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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.

Background Studies in animal models, in which internal hydrocephalus has been induced by obstructing the cerebrospinal fluid pathways, have documented an up-regulation of the concentrations of aquaporin-4 (AQP4) in the brain. In this study, the concentrations of aquaporin-1 (AQP1), AQP1, AQP4 and interleukin-6 (IL-6) were determined in the CSF of dogs with idiopathic communicating hydrocephalus before and after the reduction of intraventricular volume following ventriculo-peritoneal shunt (VP-shunt) treatment. Results The concentrations of AQP4 and IL-6 were increased in the cerebrospinal fluid of dogs with hydrocephalus compared to controls. Both parameters significantly decreased after surgical treatment, accompanied by decrease of ventricular size and the clinical recovery of the dogs. AQP1 was not detectable in CSF. Conclusions Brain AQP4 up-regulation might be a compensatory response in dogs with hydrocephalus. Future determination of AQP4 at the mRNA and protein level in brain tissue is warranted to substantiate this hypothesis.

This paper presents magnetic resonance imaging (MRI) findings of three dogs after carbon monoxide intoxication. In the first and second cases, MRI changes were confined to both caudate nuclei and in the first case also to the putamen as bilaterally symmetric diffuse homogenous T2 and FLAIR hyperintense, T1 hypointense lesions. No contrast enhancement was seen. In the third case MRI revealed multiple areas of hyperintensity bilaterally on T2 and FLAIR as well as ill-defined areas within the frontal, parietal and occipital grey matter. The caudal colliculi, globus pallidus, substantia nigra and central area of the thalamus showed bilaterally hyperintense lesions on T2w and FLAIR with moderate enhancement after intravenous contrast administration.

Background Acetazolamide is recommended for the reduction of cerebrospinal fluid production in canine internal hydrocephalus. The efficacy of the drug in terms of alleviation of the clinical symptoms and the restoration of normal ventricular volume has not been documented. We hypothesize that acetazolamide inadequately improve clinical signs and has no effect on the ventricular volume. Six dogs with internal hydrocephalus underwent neurological examination and were examined by magnetic resonance imaging, on the day of the diagnosis, after treatment with acetazolamide directly before surgery, and 6 weeks after implantation of a vetriculo-peritoneal shunt due to lack of improvement after medical therapy with 10 mg/kg acetazolamide three times daily (TID). The ventricular volume in relation to the total brain volume was determined on each occasion. The changes in relative ventricular volume and of the neurological status were assessed and compared. Results McNemar’s test revealed no significant differences in clinical symptoms before and after medical treatment (P > 0.05). However, clinical symptoms changed significantly after surgical treatment (P = 0.001). The ventricle-brain ratio was not significantly changed after therapy with acetazolamide (P > 0.05); however, after subsequent shunt implantation, it was significantly reduced (P = 0.001). Conclusion Acetazolamide (10 mg/kg TID) showed no effects on clinical signs or ventricular volume in dogs with internal hydrocephalus. After subsequent ventriculo-peritoneal shunting, the dogs had a significantly reduced cerebral ventricular volume and five out of six dogs had no abnormal findings in neurological examination.

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.