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Brain tumors exert their clinical effects in a variety of ways. Mass effect, edema, seizures, and a vicious cycle of cause and effect are often the focus of therapeutic interventions employed to improve clinical signs and increase survival time. Obstructive hydrocephalus is a common sequela of certain types of brain tumors and is often the major driver of clinical signs seen in tumors arising within the ventricular system. This study outlines the application of ventriculoperitoneal shunting for obstructive hydrocephalus secondary to brain tumors as part of an overall management program to help increase patients' lifespan and quality of life., Competing Interests: Disclosure The authors declare that this chapter was written in the absence of any commercial or financial relationsips that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Dogs with internal hydrocephalus do not necessarily have high intraventricular pressure (IVP)., Hypothesis/objectives: Not all reported MRI findings indicate high IVP and some clinical signs might be associated with elevated IVP and syringomyelia., Animals: Fifty-three dogs., Materials and Methods: Cross-sectional study. Clinical signs and MRI findings were evaluated for an association of IVP >12 mm Hg and syringomyelia., Results: High IVP was associated with obtundation OR 4.64 (95% CI 1.27-16.93) (P = .02), head tilt OR 6.42 (95% CI 1.08-37.97) (P = .04) and nystagmus OR 8.24 (95% CI 1.44-47.07) (P = .02). Pain was associated with syringomyelia OR 3.4 (95% CI 0.98-11.78) (P = .05). The number of affected ventricles was associated with high IVP OR 2.85 (95% CI 0.97-8.33) (P = .05) and syringomyelia OR 12.74 (95% CI 2.93-55.4) (P = .0007). Periventricular edema OR 24.46 (95% CI 4.54-131.77), OR 7.61 (95% CI 1.91-30.32) (P < .0002, P = .004) and signal void sign OR 17.34 (95% CI 4.01-74.95), OR 4.18 (95% CI 1.16-15.02) (P < .0001, P = .03) were associated with high IVP and syringomyelia. The probability for syringomyelia is lower with disruption of the internal capsule OR 0.19 (95% CI 0.05-0.72) (P = .01) and higher VBR OR 0.25 (95% CI 0.1-0.63) (P = .004)., Conclusions and Clinical Importance: Previously reported MRI findings are not predictive of high IVP. Clinical signs and MRI findings should be used to make a diagnosis of internal hydrocephalus in dogs with or without high IVP., (© 2024 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objective: To describe the approach for placement of a transcerebellar fourth ventriculoperitoneal shunt for management of presumed fourth ventricle arachnoid diverticulum and secondary obstructive hydrocephalus of a dog. To describe the outcome of this procedure., Study Design: Case report., Animals: Male entire English springer spaniel, 3 years 9 months of age., Methods: The dog was initially presented for management of acute, progressive, and multifocal brainstem and forebrain dysfunction. Magnetic resonance imaging revealed internal obstructive hypertensive hydrocephalus. The dog was managed via ventriculoperitoneal shunting from the left lateral ventricle and made an excellent recovery. The dog acutely deteriorated 18 months after initial discharge and follow-up magnetic resonance imaging confirmed the ventricular shunt remained in situ with normal-sized lateral ventricles but revealed a cystlike lesion within the fourth ventricle, presumed to be a fourth ventricle arachnoid diverticulum. The diverticulum was causing mass effect and resultant compression of adjacent neuroparenchyma. A second ventriculoperitoneal shunt was subsequently placed into the fourth ventricle via the caudal cranial fossa and cerebellum. This was attached to a three-way connector, to which the existing shunt (within the left lateral ventricle) was also attached, and then secured to the existing medium-pressure valve., Results: Postoperatively, the dog immediately developed mild vestibular-cerebellar ataxia, with a marked improvement after 3 months. There were no shunt-associated complications. Long-term follow up at 40 months after the second surgical procedure revealed a normal neurological examination., Conclusion: Transcerebellar ventriculoperitoneal shunt placement for treatment of a presumed fourth ventricle arachnoid diverticulum was performed and was associated with a favorable long-term outcome., (© 2024 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Background: Neurofilament light chain (NfL) is released into the peripheral circulation by damaged axons., Objectives: To evaluate the diagnostic value of serum NfL concentration in dogs with intracranial diseases., Animals: Study included 37 healthy dogs, 31 dogs with idiopathic epilepsy (IE), 45 dogs with meningoencephalitis of unknown etiology (MUE), 20 dogs with hydrocephalus, and 19 dogs with brain tumors., Methods: Cohort study. Serum NfL concentrations were measured in all dogs using single-molecule array technology., Results: Serum NfL concentration in dogs with each structural disease was significantly higher than in healthy dogs and dogs with IE (P = .01). The area under the receiver operating characteristic curve of NfL for differentiating between dogs with structural diseases and IE was 0.868. An optimal cutoff value of the NfL 27.10 pg/mL had a sensitivity of 86.67% and a specificity of 74.19% to differentiate the dogs with IE from those with structural brain diseases. There were significant correlations between NfL concentrations and lesion size: (1) MUE, P = .01, r = 0.429; (2) hydrocephalus, P = .01, r = 0.563., Conclusions and Clinical Importance: Serum NfL could be a useful biomarker for distinguishing IE from structural diseases in dogs and predicting the lesion sizes of MUE and hydrocephalus., (© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

A 7-month-old male French bulldog was referred for abnormal mentation and gait. Physical examination revealed a dome shaped calvarium and persistent bregmatic fontanelle. Neurological examination revealed proprioceptive ataxia, pelvic limb paraparesis and strabismus with moderate ventriculomegaly, thinning of the cerebral parenchyma, and widened cerebral sulci on magnetic resonance imaging. Masses were identified in the region of the thyroid, which appeared heterogeneous and hyperintense in T1-weighted and T2-weighted compared with the adjacent muscle signal masses were identified. Radiological diagnosis was hydrocephalus "ex vacuo" and goiter. Blood test revealed abnormally low total thyroxine (TT4), free thyroxine (FT4), and normal thyrotropin concentration. A diagnosis of congenital hypothyroidism was confirmed by positive genetic test for thyroid peroxidase mutation. Thyroxine supplementation treatment rapidly improved clinical signs., (© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Ependymal cysts represent congenital brain malformations rarely described in human medicine, where surgical resection is the treatment of choice. In veterinary medicine, only three cases have been previously reported, with one partially resected with surgery. A 6 yr old entire male American Staffordshire terrier was referred with a 4 mo history of incoordination and collapsing episodes with extensor rigidity. Neurological examination localized the lesion to the left central vestibular system and cerebellum. A brain computed tomography scan showed a hypoattenuating lesion with peripheral contrast enhancement in the fourth ventricle consistent with a cyst and secondary hydrocephalus. Treatment with prednisone was initiated, but despite an initial improvement, neurologic signs recurred and a suboccipital craniectomy to remove the cyst was performed. The cyst was first drained, and the capsule was carefully resected. The histopathological evaluation revealed a simple cubic to cylindrical epithelium with apical cilia and loose surrounding fibrillar tissue consistent with an intraventricular ependymal cyst. Four and a half years after surgery, the dog only shows short episodes of balance loss when turning abruptly but is otherwise neurologically normal. To the authors' knowledge, this is the first reported ependymal cyst in the fourth ventricle of a dog with successful surgical resection., (© 2024 by American Animal Hospital Association.)

Background: Overshunting and hemispheric collapse are well-known complications after ventriculoperitoneal shunt (VPS) implantation. Risk factors that predispose to overshunting, treatment options, and prognosis after therapeutic intervention have not been described., Hypothesis/objectives: To identify preoperative risk factors for overshunting, the effect of surgical decompression, and their outcomes., Animals: Seventy-five dogs and 7 cats., Methods: Retrospective case cohort study. Age, breed, sex, body weight, number of dilated ventricles, ventricle brain ratio, intraventricular pressure, and implanted pressure valve systems were evaluated as possible risk factors., Results: Overshunting had a prevalence of 18% (Cl 95% 9.9-26.66). An increase of 0.05 in VBR increased the risk of overshunting by OR 2.23 (Cl 95% 1.4-3.5; P = .001). Biventricular hydrocephalus had the highest risk for overshunting compared to a tri- (OR 2.48 with Cl 95% 0.5-11.1) or tetraventricular hydrocephalus (OR 11.6 with Cl 95% 1.7-81.1; P = .05). There was no influence regarding the use of gravitational vs differential pressure valves (P > .78). Overshunting resulted in hemispheric collapse, subdural hemorrhage, and peracute deterioration of neurological status in 15 animals. Subdural hematoma was removed in 8 dogs and 2 cats with prompt postoperative improvement of clinical signs., Conclusions and Clinical Importance: Biventricular hydrocephalus and increased VBR indicate a higher risk for overshunting. The use of differential valves with gravitational units has no influence on occurrence of overshunting related complications and outcomes. Decompressive surgery provides a favorable treatment option for hemispheric collapse and has a good outcome., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.)

Background: Atlanto-axial (AA) subluxation can be a complex syndrome in dogs. Accurate identification and assessment of this condition are key to providing treatment and resolution., Aim: The purpose of this retrospective study was to describe the magnetic resonance imaging (MRI) characteristics of AA subluxation and associated neurologic deficits., Methods: A multicenter review of dogs with a diagnosis of AA subluxation was conducted, evaluating signalment, neurologic grade, duration of signs, and MRI characteristics. MRI characteristics included degree of spinal cord compression and joint subluxation, integrity of odontoid ligaments, presence of a dens, spinal cord signal intensity, and presence of syringohydromyelia, hydrocephalus, and Chiari-like malformation. A control population with normal AA joints was also evaluated. MR images of 42 dogs with AA subluxation were compared to 26 age and breed-matched control dogs., Results: Affected dogs had a median age of 27 months and a median weight of 2.7 kg, and the most commonly affected breed was the Yorkshire terrier (47.5%). Spinal cord signal hyperintensity, increased AA joint size, and cross-sectional cord compression at the level of the dens and mid-body C2 were associated with AA subluxation. No associations were found between cord compression, the appearance of the dens, or cord signal intensity and neurologic grade. Affected dogs did not have a higher incidence of Chiari-like malformation, syringohydromyelia, or hydrocephalus than control dogs, and their neurologic grade was not associated with MRI findings. Lack of dens and/or odontoid ligaments was associated with larger subluxations., Conclusion: Dogs with clinical signs of AA subluxation were significantly more likely to have intramedullary hyperintensity at the level of compression ( p = 0.0004), an increased AA joint cavity size ( p = 0.0005), and increased spinal cord compression at the level of dens and mid-body C2 ( p ≤ 0.05). The authors suggest an AA joint cavity size >1.4 mm and a subluxation distance >2.5 mm as cutoffs for MRI diagnosis of AA subluxation in dogs. No differences were noted between dogs with AA subluxation and control dogs regarding syringohydromyelia, hydrocephalus, and Chiari-like malformation., Competing Interests: The authors declare that there are no known conflicts of interest associated with this publication and there was no financial support necessary for this work that could have influenced the outcome.

Obstructive or nonobstructive hypertensive hydrocephalus is reported in choroid plexus tumors. Choroid plexus tumors typically present as T2-weighted hyperintense intraventricular masses with occasional cerebrospinal fluid-drop metastasis. Acquired neoplastic nonobstructive hydrocephalus without visible mass lesion in magnetic resonance imaging is not reported in dogs. A 4.5-year-old Rhodesian Ridgeback presented with reduced mental status, unilaterally absent pupillary light reflex, and neck pain. Magnetic resonance imaging revealed a nonobstructive hydrocephalus and widened lumbar subarachnoid space with no evidence of a primary mass lesion. Postmortem examination confirmed a disseminated choroid plexus tumor affecting the ependyma and choroid plexi of all ventricles and the cerebral and lumbar subarachnoid space. Disseminated choroid plexus carcinomatosis should be considered as a possible cause of hypertensive hydrocephalus even in absence of a primary mass., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.)

Background: Congenital obstructive hydrocephalus generates progressive irreversible fetal brain damage by ventricular enlargement and incremental brain tissue compression that leads to maldevelopment and poor clinical outcomes. Intrauterine treatments such as ventriculo-amniotic shunting have been unsuccessfully tried in the eighties., Objective: To assess if prenatal endoscopic third ventriculostomy (ETV) is feasible in a large animal model and optimize this technique for ventricular decompression and potential arrest of fetal brain damage in fetal lambs., Methods: We generated hydrocephalus in 50 fetal lambs by injecting a polymeric agent into the cisterna magna at midgestation (E85). Subsequently, 3 weeks later (E105), fetal ETV was performed using a small rigid fetoscope. The endoscopy entry point was located anterior to the coronal suture, 7 mm from the midline., Results: We obtained clear visualization of the enlarged lateral ventricles by endoscopy in the hydrocephalic fetal lambs. The floor of the third ventricle was bluntly perforated and passed with the scope for a successful ETV. Total success was achieved in 32/50 cases (64%). Causes of failure were blurred vision or third ventricle obliteration by BioGlue in 10/50 (20%) cases, anatomic misdirection of the endoscope in 5 (10%) cases, 2 cases of very narrow foramen of Monro, and 1 case of choroid plexus bleeding. If we exclude the cases artificially blocked by the polymer, we had a successful performance of prenatal-ETV in 80% (32/40) of hydrocephalic fetuses., Conclusion: Despite the inherent difficulties arising from ovine brain anatomy, this study shows that innovative fetal ETV is technically feasible in hydrocephalic fetal lambs., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Congress of Neurological Surgeons.)

Background: Pituitary apoplexy refers to hemorrhage or infarction within the pituitary gland resulting in acute neurological abnormalities. This condition is poorly described in dogs., Objectives: To document presenting complaints, examination findings, endocrinopathies, magnetic resonance imaging (MRI), treatments, and outcomes of dogs with pituitary apoplexy., Animals: Twenty-six client-owned dogs with acute onset of neurological dysfunction., Methods: Retrospective case series. Dogs were diagnosed with pituitary apoplexy if MRI or histopathology documented an intrasellar or suprasellar mass with evidence of hemorrhage or infarction in conjunction with acute neurological dysfunction. Clinical information was obtained from medical records and imaging reports., Results: Common presenting complaints included altered mentation (16/26, 62%) and gastrointestinal dysfunction (14/26, 54%). Gait or posture changes (22/26, 85%), mentation changes (18/26, 69%), cranial neuropathies (17/26, 65%), cervical or head hyperpathia (12/26, 46%), and hyperthermia (8/26, 31%) were the most frequent exam findings. Ten dogs (38%) lacked evidence of an endocrinopathy before presentation. Common MRI findings included T1-weighted hypo- to isointensity of the hemorrhagic lesion (21/25, 84%), peripheral enhancement of the pituitary mass lesion (15/25, 60%), brain herniation (14/25, 56%), and obstructive hydrocephalus (13/25, 52%). Fifteen dogs (58%) survived to hospital discharge. Seven of these dogs received medical management alone (median survival 143 days; range, 7-641 days) and 8 received medications and radiation therapy (median survival 973 days; range, 41-1719 days)., Conclusions and Clinical Importance: Dogs with pituitary apoplexy present with a variety of acute signs of neurological disease and inconsistent endocrine dysfunction. Dogs that survive to discharge can have a favorable outcome., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

The ability to differentiate clinical ventriculomegaly from incidental ventricular enlargement remains a challenge in veterinary radiology. Dilatation of one or both olfactory lobe recesses is occasionally seen on MRI of the brain in otherwise normal cats. The purpose of this study was therefore to determine the prevalence of this finding within a population of neurologically normal and neurologically abnormal cats, and to investigate associations with signalment, clinical and neurological examination findings, and MRI features. An observational retrospective cohort study was performed, and archived records were searched for cats that had undergone MRI of the head, including the olfactory lobes. Medical data and MRI parameters were recorded. One hundred fifty-one cats were included, with olfactory recess dilatation present in 56 cats. In 16 neurologically normal cats, olfactory recess dilatation was the only MRI finding. Olfactory recess dilatation was not associated with age, sex, breed, or with the presence of nasal disease. A significant association was found between generalized ventriculomegaly (P = 0.001) and the presence of CSF abnormalities (P = 0.036). Eleven percent of our cohort (16/151) demonstrated olfactory recess dilatation in the absence of other neurological or structural intracranial disease, suggesting that this may be seen as a normal variation in some cats., (© 2023 The Authors. Veterinary Radiology & Ultrasound published by Wiley Periodicals LLC on behalf of American College of Veterinary Radiology.)

Background: Intraventricular tumors are rare, optimal treatment is not defined. Symptomatic patients often exhibit life-threatening hydrocephalus. With several months time-to-effect after radiotherapy (RT), increased intracranial pressure is concerning. This increase in pressure can be overcome by ventriculoperitoneal shunting (VPS)., Objectives: Retrospective evaluation of outcome and complications in dogs and cats with intracranial tumors treated with either RT or VPS/RT., Animals: Twelve client-owned cats and dogs., Methods: Dogs and cats with symptomatic intraventricular tumors treated with definitive-intent RT or VPS/RT were included in a retrospective, descriptive case series. Complications, tumor volume evolution, time-to-progression, and survival time were determined., Results: Twelve animals were included: 1 cat and 5 dogs treated with single-modality RT and 4 cats and 2 dogs treated with VPS/RT. Neurological worsening seen in 4/6 animals during single-modality RT and 2/6 died during RT (suspected brain herniation). All dogs with VPS normalized clinically by the end of RT or earlier. Complications occurred in 4/6 animals, all but 1 were successfully managed surgically. Imaging follow-up in 8 animals surviving RT showed a marked decrease in tumor volume. Median survival time was 162 days (95% confidence interval [CI]: 16; infinity) for animals treated with RT and 1103 days (95%CI: 752; infinity) for animals treated with VPS/RT. Median time-to-progression was 71 days (95%CI: 7; infinity) and 895 days (95%CI: 704; infinity) for each group, respectively. Two dogs died because of intraventricular metastasis 427 and 461 days after single-modality RT., Conclusions and Clinical Importance: Ventriculoperitoneal shunting led to rapid normalization of neurological signs and RT had a measurable effect on tumor volume. Combination of VPS/RT seems to be beneficial., (© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

The objective of this study was to calculate lateral ventricles dimension in Cavalier King Charles Spaniel dogs with Chiari-like malformation and investigate the association between ventriculomegaly and signalment, clinical signs, ventricular asymmetry, grade of Chiari-like malformation, syringomyelia and index of medullary kinking. Retrospectively, 43 client-owned Cavalier King Charles Spaniels, older than 1 year of age, with magnetic resonance imaging diagnosis of Chiari-like malformation were enrolled. Initial and follow-up (up to 36 months) clinical status was graded. Images were reviewed to quantify the enlargement of lateral ventricles, evaluate ventricular symmetry, grade of Chiari-like malformation, grade of syringomyelia and medullary kinking index. Cases presenting epileptic seizures during the evaluation period were also recorded. The most common initial clinical signs were scratching and neck pain. Ventriculomegaly was identified in 70% of dogs, Chiari-like malformation grade 2 was observed in 77% of cases, ventricular asymmetry and syringomyelia were identified in 54% and 80% of dogs, respectively; the median medullary kinking index was 37.77%. Moreover, 28% of dogs presented epileptic seizures. No significant association was identified between dimension of lateral ventricles and signalment, clinical signs, and imaging findings; no significant association was identified between ventriculomegaly and epilepsy (P≥0.05). In conclusion, the prevalence of ventriculomegaly in Cavalier King Charles Spaniels is high but this finding does not seem related to the severity of clinical signs, presence of Chiari-like malformation, syringomyelia and craniocervical junction abnormalities such as medullary kinking.