and 23 cats) were included in the study. Methods A retrospective multicenter case cohort study was conducted. Databases were searched for dogs and cats with internal hydrocephalus. MRI and CSF examinations were evaluated for signs of additional underlying disorders. Prevalence of seizures was estimated for animals showing only hydrocephalus internus. Risk factors were evaluated according to age, morphometric and morphological findings in the brain. All animals that underwent surgery were reexamined 2 years after surgery. Results One hundred twenty‐one animals (98 dogs and 23 cats) with internal hydrocephalus met the inclusion criteria. Seizure prevalence in dogs and cats with internal hydrocephalus was low (1.7%;

Background One of the remaining questions in treating dogs with internal hydrocephalus is the association between the decrease of ventricular volume and re‐expansion of cerebral parenchyma with clinical improvement. Hypothesis A decrease in ventricular volume and re‐expansion of brain tissue occur after ventriculoperitoneal shunting (VPS). Clinical improvement defined by resolution of ≥1 clinical signs is associated with decreased size of cerebral ventricles and that the extent of change in ventricular size is associated with clinical improvement. Animals Forty‐five client‐owned dogs with newly diagnosed communicating internal hydrocephalus. Methods Ventricular volume, brain volume, and clinical status of dogs that underwent VPS were measured before and 3 months after surgery. Multiple logistic regression analysis was performed to assess the influence of decrease in ventricular size in addition to the covariates “age of the animal” and “duration of clinical signs before surgery” on improvement of clinical signs. Results Decreased volume of cerebral ventricles was associated with resolution of ≥1 preoperative clinical sign (P

Collapse of the lateral cerebral ventricles after ventriculo-peritoneal drainage is a fatal complication in dogs with internal hydrocephalus. It occurs due to excessive outflow of cerebrospinal fluid into the peritoneal cavity (overshunting). In most shunt systems, one-way valves with different pressure settings regulate flow into the distal catheter to avoid overshunting. The rationale for the choice of an appropriate opening pressure is a setting at the upper limit of normal intracranial pressure in dogs. However, physiological intraventricular pressure in normal dogs vary between 5 and 12 mm Hg. Furthermore, we hypothesise that intraventricular pressure in hydrocephalic dogs might differ from pressure in normal dogs and we also consider that normotensive hydrocephalus exists in dogs, as in humans. In order to evaluate intraventricular pressure in hydrocephalic dogs, twenty-three client owned dogs with newly diagnosed communicating internal hydrocephalus were examined before implantation of a ventriculo-peritoneal shunt using a single use piezo-resistive strain-gauge sensor (MicroSensor ICP probe). Ventricular volume and brain volume were measured before surgery, based on magnetic resonance images. Total ventricular volume was calculated and expressed in relation to the total volume of the brain, including the cerebrum, cerebellum, and brainstem (ventricle-brain index). Multiple logistic regression analysis was performed to assess the influence of the covariates "age", "gender", "duration of clinical signs", "body weight", and "ventricle-brain index" on intraventricular pressure. The mean cerebrospinal fluid pressure in the hydrocephalic dogs was 8.8 mm Hg (standard deviation 4.22), ranging from 3-18 mm Hg. The covariates "age", (P = 0.782), "gender" (P = 0.162), "body weight", (P = 0.065), or ventricle-brain index (P = 0.27)" were not correlated with intraventricular pressure. The duration of clinical signs before surgery, however, was correlated with intraventricular pressure (P< 0.0001). Dogs with internal hydrocephalus do not necessarily have increased intraventricular pressure. Normotensive communicating hydrocephalus exists in dogs.

The nature of ventriculomegaly in dogs is still a matter of debate. Signs of increased intraventricular pressure and atrophy of the cerebral white matter have been found in dogs with ventriculomegaly, which would imply increased intraventricular pressure and, therefore, a pathological condition, i.e., to some extent. Reduced periventricular blood flow was found in people with high elevated intraventricular pressure. The aim of this study was to compare periventricular brain perfusion in dogs with and without ventriculomegaly using perfusion weighted-magnetic-resonance-imaging to clarify as to whether ventriculomegaly might be associated with an increase in intraventricular pressure. Perfusion was measured in 32 Cavalier King Charles spaniels (CKCS) with ventriculomegaly, 10 CKCSs were examined as a control group. Cerebral blood flow (CBF) was measured using free-hand regions of interest (ROI) in five brain regions: periventricular white matter, caudate nucleus, parietal cortex, hippocampus, and thalamus. CBF was significantly lower in the periventricular white matter of the dogs with ventriculomegaly (p = 0.0029) but not in the other ROIs. Reduction of periventricular CBF might imply increase of intraventricular pressure in ventriculomegaly.

Large cerebral ventricles are a frequent finding in brains of dogs with brachycephalic skull conformation, in comparison with mesaticephalic dogs. It remains unclear whether oversized ventricles represent a normal variant or a pathological condition in brachycephalic dogs. There is a distinct relationship between white matter and grey matter in the cerebrum of all eutherian mammals. The aim of this study was to determine if this physiological proportion between white matter and grey matter of the forebrain still exists in brachycephalic dogs with oversized ventricles. The relative cerebral grey matter, white matter and cerebrospinal fluid volume in dogs were determined based on magnetic-resonance-imaging datasets using graphical software. In an analysis of covariance (ANCOVA) using body mass as the covariate, the adjusted means of the brain tissue volumes of two groups of dogs were compared. Group 1 included 37 mesaticephalic dogs of different sizes with no apparent changes in brain morphology, and subjectively normal ventricle size. Group 2 included 35 brachycephalic dogs in which subjectively enlarged cerebral ventricles were noted as an incidental finding in their magnetic-resonance-imaging examination. Whereas no significant different adjusted means of the grey matter could be determined, the group of brachycephalic dogs had significantly larger adjusted means of lateral cerebral ventricles and significantly less adjusted means of relative white matter volume. This indicates that brachycephalic dogs with subjective ventriculomegaly have less white matter, as expected based on their body weight and cerebral volume. Our study suggests that ventriculomegaly in brachycephalic dogs is not a normal variant of ventricular volume. Based on the changes in the relative proportion of WM and CSF volume, and the unchanged GM proportions in dogs with ventriculomegaly, we rather suggest that distension of the lateral ventricles might be the underlying cause of pressure related periventricular loss of white matter tissue, as occurs in internal hydrocephalus.