Canine and feline intracranial meningiomas: An updated review

An Illustrated Scoping Review of the Magnetic Resonance Imaging Characteristics of Canine and Feline Brain Tumors

Magnetic resonance imaging (MRI) is used pervasively in veterinary practice for the antemortem diagnosis of intracranial tumors. Here, we provide an illustrated summary of the published MRI features of primary and secondary intracranial tumors of dogs and cats, following PRISMA scoping review guidelines. The PubMed and Web of Science databases were searched for relevant records, and input from stakeholders was solicited to select data for extraction. Sixty-seven studies of moderate to low-level evidence quality describing the MRI features of pathologically confirmed canine and feline brain tumors met inclusion criteria. Considerable variability in data inclusion and reporting, as well as low case numbers, prohibited comparative data analyses. Available data support a holistic MRI approach incorporating lesion number, location within the brain, shape, intrinsic signal appearances on multiparametric sequences, patterns of contrast enhancement, and associated secondary changes in the brain to prioritize differential imaging diagnoses, and often allows for accurate presumptive diagnosis of common intracranial tumors. Quantitative MRI techniques show promise for improving discrimination of neoplastic from non-neoplastic brain lesions, as well as differentiating brain tumor types and grades, but sample size limitations will likely remain a significant practical obstacle to the design of robustly powered radiomic studies. For many brain tumor variants, particularly in cats, there remains a need for standardized studies that correlate clinicopathologic and neuroimaging data.

Surgical treatment of feline intracranial meningiomas: a retrospective study of 26 cases

BACKGROUND

Surgical excision is the treatment of choice for feline intracranial meningioma.

OBJECTIVES

To report clinical findings, complications, and outcomes following surgery for feline intracranial meningioma.

METHODS

Medical records (01/2000-01/2017) of cats that underwent surgical excision of an intracranial meningioma at our institution were reviewed. Patient data included signalment, clinical signs, surgical technique, complications, histopathologic diagnosis, survival time, and owners' answers to a satisfaction questionnaire. Survival was assessed using the Kaplan-Meier method and log-rank test.

RESULTS

Twenty-six cats were included in this study. The exact cause of death was known in 17 cases and was not related to meningioma in 9/17 cases. Overall median survival time was 881 days (95% confidence interval 518; 1248). The age of the cat did not influence survival (p = 0.94) or the occurrence of complications (p = 0.051). Complications occurred in 13/24 cats, including dramatic complications in 4/24 cats. Most complications appeared in the first 24 hours post-surgery (12/13). Males had more postoperative complications (p = 0.042), including more seizures (p = 0.016). Cats with cranioplasty had fewer complications (p = 0.021). Clinical recurrence was confirmed in 3 out of 17 cats. Recurrence-free survival time was 826 days. Most owners (12/14) were satisfied with the outcome.

CONCLUSIONS

Surgical treatment of intracranial meningioma in cats was associated with a long median survival time but also with a high rate of minor and major postoperative complications, including early postoperative seizures. Cranioplasty may reduce complications. Age at the time of surgery had no effect on outcomes.

Diagnostic immunohistochemistry of primary and secondary central nervous system neoplasms of dogs and cats

The diagnosis of primary and secondary CNS neoplasms of dogs and cats relies on histologic examination of autopsy or biopsy samples. In addition, many neoplasms must be further characterized by immunohistochemistry (IHC) for a more refined diagnosis in specific cases. Given the many investigations assessing the diagnostic and prognostic IHC profile of CNS neoplasms in the veterinary literature, it may be difficult for the diagnostic pathologist or pathology trainee to narrow the list of reliable diagnostic IHCs when facing a challenging case. Here we compile a comprehensive list of the most diagnostically relevant immunomarkers that should be utilized for the diagnostic support or confirmation of the most common primary and secondary CNS neoplasms of dogs and cats.

Evaluation of the health-related quality of life in dogs following intracranial meningioma resection using a specifically developed questionnaire

As advanced treatments are becoming increasingly feasible in veterinary medicine, the evaluation of the health-related quality of life (HRQOL) of treated animals is becoming more relevant. We evaluated owner-perceived HRQOL of 10 dogs that underwent craniotomy for meningioma resection between 2002 and 2022 at our institution through telephone interview. For this purpose, we developed a disease-specific questionnaire containing 52 items (mostly of scoring nature) patterned after previously validated instruments and organised into eight domains. Approval by the Human Ethical Committee and respondents' consent were obtained. We analysed the scores for all domains and dogs. The effect of different variables on the HRQOL score was determined via log-rank test and Pearson correlation. Scores for all included dogs (range, 0-235 points) were totaled, with a higher number of points indicating a better HRQOL. The dogs included in this study yielded a mean score of 200.6 points (range, 176-227 points), implying a good overall quality of life. There were no significant associations between individual parameters and outcomes. Our questionnaire represents a structured tool for the specific evaluation of postoperative HRQOL in dogs with meningioma, placing a minimal burden on respondents. Few instruments have been developed to assess animal welfare in a disease-specific context. Implementing these tools, however, is essential to accurately evaluate not only the impact of treatments on biologic parameters, but also their implications on patient welfare. Thus, treatment plans may consider HRQOL for a more comprehensive clinical decision-making process.

Domestic Animal Models of Central Nervous System Tumors: Focus on Meningiomas

Intracranial primary tumors (IPTs) are aggressive forms of malignancies that cause high mortality in both humans and domestic animals. Meningiomas are frequent adult IPTs in humans, dogs, and cats, and both benign and malignant forms cause a decrease in life quality and survival. Surgery is the primary therapeutic approach to treat meningiomas, but, in many cases, it is not resolutive. The chemotherapy and targeted therapy used to treat meningiomas also display low efficacy and many side effects. Therefore, it is essential to find novel pharmacological approaches to increase the spectrum of therapeutic options for meningiomas. This review analyzes the similarities between human and domestic animal (dogs and cats) meningiomas by evaluating the molecular and histological characteristics, diagnosis criteria, and treatment options and highlighting possible research areas to identify novel targets and pharmacological approaches, which are useful for the diagnosis and therapy of this neoplasia to be used in human and veterinary medicine.

Computed tomographic, magnetic resonance imaging, and ultrasonographic characteristics of retrobulbar meningiomas in 15 dogs

Meningioma is the most common tumor of the cranium in dogs and an important differential diagnosis for a potentially treatable disease that can be found in the periorbital tissues. The objective of this retrospective, case series study was to describe the CT, MRI, and US characteristics of confirmed retrobulbar meningiomas in a group of dogs. Medical records from multiple institutions were searched for canine patients with CT, MRI, and/or US imaging of a cytologically or histologically confirmed retrobulbar meningioma. Fifteen dogs met the inclusion criteria. Retrobulbar meningiomas typically appeared as a relatively well-defined conical to ovoid mass within the retrobulbar space, most often along the optic nerve and expanding the extraocular muscle cone. On CT, masses were predominantly soft tissue attenuating and variably heterogeneously contrast enhancing. While MRI features were variable, moderate to marked contrast enhancement was seen in all cases. Many of the tumors had evidence of partial mineralization, best appreciated on CT in nine patients, but also suspected based on susceptibility artifacts in three MRI cases, one of which was confirmed on CT. Regional osteolysis was a rare finding, noted in three cases, but was often accompanied by cranial cavity extension (2/3). Cranial cavity extension was also seen in the absence of regional osteolysis, identified in a total of six patients. On US, masses were echogenic and compressed the globe. The findings were consistent with previous gross and histologic descriptions and supported prioritizing retrobulbar meningioma as a differential diagnosis for dogs with the described imaging characteristics.

The expression of platelet-derived growth factor and its receptor in canine and feline meningiomas

Feline meningiomas usually have benign biological behavior, while canine and human meningiomas are often classified as grade 2 or 3. Activation of the platelet-derived growth factor (PDGF) and its receptor signal pathway through PDGFβ/Rβ autocrine and paracrine is considered to play an important role in the tumor proliferation and malignant transformation of human meningiomas. However, there have been few studies about the expression of these molecules in canine meningiomas and no studies about their expression in feline meningiomas. We analyzed the PDGFα/Rα and PDGFβ/Rβ expression in canine and feline meningiomas by immunohistochemistry and western blotting. Immunohistochemically, most canine meningiomas showed the expression of PDGFα (42/44; 95.5%), PDGFRα (44/44; 100%) and PDGFRβ (35/44; 79.5%), and a few showed the expression of PDGFβ (8/44; 18.2%). In contrast, feline meningiomas were immunopositive for PDGFRα and PDGFRβ in all cases (14/14; 100%), while no or a few cases expressed PDGFα (0/14; 0%) and PDGFβ (2/14; 14.3%). Western blotting revealed specific bands for PDGFα, PDGFRα and PDGFRβ, but not for PDGFβ in a canine meningioma. In a feline meningioma, specific bands for PDGFRα and PDGFRβ were detected, but not for PDGFα and PDGFβ. These results suggested that canine meningiomas commonly express PDGFα/Rα, and thus autocrine or paracrine PDGFα/Rα signaling may be involved in their initiation and progression. Moreover, PDGF negativity may be related to benign biological behavior and a low histopathological grade in feline meningioma.

Outcome and quality of life after intracranial meningioma surgery in cats

OBJECTIVES

The present study aimed to evaluate the postoperative quality of life (QOL) after surgery for the treatment of intracranial meningioma in cats.

METHODS

The study included 14 cases that underwent craniotomy from May 2009 to March 2021. Owners were contacted via telephone after a median time of 967 (range 227-4209) days after surgery and surveyed with a specially designed questionnaire that consisted of three domains, subdivided into different items. Physical behaviour, including general condition, food intake, mobility and overall impression, was evaluated from 0, reflecting the worst status, to 10, reflecting the best. The development of preoperative existing clinical signs, seizures and concurrent medication were evaluated individually for each patient. The time span necessary for the improvement of each item was recorded. Finally, satisfaction about the decision for surgery was ranked from 0 to 10.

RESULTS

Thirteen questionnaires were completed. Three cats were evaluated twice owing to revision surgery. Owners reported a statistically significant (P <0.001) improvement from immediately after the operation to 240 days after surgery. Preoperative clinical signs resolved in 95% of cases. All questioned owners would opt for surgery again.

CONCLUSIONS AND RELEVANCE

QOL after surgery for intracranial meningioma in cats seems encouraging regarding our study. Nevertheless, limitations, such as small sample size, recall bias, lack of a control group and validation of the questionnaire, need to be kept in mind when interpreting the results.

A novel meningioma with tyrosine-rich crystals in a 6-year-old Great Dane

A 6-year-old female spayed Great Dane was evaluated for acute onset cluster seizures. Magnetic resonance imaging (MRI) identified a mass in the olfactory bulbs with a large mucoid component caudal to the primary mass. The mass was removed via transfrontal craniotomy and histopathology revealed a tyrosine crystalline-rich, fibrous meningioma with a high mitotic index. Repeat MRI at 6 months showed no detectable tumor regrowth. The dog is clinically normal with no seizures at the time of publication 10 months after surgery. This meningioma subtype is rare in humans. This unique meningioma occurred in a dog of younger age and uncommon breed for intracranial meningioma. Biological progression of this tumor subtype is unknown; however, growth rate might be slow despite the high mitotic index.

Use of Computed Tomography and Magnetic Resonance Angiograms Combined with a 3D Surgical Guide in an Elderly Cat with an Occipital Lobe Meningioma

We present a case of occipital lobe meningioma resection in an elderly cat. The surgery was performed with the goal of avoiding major bleeding. An 11-year-old castrated indoor-only male Persian Chinchilla (5.5 kg) was presented with a month-long history of progressive tetraparesis for a left occipital lobe meningioma. Magnetic resonance imaging revealed a T2-weighted heterogeneously hyperintensity and a T1-weighted well-contrast enhancing extradural mass in the left occipital lobe of the brain. Cerebral angiographic data were obtained using magnetic resonance (MRA) and computed tomography angiography (CTA). Advanced angiograms and virtual reconstruction of images revealed that the tumor was surrounded by the caudal parasagittal meningeal vein. A left caudal rostrotentorial craniotomy and en bloc resection of the tumor were performed, and histopathology revealed a meningioma. Complete neurological recovery was achieved within 10 days after surgery. To the best of our knowledge, this is the first case report describing CTA and MRA findings and favorable clinical outcomes after surgical management of a brain meningioma without severe perioperative complications.

A review of primary central nervous system neoplasms of cats

Primary central nervous system (CNS) neoplasms are uncommonly diagnosed in cats. The majority of primary feline CNS neoplasms described in the veterinary literature consist of meningioma and glioma occurring mainly in the brain and less often in the spinal cord. Although most neoplasms can be diagnosed based on routine histologic evaluation, less typical tumors need to be further characterized using immunohistochemistry. This review compiles the relevant information about the most common primary CNS neoplasms of cats available in the veterinary literature, aiming to serve as a converging source of information for the topic.

Atypically located arachnoid cyst in a five-year-old cat

Arachnoid cysts are cystic lesions that occur in spinal or intracranial locations in the leptomeningeal space. Four intracranial cases have been described in cats, three of which were diagnosed by imaging techniques alone. We now report the clinical, gross and histopathological findings in a 5-year-old, male-neutered European Shorthair cat that presented with chronic, asymmetrical encephalopathy. Using magnetic resonance imaging, a focal, fluid-filled cavity that did not show contrast enhancement was identified in the left temporal and piriform lobes. Necropsy confirmed the presence of a cystic, meningeal cavity filled with clear, serous fluid. Histologically, the cyst had an irregular, hypereosinophilic surface and single psammoma bodies with moderate perivascular oedema in the adjacent neuroparenchyma. Immunohistochemical evidence of meningeal tissue surrounding the cyst confirmed the diagnosis of an arachnoid cyst, which should be considered as a differential diagnosis of intracranial, fluid-filled cavities.

Histiocytic sarcoma with central nervous system involvement in 6 cats

Here we characterize 6 cases (4 autopsies and 2 biopsies) of histiocytic sarcoma in the CNS of cats. All affected cats had chronic, progressive clinical signs. Three autopsied cats were euthanized because of a poor prognosis, and one died. The clinical outcome for the biopsy cases remains unknown. Tumors occurred in the brain (4 cases), spinal cord (1 case), and brain and spinal cord (1 case). Neoplasms were restricted to the CNS in 3 cases. Reported gross changes in the 4 autopsy cases consisted of neuroparenchymal swelling with or without tissue pallor or gray discoloration (2 cases) and a yellow or dark-gray mass (2 cases). Histologically, pleomorphic, round-to-elongate neoplastic cells with typical histiocytic morphology effaced the neuroparenchyma and leptomeninges. Multinucleate neoplastic cells were observed in all cases. The mitotic count was 1-24 in 2.37 mm2 (10 FN22 40× fields). Neoplastic cells in all cases had positive immunolabeling for Iba1; immunolabeling was negative for E-cadherin, CD3, CD79, and MUM1, confirming their histiocytic origin.

Imaging techniques in veterinary medicine. Part II: Computed tomography, magnetic resonance imaging, nuclear medicine

Radiography and ultrasonography are the most used techniques in veterinary clinical practice, due to organizational, managerial and, mostly, economic reasons. However, in the last decades, Computed tomography (CT), Magnetic Resonance Imaging (MRI) and, to a lesser extent, Nuclear Medicine (MN) are increasingly used. As we said in the previous article, all the Diagnostic Imaging techniques are actually "indispensable" in Veterinary Medicine, where many patients do not show any symptoms.This second part describes Computed Tomography (CT), Magnetic Resonance (MRI) and Nuclear Medicine techniques in Veterinary Medicine are described.

Endoscopy-assisted resection of a sphenoid-wing meningioma using a 3D-printed patient-specific pointer in a dog: A case report

A 9-year-old female mixed-breed dog presented for treatment of a presumed sphenoid-wing meningioma. Clinical signs included tonic-clonic seizures lasting &lt;1 min, which had started 3 months previously. The physical examination results were unremarkable. An eccentrically located neoplastic cystic structure in the right sphenoid bone region suggestive of a meningioma and peritumoural brain oedema was observed in pre-operative magnetic resonance imaging (MRI). Prior to surgery, a three-dimensional (3D) patient-specific pointer (PSP) was designed using computed tomography (CT) images and computer-aided 3D design software. After a targeted approach and exposure of the lateral part of the right temporal lobe by a craniectomy guided by the 3D-PSP, complete macroscopic piecemeal resection of the meningioma could be performed using endoscopy-assisted brain surgery. Post-operative MRI confirmed complete excision of the tumor. Anticonvulsive therapy was discontinued after 90 days, and the dosage of anticonvulsants was tapered 2 weeks after surgery. At a follow-up examination 225 days post-operatively, recurrence of seizures was not observed, and the absence of tumor recurrence was confirmed by a repeat MRI examination. To the best of our knowledge, this is the first report in veterinary medicine describing a successful resection of a sphenoid-wing meningioma using a 3D-PSP. 3D-PSP-assisted craniectomy may be a surgical option for some canine skull-based tumors, such as sphenoid wing meningiomas.

Multiple Meningioma Resection by Bilateral Extended Rostrotentorial Craniotomy with a 3D-Print Guide in a Cat

Simple Summary

Meningioma is the most common intracranial neoplasia in cats. Treatments for meningiomas—including complete surgical resection, debulking, irradiation, or palliative therapy—have been reported in veterinary medicine. However, multiple meningiomas (two or more meningiomas in the same patient, separated by anatomical location) have been reported to affect the complication rate and prognosis. Moreover, the characteristics of neurosurgery—such as accurate localization and awareness of the anatomical structures of the lesions—make the surgery especially difficult for inexperienced surgeons. Surgical navigation systems have been developed, but recently, patient-specific three-dimensional(3D)-printed models and guides have also been used in orthopedics and neurosurgeries for treating many disorders with good results. A 13-year-old castrated male domestic shorthair cat was referred with multiple meningiomas located within the right frontal and occipital lobes. The cat suffered from generalized tonic–clonic seizures and mild proprioceptive ataxia. After removing both of the tumors, the cat showed a favorable clinical outcome and no neurological abnormalities throughout long-term follow-up. With a patient-specific 3D guide technology, a craniotomy for multiple meningiomas can be performed safely and accurately.

Abstract

A 13-year-old castrated male domestic shorthair cat was referred for the surgical removal of multiple meningiomas. The cat experienced generalized tonic–clonic seizures, altered mentation, mild proprioceptive ataxia, and circling. Magnetic resonance imaging (MRI) revealed two round, solitary, well-delineated, space-occupying lesions suggestive of multiple meningiomas in the right frontal and occipital lobes. Before surgery, patient-specific three-dimensional (3D) printed models and guides were produced using a 3D program based on MRI and computed tomography (CT), and a rehearsal surgery was performed. With a 3D guide to find the location of the craniotomy lines, bilateral extended rostrotentorial craniotomy allowed en bloc resection of multiple meningiomas. The bone fragment was replaced and secured to the skull with a craniofacial plate and screws with an artificial dura. All of the surgical steps were performed without complications. The preoperative presenting signs were resolved by the time of follow-up examinations 2 weeks after surgery. Twelve months after the removal of the multiple meningiomas, the cat survived without further neurological progression. For the resection of multiple meningiomas, surgery can result in large bone defects and risk of massive hemorrhage. For this challenging surgery, patient-specific 3D models and guides can be effective for accurate and safe craniotomies.

Sinonasal Meningioma in a Siberian Tiger (Panthera tigris altaica)

Simple Summary

Meningiomas are the most common primary brain tumour in dogs and cats. However, whilst there are numerous reports of meningiomas at extracranial sites in the dog (such as the spine, the eye and near the nasal cavity), in cats there have only been a few case reports of meningiomas arising in the spine, and no reports of post-mortem confirmed meningiomas arising in the eyes or near the nasal cavity. In this report, a 20-year-old captive tiger (Panthera tigris altaica) with a history of chronic eye inflammation, resulting in eventual removal of the eye, spontaneously developed epilepsy. Over the course of 2 years, the seizures worsened to the point where the animal was eventually euthanized. At autopsy, a mass was found near the nasal cavity and histological analysis showed tumour cells surrounded by a collagenous matrix. The diagnosis was sinonasal transitional meningioma. This is the first report of a captive wild felid with an extracranial meningioma, specifically a tiger with a sinonasal transitional meningioma.

Abstract

Meningiomas are the most common primary brain tumour in dogs and cats. However, whilst there are numerous reports of extracranial (spinal, orbital and sinonasal) meningiomas in the dog, there have only been a few case reports of spinal meningiomas, and no post-mortem confirmed orbital or sinonasal meningiomas in cats. In this report, a 20-year-old captive tiger (Panthera tigris altaica) with a history of chronic ocular inflammation resulting in enucleation, spontaneously developed tetanic convulsions (epileptic seizures) that over a 2-year period resulted in a gradually worsening condition and the animal was eventually euthanized. At autopsy, a focal, expansile, neoplastic mass was found in the caudal nasal cavity midline, abutting the cribriform plate and slightly compressing the calvarium. Histological analysis revealed nasal turbinates attached to a well-circumscribed expansile multi-lobular mass consisting of interlacing whorls and streams of neoplastic cells supported by a variably fibrous to microcystic collagenous matrix displaying rare psammoma bodies. The diagnosis was sinonasal transitional meningioma. This is the first report of a captive wild felid with an extracranial meningioma, specifically a tiger with a sinonasal transitional meningioma.

Cerebral meningioma associated with extensive calvarium osteolysis and presumed intratumoral carcinoma metastasis in a cat

Case summary

A 10-year-old male neutered domestic shorthair cat presented with a 3-month history of weight loss, dysorexia and lethargy. Neurological examination revealed decreased mentation, absent menace response bilaterally and proprioceptive deficits affecting all four limbs; these findings were consistent with a forebrain disorder. Brain CT revealed an extensive asymmetric permeative osteolysis destroying two-thirds of the circumference of the calvarium and involving the right frontal, parietal, temporal and occipital bones, as well as the left parietal bone. This extensive bone lysis was associated with a large ‘plaque-like’ extra-axial subdural/pachymeningeal lesion extending within the soft tissues surrounding the calvarium. The cat was humanely euthanased. Post-mortem MRI was performed, which revealed a T2-weighted (T2W) hypointense subdural lesion and a T2W hyperintense circumferential extracranial lesion lining the right calvarium and left parietal bone. Histopathological analysis on a post-mortem sample of the lesion revealed a fibroblastic subtype of meningioma. Epithelial neoplastic cells were observed scattered through the meningioma, calvarium and surrounding muscular tissues, corresponding with presumed metastatic carcinoma.

Relevance and novel information

To our knowledge, this is the first report of an intracranial meningioma associated with such an extensive and diffuse calvarial osteolysis in veterinary medicine. This is also the first description of presumed metastatic inclusions (adenocarcinoma in this case) inside an intracranial feline meningioma, which is a rare phenomenon known as tumour-to-tumour metastasis in human medicine.

Cholesterol granuloma in the choroid plexus of a cat

Background

This case report describes the clinical presentation, magnetic resonance imaging (MRI) as well as the histopathological findings in an elderly cat with an intracranial cholesterol granuloma.

Case presentation

An 11.5-year-old, male neutered cat was presented at the emergency service with deteriorating behavioral changes including aggression, and progressive generalized ataxia. Magnetic resonance imaging (MRI) of the brain revealed a large, well demarcated, inhomogeneous and contrast enhancing mass in the lateral ventricles with marked mass effect. Due to a poor clinical prognosis, the cat was euthanized. Histological examination identified the mass as a bilateral cholesterol granuloma in the choroid plexus of the lateral ventricles.

Conclusions

Although plexus cholesterol granulomas are rarely seen in cats, they should be considered as a differential diagnosis in elderly patients with neurological signs such as behavioral changes.

Standardisation of canine meningioma grading: Inter-observer agreement and recommendations for reproducible histopathologic criteria

The human grading system is currently applied to canine meningioma, although it has not been validated in dogs. The present study focused on standardising the human grading system applied to canine meningioma. Four veterinary neuropathologists graded 186 canine meningiomas as follows: Grade I tumour, with <4 mitoses/2.37 mm2 ; Grade II tumour, with ≥4 mitoses/2.37 mm2 , brain invasion or at least three of the following criteria: sheeting architecture, hypercellularity, small cells, macronucleoli, necrosis; Grade III tumour, with ≥20 mitoses/2.37 mm2 or anaplasia. Slides with grading disagreement were reviewed to define a consensus diagnosis and to assess reproducible criteria. Concordance between histologic grade and the consensus diagnosis, as well as intra- and inter-observer agreements for each criterion, were statistically analysed. Concordance between histologic grade and consensus diagnosis ranged from 59% to 100%, with lower concordance for Grade I and II tumours. The lowest inter-observer agreement was recorded for macronucleoli, small cells, hypercellularity and sheeting architecture. Tumour invasion and necrosis displayed fair agreement, while moderate agreement was reached for mitotic grade and anaplasia. The following recommendations were issued to improve the reproducibility of canine meningioma grading: (1) Assess mitotic grade in consecutive HPFs within the most mitotically active area; (2) Define invasion as neoplastic protrusions within central nervous tissue without pial lining; (3) Report spontaneous necrosis; (4) Report prominent nucleoli when visible at ×100; (5) Report pattern loss when visible at ×100 in >50% of the tumour; (6) Report necrosis, small cells, hypercellularity and macronucleoli, even when focal; (7) Report anaplasia if multifocal.

Bovine intracranial neoplasia: A retrospective case series

This case series describes the clinical and pathological findings of intracranial neoplasms in cattle, a rare entity. Data and archived tissues from 24 intracranial tumors were reviewed and investigated by immunohistochemistry for S100, glial fibrillary acidic protein, synaptophysin, pancytokeratin, vimentin, neuron-specific enolase, oligodendrocyte transcription factor 2, and isocitrate dehydrogenase 1. Ages of affected cattle ranged from 6 months to 14 years (5.7 ± 3.6 years; mean ± SD). Predominant clinical signs were altered mental state, central vestibular dysfunction, and cerebellar incoordination. Twelve gliomas, all high grade, were the most common tumors observed: oligodendrogliomas (n = 6), astrocytomas (n = 4), and undefined gliomas (n = 2). The oligodendrogliomas were located in the brainstem and extended into the ventricles, whereas all astrocytomas were located in the forebrain. Isocitrate dehydrogenase 1 gene mutation as described in humans was not detected. The 5 meningiomas exhibited microcystic, chordoid, atypical, papillary, and anaplastic subtypes. Metastatic carcinomas (n = 4) were the only secondary tumor type present, and these were located at the level of the medulla with infiltration of cranial nerves and in one case leptomeningeal carcinomatosis. In addition, 2 medulloblastomas and 1 choroid plexus carcinoma were diagnosed. Immunohistochemistry for vimentin and pancytokeratin was particularly useful to distinguish meningiomas and choroid plexus carcinoma (positive for vimentin only) from mestastatic carcinomas (positive for cytokeratin only) as all showed a papillary growth pattern. Overall, the morphological features were comparable with other species and the human and canine classifications could be applied.

Clinical presentation, diagnostic findings and outcome of dogs undergoing surgical resection for intracranial meningioma: 101 dogs

Background

Meningioma is the most common primary brain neoplasm in dogs. Further information is required regarding the expected long-term prognosis of dogs following the surgical resection of an intracranial meningioma together with the influence of adjunctive therapies. Whilst there have been several studies reporting the long-term outcome of intracranial meningioma resection following surgery alone, surgery with the use of an ultrasonic aspirator, surgery combined with radiotherapy and surgery combined with the addition of hydroxyurea, it is currently unclear which type of adjunctive therapy is associated with the most favourable outcomes. The objective of this study is to describe the presentation and outcome of dogs undergoing surgery for the resection of an intracranial meningioma and the effect of clinical factors, adjunctive therapies and meningioma histopathological subtype on the long-term outcome.

Results

A hundred and one dogs that had intracranial surgery for meningioma resection were investigated from four referral centres. 94% of dogs survived to hospital discharge with a median survival time of 386 days. Approximately 50% of dogs survived for less than a year, 25% survived between 1 and 2 years, 15% survived between 2 and 3 years and 10% survived for greater than 3 years following discharge from hospital. One or more adjunctive therapies were used in 75 dogs and the analysis of the data did not reveal a clear benefit of a specific type of adjunctive therapy. Those dogs that had a transfrontal approach had a significantly reduced survival time (MST 184 days) compared to those dogs that had a rostrotentorial approach (MST 646 days; p < 0.05). There was no association between meningioma subtype and survival time.

Conclusions

This study did not identify a clear benefit of a specific type of adjunctive therapy on the survival time. Dogs that had a transfrontal approach had a significantly reduced survival time. Intracranial surgery for meningioma resection offers an excellent prognosis for survival to discharge from hospital with a median long term survival time of 386 days.

Meningiomas in dogs

Background

Meningiomas and gliomas are the two most common types of human intracranial tumors. However, meningiomas are not exclusively human tumors and are often seen in dogs and cats.

Methods

To present meningioma surgery in dogs and compare the surgical possibilities, tumor location, and to show the differences between human and veterinary approaches to tumor profiling. Eleven dogs with meningiomas were treated surgically for 5 years. All tumors except one were resected radically (Simpson 2). Localization of tumors mirrored that of human meningiomas.

Results

Two dogs died in direct relation to surgery. One died 14 months after surgery due to tumor regrowth. Three dogs died of unrelated causes 10-36 months after tumor resection and five dogs are alive and tumor-free 2-42 months after surgery.

Conclusion

Radical surgery in dogs is as effective as in humans. Thus, we propose that it should be implemented as first-line treatment. The article is meant to please all those overly curious neurosurgeons in the world.

High-field MRI using standard pulse sequences has moderate to substantial interobserver agreement and good accuracy for differentiation between intracranial extra-axial histiocytic sarcoma and meningioma in dogs

Intracranial extra-axial histiocytic sarcoma shares common MRI features with meningioma. As histiocytic sarcoma carries a generally worse prognosis than meningioma, the ability to differentiate between these two neoplasms is of clinical value. The aim of this retrospective diagnostic accuracy and observer agreement study was to evaluate the accuracy and reliability of high-field MRI to differentiate between these two tumors, using standard pulse sequences and published MRI features. A total of 51 dogs were included (26 meningiomas and 25 histiocytic sarcomas). Magnetic resonance imaging examinations were independently assessed by three experienced board-certified radiologists, evaluating 18 imaging features. They were asked to assign each case to one of three categories (meningioma, histiocytic sarcoma, and undetermined). Agreement for the MRI diagnosis across all three reviewers was moderate (κ 0.54) while paired interobserver agreement ranged from moderate to substantial (κ 0.58-0.74) with percent agreement ranging between 86.1% and 87.7%. Overall, the probability of correctly diagnosing meningioma in a dog with this tumor ranged between 79.2% and 94.4%, and the probability of correctly diagnosing histiocytic sarcoma in a dog with this tumor ranged between 76.0% and 92.3%. The overall probability to diagnose the correct tumor, irrespective of type, ranged between 79.2% and 89.7%. Histiocytic sarcomas tended to have more extensive edema and more often had combined perilesional and distant meningeal enhancement affecting both pachy- and leptomeninges, while for meningiomas, meningeal enhancement tended to more commonly be perilesional and pachymeningeal. Imaging features that seemed more useful to make a correct diagnosis included "location/type of meningeal enhancement," "osseous changes in the adjacent neurocranium," "cystic changes," and "herniation severity."

A RETROSPECTIVE STUDY OF BRAIN LESIONS IN CAPTIVE NONDOMESTIC FELIDS

This retrospective study identified and characterized brain lesions in captive nondomestic felids from a large cat sanctuary. Necropsy reports from January 2002 through December 2018 were examined, and gross images and microscopic slides were reviewed from individual cats, where available. In total, 255 cats met the following inclusion criteria: complete necropsy report available, brain examined grossly or microscopically, and age of >1 mon. Of the 255 cats, 49 cats (19%) were determined to have brain lesions. Eleven different felid species, as well as one captive-bred hybrid (liger), were included in the study, with tigers (Panthera tigris) (55%) and lions (Panthera leo) (18%) being the most common species. Lesions were grouped into six etiologic categories: neoplastic (32%), vascular (26%), inflammatory or infectious (20%), congenital (9%), idiopathic (7%), and metabolic (6%). Not included in these categorized lesions were previously undescribed amphophilic globules in the cerebral cortex of many cats with and without other brain lesions; these were in 95% of lion and 93% of tiger brains where the cerebral cortex was available for histologic examination. These globules were not associated with clinical disease. The histopathologic and gross brain changes documented in this study provide insight into specific diseases and pathologic processes that affect the brains of captive large cat populations.

Clinical reasoning in feline vestibular syndrome: which presenting features are the most important?

OBJECTIVES

The aim of this study was to evaluate whether clinical variables from the history, clinical presentation, and physical and neurological examinations of cats with vestibular syndrome were statistically predictive of the underlying diagnosis.

METHODS

In total, 174 cats presenting with vestibular syndrome between January 2010 and May 2019 were investigated. Univariate statistical analysis of clinical variables was performed and those statistically associated with a diagnosis were retained for multivariable binary logistic regression modelling.

RESULTS

The seven most prevalent diagnoses represented 95% of vestibular presentations, which included: otitis media/interna (n = 48), idiopathic vestibular syndrome (n = 39), intracranial neoplasia (n = 24), middle ear polyp (n = 17), feline infectious peritonitis (n = 13), thiamine deficiency (n = 13) and intracranial empyema (n = 11). Idiopathic vestibular syndrome was commonly associated with non-purebred cats and had 17.8 times the odds of an improving clinical progression (95% confidence interval [CI] 1.3-250.0; P = 0.03). Intracranial neoplasia was associated with older age and chronic onset of clinical signs, and was significantly more likely to have a central vestibular neuroanatomical localisation (95% CI 8.5-344,349,142.0; P = 0.015) with postural deficits on neurological examination. Thiamine deficiency was more common in female cats, with 52.6 times the odds of a waxing and waning clinical progression (95% CI 1.2-1000; P = 0.038) and 6.8 times the odds of presenting with bilateral vestibular signs (95% CI 1.0-45.7; P = 0.047) and wide excursions of the head (95% CI 1.0-45.7; P = 0.047). Middle ear polyps were associated with 8.8 times the odds of presenting with Horner syndrome (95% CI 1.5-50.0; P = 0.015).

CONCLUSIONS AND RELEVANCE

Although it may be difficult to identify the underlying diagnosis in cats with vestibular syndrome from the presenting features alone, there are instances in which discrete clinical features may help to guide clinical reasoning when evaluating cats with vestibular presentations.

Pathological and immunohistochemical features of 45 cases of feline meningioma

Meningioma is the most common primary brain tumor in cats, although there are few reports about their pathological features. To investigate the histopathological subtypes and immunohistochemical features including expression of cytokeratin and cell adhesion molecules, 45 cases of feline meningioma were examined. The mean age was 12.5 years (range 6–21 years). No statistically significant sex predilection was observed. Regarding the anatomical location of meningioma, tumors mostly developed in the cerebrum, followed by spinal cord and cerebellum, and multiple meningioma was observed in one cat. Microscopically, linear or focal mineralization was observed in 40 cases and cholesterol cleft was observed in 14 cases. Based on histopathological subtypes, there were 15 fibrous, 22 transitional, 2 meningothelial, 5 atypical, and 1 anaplastic meningiomas. These subtypes are classified into grade 1 (39 cases), grade 2 (5 cases), and grade 3 (1 case). There was no significant difference in the Ki-67 index among histological subtypes or grades. Immunohistochemically, the tumor cells were positive for cytokeratin in 5 cases (12.8%), vimentin in 17 cases (43.6%), E-cadherin in 36 cases (92.3%), β-catenin in 21 cases (53.8%), and N-cadherin in 1 case (2.6%), demonstrating the utility of E-cadherin-immunohistochemistry for the diagnosis of feline meningiomas.

Subcutaneous seeding following surgical excision of an intracranial meningioma in a cat

Traditionally patient owners express their concerns that surgical or diagnostic procedures on a tumor may induce metastasis. In pets, this has been documented in only very rare occasions, e. g. needle path metastases after diagnostic fine needle biopsies of urinary bladder or prostatic tumors. Here, we describe a case of subcutaneous seeding of a feline intracranial grade 1 meningioma 6 months after surgical resection. A 10-year-old male neutered domestic shorthaired cat with typical neurological signs was diagnosed with an extra-axial contrast enhancing mass in the dorsal frontotemporal lobes using magnetic resonance imaging (MRI). Transfronto-parietal bone craniotomy was performed and the 24 × 19 × 22 mm large tumor was largely removed. Tumor recurrence after 12 months resulted in a second surgical tumor removal. In addition, 2 subcutaneous masses of 10 × 4 × 4 mm in size were removed at the site of the original surgical site which were fully separated from the recurring meningeal tumor by the intact frontal bone. Histology and immunohistochemistry suggested the same tumor growth in all 4 masses. Most likely the tumor seeding had been caused during the first surgery. After all, the risk of surgical seeding of a benign tumor seems very low.

Comparison of Canine and Feline Meningiomas Using the Apparent Diffusion Coefficient and Fractional Anisotropy

Meningiomas are the most common intracranial tumor in dogs and cats, and their surgical resection is often performed because they are present on the brain surface. Typical meningiomas show comparatively characteristic magnetic resonance imaging findings that lead to clinical diagnosis; however, it is necessary to capture not only macroscopic changes but also microstructural changes to devise a strategy for surgical resection and/or quality of removal. To visualize such microstructural changes, diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) have been used in human medicine. The aim of this retrospective study was to investigate the different characteristics of the apparent diffusion coefficient (ADC) from DWI and fractional anisotropy (FA) from DTI of meningioma between dogs and cats. Statistical analyses were performed to compare ADC and FA values between the intratumoral or peritumoral regions and normal-appearing white matter (NAWM) among 13 dogs (13 lesions, but 12 each in ADC and FA analysis) and six cats (seven lesions). The NAWM of cats had a significantly lower ADC and higher FA compared to dogs. Therefore, for a comparison between dogs and cats, we used ADC and FA ratios that were calculated by dividing the subject (intra- or peritumoral) ADC and FA values by those of NAWM on the contralateral side. Regarding the intratumoral region, feline meningiomas showed a significantly lower ADC ratio and higher FA ratio than canine meningiomas. This study suggested that ADC and FA may be able to distinguish a meningioma that is solid and easy to detach, like as typical feline meningiomas.

Incidence and type of brain herniation associated with intracranial meningioma in dogs and cats

The incidence of brain herniation (BH) in association with intracranial meningioma (ICM) in dogs and cats is poorly described. The aim of this study was to evaluate the rate and type of brain herniations in client-owned dogs and cats with ICMs and to determine the meningioma volume (MV) relative to cranial cavity volume (CCV). A retrospective magnetic resonance imaging (MRI) analysis study of 24 cats and 45 dogs with ICMs was conducted to ascertain the presence and characteristics of BH. MV and CCV were measured and their ratio was calculated for each animal. Correlations of MV/CCV with independent variables were analyzed. BH was encountered in 24/24 cats (100%) and 30/45 dogs (66.7%) with ICMs. In cats, the most frequent presentation was foramenal herniation (FMH; 23/24, 95.8%), followed by caudotentorial (CTH; 21/24, 87.5%) and subfalcine (SH; 18/24, 75.0%) herniation. In dogs, the most frequent presentation was SH (28/45; 62.2%), followed by CTH (9/45; 20%) and FMH (2/45; 4.4%). Relative to dogs, cats with ICM had greater incidences of FMH (P<0.001) and CTH (P<0.001). Mean MV/CCV ratio was higher in cats (0.098) than in dogs (0.038; P<0.001). The most common clinical sign of ICM was altered behavior in cats (43%, P<0.01) and seizures in dogs (74.4%, P<0.001). In conclusion, cats were found to be more likely than dogs to present FMH and CTH, with a proportionally greater neoplasia volume.

Surgical treatment of rostrotentorial meningioma complicated by foraminal herniation in the cat

OBJECTIVES

This study was performed to evaluate retrospectively the clinical signs, complications and postoperative outcomes of feline intracranial meningioma (IM) with concurrent cingulate, transtentorial and foramen magnum herniations.

METHODS

The medical records and MRI scans of cats with IM and cerebral herniation were reviewed. Cases involving concurrent cingulate, transtentorial and foramen magnum herniations were included. Owners were contacted to obtain long-term follow-up information.

RESULTS

Seven cats (four castrated males and three spayed females) met the inclusion criteria. Median age was 13.0 years (range 9.9-16.1 years) and median duration of clinical signs was 35 days (range 21-163 days). The clinical signs of cats with cerebral herniation included visual impairment (n = 5 [71.4%]), ataxia (n = 4 [57.1%]), impaired consciousness (n = 2 [28.6%]), head pressing (n = 2 [28.6%]), paresis (n = 1 [14.3%]), torticollis (n = 1 [14.3%]) and personality changes (n = 1 [14.3%]). Median tumour volume, cranial cavity volume and tumour volume:intracranial volume ratio before surgery were 3.37 cm3 (range 3.23-11.5 cm3), 32.6 cm3 (range 29.8-78.3 cm3) and 10.4% (range 5.3-35.3%), respectively. Median overall tumour excision rate was 90.6%. Preoperative intracranial pressure (ICP) ranged from 15 to 32 mmHg (median 29 mmHg). In all cases, the ICP dropped to 0 mmHg immediately after tumour removal. No adjuvant therapy was required after surgery. The median survival period was 612 days (range 55-1453 days).

CONCLUSIONS AND RELEVANCE

The results of this study indicate that surgical treatment of rostrotentorial IM is effective and allows prolonged survival, even in cats with concurrent cingulate, transtentorial and foramen magnum herniations.

Formation of a meningoencephalocele after removal of a frontal lobe meningioma by transfrontal craniotomy in a cat

Case summary

A 10-year-old castrated male domestic shorthair cat was referred for surgical treatment of a left-sided frontal lobe meningioma diagnosed by CT. Clinically, the cat had generalised tonic–clonic seizures, which reduced in frequency after treatment was started with prednisolone. After definition of the anatomical landmarks of the feline skull, a bilateral transfrontal craniotomy allowed en bloc removal of the meningioma. While postoperative recovery was uneventful, right-sided proprioceptive deficits were still present 6 months after surgery. MRI detected a probable meningoencephalocele herniating through the surgical bone defect in the frontal sinus. Because of the mild neurological deficits and good quality of life, the meningoencephalocele was not treated. Thirty-one months after meningioma removal the cat was alive without further neurological progression.

Relevance and novel information

To our knowledge, this is the first report to describe, in detail, the technique of transfrontal craniotomy in cats. Iatrogenic meningoencephalocele is a complication that has not previously been described after meningioma removal in cats, and should be considered as a potential complication after craniotomy.

Immunoexpression of epithelial membrane antigen in canine meningioma: Novel results for perspective considerations

Epithelial membrane antigen (EMA) is one of the most widely used diagnostic immunohistochemical markers for human meningioma. To date, no published study on EMA expression in formalin-fixed paraffin-embedded (FFPE) tissue samples of canine meningioma is available. Here, we describe the results of an immunohistochemical study on 25 FFPE canine meningiomas using a monoclonal anti-human EMA antibody. All meningiomas showed positive staining for EMA with cytoplasmic pattern, in nine cases associated with membranous staining. Area and intensity of staining were highly variable among cases. No clear relationships between tumour subtype/grade and area/intensity of staining were found. However, epithelial-like patterns showed a higher affinity for EMA compared to the mesenchymal one. The present study provides the basis to explore the potential diagnostic application of this marker in canine meningioma. To investigate EMA expression in other central nervous system tumours of dogs are necessary to assess the specificity of this marker.

Meningioma and associated cerebral infarction in three dogs

Background

In dogs, meningiomas mostly cause chronic progressive clinical signs due to slow tumor growth.

Case presentation

In contrast, three dogs were presented with the history of chronic generalized tonic-clonic seizures and peracute deterioration with sudden onset of neurological deficits in accordance with an extensive unilateral forebrain lesion. Magnetic resonance imaging examinations of the dogs revealed a well-delineated extraaxial T2W hyperintense mass in the rostral forebrain with homogeneous contrast enhancement. Additionally, an intraaxial, well-demarcated, unilateral lesion was apparent in the parenchyma supplied by the middle cerebral artery. In two cases, necropsy revealed meningothelial meningioma in the rostral fossa and marked eosinophilic neuronal necrosis, a sign of ischemia, focal malacia, edema and gliosis in the temporal lobe and hippocampus because of a focal thrombosis of the middle cerebral artery. In the third case symptomatic treatment resulted in improvement of clinical signs enabling a good quality of life for the patient.

Conclusions

In dogs with structural epilepsy caused by meningioma, acute deterioration of clinical signs can be associated with ischemic infarctions as a potential complication.

Efficacy of frameless stereotactic radiotherapy for the treatment of presumptive canine intracranial gliomas: A retrospective analysis (2014-2017)

The use of conventional multi-fractionated radiotherapy for the treatment of glial tumours is well documented in the literature. Recently, stereotactic radiotherapy (SRT) has become more widely available allowing for hypo-fractionated protocols; however, its usefulness in the treatment of canine intracranial gliomas is largely undetermined. We conducted a retrospective analysis, including 21 dogs diagnosed with presumptive intracranial gliomas treated with one or more courses of three fractions of 8 to 10 Gy CyberKnife SRT. The objective of this study was to evaluate the efficacy, safety and prognostic factors associated with the use of SRT for the treatment of canine intracranial gliomas. Overall MST for all dogs was 636 days (d). Dogs treated with one course of the described SRT protocol had a MST of 258 days while those treated with >1 course had a MST of 865 days (P = .0077 log rank, 0.0139 Wilcoxon). Dogs treated with one course of SRT who received adjuvant chemotherapy had a MST of >658 days and lived significantly longer than those who did not receive chemotherapy (MST, 230 days) (P = .0414 log rank, 0.0453 Wilcoxon). The most common adverse event included presumptive transient demyelination in 3/21 dogs, which was treated successfully with corticosteroids in all patients. This study provides evidence that SRT is effective in prolonging survival in dogs with intracranial gliomas, and may provide similar results to conventional fractionated protocols, while decreasing the number of hospital visits and anaesthetic episodes. Additionally, it appears that patients can be safely treated with multiple rounds of SRT resulting in improved survival times.

Safety, Tumor Reduction, and Clinical Impact of Zika Virus Injection in Dogs with Advanced-Stage Brain Tumors

Malignant brain tumors are among the most aggressive cancers with poor prognosis and no effective treatment. Recently, we reported the oncolytic potential of Zika virus infecting and destroying the human central nervous system (CNS) tumors in vitro and in immunodeficient mice model. However, translating this approach to humans requires pre-clinical trials in another immunocompetent animal model. Here, we analyzed the safety of Brazilian Zika virus (ZIKV^BR) intrathecal injections in three dogs bearing spontaneous CNS tumors aiming an anti-tumoral therapy. We further assessed some aspects of the innate immune and inflammatory response that triggers the anti-tumoral response observed during the ZIKV^BR administration in vivo and in vitro. For the first time, we showed that there were no negative clinical side effects following ZIKV^BR CNS injections in dogs, confirming the safety of the procedure. Furthermore, the intrathecal ZIKV^BR injections reduced tumor size in immunocompetent dogs bearing spontaneous intracranial tumors, improved their neurological clinical symptoms significantly, and extended their survival by inducing the destruction specifically of tumor cells, sparing normal neurons, and activating an immune response. These results open new perspectives for upcoming virotherapy using ZIKV to destroy and induce an anti-tumoral immune response in CNS tumors for which there are currently no effective treatments.

The Pathophysiology of Dying

The pathophysiology of dying and death, related to veterinary patients, has warranted less attention than normal and abnormal physiologic processes related to life preservation. In addition, many veterinary patients are euthanized, which prevents observation of natural disease progression, while ameliorating suffering. Acute death in human medicine can serve as a model for understanding mechanisms of death in veterinary patients under certain conditions. The specific cause of cardiac arrest in several different models of disease elucidates end-stage disease processes. Understanding the path to death and dying in veterinary patients physiologically serves to guide best practices focused on alleviating suffering.

Companion animal models of neurological disease

Clinical translation of novel therapeutics that improve the survival and quality of life of patients with neurological disease remains a challenge, with many investigational drug and device candidates failing in advanced stage clinical trials. Naturally occurring inherited and acquired neurological diseases, such as epilepsy, inborn errors of metabolism, brain tumors, spinal cord injury, and stroke occur frequently in companion animals, and many of these share epidemiologic, pathophysiologic and clinical features with their human counterparts. As companion animals have a relatively abbreviated lifespan and genetic background, are immunocompetent, share their environment with human caregivers, and can be clinically managed using techniques and tools similar to those used in humans, they have tremendous potential for increasing the predictive value of preclinical drug and device studies. Here, we review comparative features of spontaneous neurological diseases in companion animals with an emphasis on neuroimaging methods and features, illustrate their historical use in translational studies, and discuss inherent limitations associated with each disease model. Integration of companion animals with naturally occurring disease into preclinical studies can complement and expand the knowledge gained from studies in other animal models, accelerate or improve the manner in which research is translated to the human clinic, and ultimately generate discoveries that will benefit the health of humans and animals.

A retrospective survey on canine intracranial tumors between 2007 and 2017

To clarify the prevalence of canine intracranial tumors in Japan, a retrospective study was performed using data on 186 canine intracranial tumors. Of 186 cases, 159 cases (85.5%) were primary and 27 cases (14.5%) were secondary intracranial tumors. Among primary intracranial tumors, meningioma (50.9%) was the most common, followed by glial tumors (21.4%) and primary intracranial histiocytic sarcoma (12.6%). These 3 tumors were most frequently found in middle-aged to elderly dogs without any sex predilection. Regarding glial tumors, the incidence of oligodendroglial tumors (79.4%) was higher than that of astrocytic tumors (17.6%). A significant breed predisposition (P<0.05) was observed for meningioma in Rough Collie, Golden Retriever, Miniature Schnauzer, and Scottish Terrier; for glial tumors in Bouvier de Flandres, French Bulldog, Newfoundland, Bulldog, and Boxer; for primary intracranial histiocytic sarcoma in Pembroke Welsh Corgi, Siberian Husky, and Miniature Schnauzer. The high incidence of oligodendroglial tumors in dogs and the breed predisposition for primary intracranial histiocytic sarcoma in Pembroke Welsh Corgi have not been reported in previous epidemiological studies on canine tumors. Since the incidence of intracranial tumors was vary among dog breeds, the present results demonstrate the uniqueness of the canine breed population in Japan.

Microtubule-Associated Protein 2 Expression in Canine Glioma

Canine glioma is considered a potential model for human glioma, with recent studies of occurrence, therapy, and reclassification supporting the value of the canine model. The current diagnosis of canine glioma is based on morphologic criteria and immunohistochemistry (IHC), including oligodendrocyte transcription factor 2 (Olig2), glial fibrillary acidic protein (GFAP), and 2′, 3′ cyclic nucleotide phosphatase (CNPase). Microtubule-associated protein 2 (MAP2) is a proven marker of human glioma and is used to complement the diagnosis and its specific immunoreactivity pattern contributes to the differentiation of astrocytomas from other glial tumors. The objective of this study was to evaluate whether canine gliomas express MAP2 and to explore differences in the pattern of immunolabeling between different gliomas. Seventy-eight cases of canine glioma were evaluated for MAP2 expression by immunohistochemistry. A glial origin was supported by Olig2 IHC in all cases. MAP2 immunolabeling was evaluated on a semi-quantitative basis, including the percentage of immunolabeled neoplastic cells, as well as the signal intensity, distribution, and pattern of immunolabeling. MAP2 was expressed in all cases, with significant correlation between diagnosis and signal intensity (P = 0.04). MAP2 immunolabeling distribution was dominated by diffuse (34/78; 44%), followed by patchy (20/78; 26%), multifocal to coalescing (16/78; 21%), and scattered (8/78; 10%). All oligodendrogliomas (53/53; 100%) and undefined gliomas (12/12; 100%) revealed a combination of perinuclear and cytoplasmic immunolabeling, and all but 3 astrocytomas had a combination of perinuclear and cytoplasmic processes immunolabeling (10/13; 77%). Significant correlation between immunolabeling pattern and diagnosis was obtained (P = 0.001). The study demonstrates that MAP2 is expressed in canine gliomas and the pattern of expression can also be applied to help distinguish astrocytomas from oligodendrogliomas and undefined gliomas.

Atypical and malignant canine intracranial meningiomas may have lower apparent diffusion coefficient values than benign tumors

Canine intracranial meningiomas can be graded based on histological classification as benign (grade I), atypical (grade II), and anaplastic or malignant (grade III). In people, grade II/III meningiomas behave more aggressively, have a higher potential for recurrence after surgical resection, and have lower apparent diffusion coefficient (ADC) values with diffusion weighted imaging (DWI). In this retrospective analytical cross-sectional study, 42 dogs had ADC values quantified in an attempt to differentiate tumor histologic grade. Our hypothesis was that ADC values would be significantly lower in grade II and III versus grade I meningiomas in dogs. On each ADC image, a polygonal region of interest (ROI) was hand-drawn along the lesion's periphery, excluding fluid-filled and hemorrhagic regions. Mean ADC value (ADC_mean ) and minimum ADC value (ADC_min ) were calculated. Additionally, two smaller, ovoid ROI were drawn within the lesion with mean ADC calculated (ADC_{mean sR} and ADC_{min sR} ). Normalized ADC values using white matter were also calculated (ADC_n and ADC_{n sR} ). Grades of each tumor were assigned based on histopathology review. Association between ADC parameters and histological grade was tested by means of two-sample t-tests. There were 14 grade I (33.3%), 25 grade II (59.5%), and three grade III (7.2%) meningiomas. ADC_{mean sR} and ADC_{min sR} were significantly lower when comparing grade II/III to grade I (P < .05). Grade II tumors had significantly lower ADC_mean , ADC_{mean sR} , ADC_{min sR} , ADC_n , and ADC_{n sR} than grade I meningiomas. This preliminary study supports the potential of ADC values to help predict the histological grade of intracranial meningiomas in dogs.

Using biologically based objectives to optimize boost intensity-modulated radiation therapy planning for brainstem tumors in dogs

Irradiated brain tumors commonly progress at the primary site, generating interest in focal dose escalation. The aim of this retrospective observational study was to use biological optimization objectives for a modeling exercise with simultaneously‐integrated boost IMRT (SIB‐IMRT) to generate a dose‐escalated protocol with acceptable late radiation toxicity risk estimate and improve tumor control for brainstem tumors in dogs safely. We re‐planned 20 dog brainstem tumor datasets with SIB‐IMRT, prescribing 20 × 2.81 Gy to the gross tumor volume (GTV) and 20 × 2.5 Gy to the planning target volume. During the optimization process, we used biologically equivalent generalized equivalent uniform doses (gEUD) as planning aids. These were derived from human data, calculated to adhere to normal tissue complication probability (NTCP) ≤5%, and converted to the herein used fractionation schedule. We extracted the absolute organ at risk dose‐volume histograms to calculate NTCP of each individual plan. For planning optimization, gEUD_{(a = 4)} = 39.8 Gy for brain and gEUD_{(a = 6.3)} = 43.8 Gy for brainstem were applied. Mean brain NTCP was low with 0.43% (SD ±0.49%, range 0.01‐2.04%); mean brainstem NTCP was higher with 7.18% (SD ±4.29%, range 2.87‐20.72%). Nevertheless, NTCP of < 10% in brainstem was achievable in 80% (16/20) of dogs. Spearman's correlation between relative GTV and NTCP was high (ρ = 0.798, P < .001), emphasizing increased risk with relative size even with subvolume‐boost. Including biologically based gEUD values into optimization allowed estimating NTCP during the planning process. In conclusion, gEUD‐based SIB‐IMRT planning resulted in dose‐escalated treatment plans with acceptable risk estimate of NTCP < 10% in the majority of dogs with brainstem tumors. Risk was correlated with relative tumor size.

Incidence of and risk factors for major complications or death in dogs undergoing cytoreductive surgery for treatment of suspected primary intracranial masses

OBJECTIVE To determine incidence of and risk factors for major complications occurring in dogs within 30 days after cytoreductive surgery performed by a single pair of surgeons for treatment of suspected primary intracranial masses. DESIGN Retrospective cohort study. ANIMALS 160 client-owned dogs that underwent cytoreductive surgery for treatment of suspected primary intracranial masses between January 2009 and December 2015 at a veterinary teaching hospital. PROCEDURES Medical records were retrospectively reviewed for complications occurring within 30 days after surgery. Data (eg, signalment, clinical signs, previous treatments, preoperative neurologic examination findings, neuroanatomical location, time from onset of clinical signs to surgery, surgical approach, and histopathologic diagnosis) were analyzed for associations with death and with development of major complications other than death. RESULTS 21 (13.1%) dogs died (11 during hospitalization and 10 after discharge) and 30 (18.8%) developed major complications other than death during the first 30 days after surgery. Dogs with abnormal preoperative neurologic examination findings were more likely to develop complications or die. Dogs undergoing a suboccipital approach were more likely to die. The most common postoperative complications other than death were seizures (n = 18 [11.3%]), worsening of neurologic status (6 [3.8%]), and aspiration pneumonia (6 [3.8%]). CONCLUSIONS AND CLINICAL RELEVANCE Results of the present study provided valuable information on predisposing factors, odds of major complications or death, and incidences of major complications or death in dogs during the first 30 days after undergoing cytoreductive surgery for treatment of suspected primary intracranial masses. Careful case selection may help improve outcomes and minimize complications.