Characteristics and Survival of 121 Cats Undergoing Excision of Intracranial Meningiomas (1994-2011)

Meningioma in the fourth ventricle in 2 cats

Feline meningiomas typically arise on the surface of the brain but can occur in the third ventricle. Meningiomas in the fourth ventricle have not been reported in cats, to our knowledge. Here, we describe the clinical and pathologic findings of meningioma in the fourth ventricle in 2 cats. Both affected patients (1 castrated male, 1 spayed female) were 15-y-old. Case 2 had neurologic signs, including absent menace response, head tilt, and ataxia. Grossly, both tumors were well-demarcated and firm, expanded the fourth ventricle, and compressed the adjacent neuroparenchyma. Cytology of the ventricular mass in case 1 revealed a spindle-cell neoplasm. Based on histology, the neoplasms were classified as WHO grade 1 fibrous meningioma (case 1) and transitional meningioma (case 2). Immunohistochemistry revealed diffuse, robust cytoplasmic E-cadherin and vimentin immunolabeling in both cases and multifocal, weak cytoplasmic pan-cytokeratin AE1/AE3 immunolabeling in case 2. Our findings indicate that meningiomas should be included as a differential diagnosis for tumors of the fourth ventricle in cats.

Introduction and Summary of Diagnosis and Treatment of Brain Tumors in Dogs and Cats

Meningiomas are the most common tumor type in the brain in dogs and cats, and survival times are much higher for cats than dogs. Glioma is much more common in the dog, and median survival time is poor without definitive therapy. No recommendations currently exist for treatment of glioma in dogs, and there is ongoing research as the dog is a valid spontaneous model for the human equivalent disease. Other intracranial tumor types like lymphoma and histiocytic sarcoma do occur, though at a much lower frequency.

Radiation Therapy for Brain Tumors in Dogs and Cats

External beam radiation therapy (RT) has become the standard of care for non-resectable or post-operative incompletely excised brain tumors in dogs and cats due to its relatively low side effect profile and increasing availability. This article reviews the indications for, expected outcomes of and possible toxicities associated with RT, follow-up care recommendations after RT, and publications about specific tumor types in dogs and cats with brain tumors.

Immunohistochemical Staining Properties of Osteopontin and Ki-67 in Feline Meningiomas

The high recurrence rate of feline meningioma despite the generally benign histomorphology warrants additional markers of clinical aggressiveness. The Ki-67 index is commonly used as prognostic marker for meningioma recurrence in people. Osteopontin (OPN) is a protein involved in tumor progression and may be a potential malignancy marker. To date, osteopontin expression has not been investigated in feline meningioma. The aim of this study was to evaluate the extent of Ki-67 and osteopontin immunostaining of feline meningioma and to find possible associations with WHO (World Health Organization) grades and subtypes. Fifty-three feline meningioma samples were graded according to the human WHO classification and underwent immunohistochemical examination for Ki-67 and OPN. Fifty samples were classified as WHO grade I and three as WHO grade II. The mean Ki-67 ratio was 9.19 ± 9.47. Osteopontin expression was correspondingly high with a mean OPN IHC score of 150.17 (0-242.8), and a median Allred score of 7 (0-8). There was no significant correlation with Ki-67 index, osteopontin expression, WHO grades, or subtypes. The overall high expressions of osteopontin and Ki-67 may help explain the tendency for recurrence of feline meningioma. The human WHO grading system may not be sufficient to accurately estimate the clinical behavior of meningioma in this species.

Brain invasion by an otherwise benign meningioma in a cat

Case summary

A 13-year-old castrated male American Shorthair cat was referred for evaluation following a 3-week history of poor balance and decreased activity. The MRI findings revealed a well-defined left caudal cerebellar mass with a diameter of 1.2 cm, consistent with a meningioma. CT and MRI scans did not reveal metastasis. After a suboccipital craniotomy, the mass was resected subtotally as a result of parenchymal invasion. A histopathological examination revealed a benign fibrous meningioma with invasion into the cerebellum at the tumour margins. Postoperatively, the cat remained asymptomatic for 25 months, but ataxia recurred, and tumour recurrence was confirmed using MRI and post-mortem examination.

Relevance and novel information

This case demonstrates that even feline meningiomas with benign features can exhibit brain invasion. Since brain invasion is an indicator of malignancy in meningioma, a detailed histopathological evaluation of the tumour margins is essential for accurate grading and prognosis.

Magnetic resonance and computed tomographic imaging characteristics and potential molecular mechanisms of feline meningioma associated calvarial hyperostosis

Meningiomas are the most common feline primary brain tumours, and calvarial hyperostosis (CH) is frequently documented in association with this neoplastic entity. The clinical significance of and mechanisms driving the formation of CH in cats with meningiomas are poorly understood, although tumour invasion into the skull and tumour production of cytokines and enzymes have been implicated as causes of CH in humans. This retrospective study investigated relationships between signalment, MRI or CT imaging features, histopathologic tumour characteristics, alkaline phosphatase (ALP) isoenzyme concentrations, tumour expression of matrix metalloproteinases (MMP)-2, MMP-9, and interleukin-6 (IL-6), and progression free survival times (PFS) following surgical treatment in 27 cats with meningiomas with (n = 15) or without (n = 12) evidence of CH. No significant differences in breed, age, sex, body weight, tumour grade, tumour volume, peritumoral edema burden, ALP isoenzyme concentrations, tumour Ki-67 labelling indices or MMP-2 or MMP-9 expression and activity, or PFS were noted between cats with or without CH. There was a trend towards higher serum (p = .06) and intratumoral (p = .07) concentrations of IL-6 in cats with CH, but these comparisons were not statistically significant. Histologic evidence of tumour invasion into bone was observed in 5/12 (42%) with CH and in no (0/6) cats without CH, although this was not statistically significant (p = .07). Tumour invasion into bone and tumour production of IL-6 may contribute to the formation of meningioma associated CH in cats, although larger studies are required to further substantiate these findings and determine their clinical relevance.

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.

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.

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.

Epithelial membrane antigen-reactive feline chordoid meningioma in a European wildcat (Felis silvestris)

Meningioma is the most frequent intracranial neoplasm in cats. Here we describe the first case of chordoid meningioma (CM), a rare grade II meningioma subtype, in a 5.5-year-old European wildcat (Felis silvestris) from a Swiss zoo. The wildcat was found dead after a clinical history of neurological signs and clinical suspicion of a carcinoma in the right external ear canal with concurrent chronic otitis. Post-mortem examination revealed a large intracranial, extra-axial and intradural neoplasm that invaded into the right ear canal and had histological features compatible with CM, which has been only reported in humans and dogs. Neoplastic cells expressed vimentin but were negative for glial fibrillary acidic protein, S100 and pancytokeratin. Immunohistochemistry revealed epithelial membrane antigen (EMA) expression in neoplastic cells. To the best of our knowledge, we provide the first evidence of EMA expression in feline meningioma.

Neurosurgery in feline epilepsy, including clinicopathology of feline epilepsy syndromes

Feline epilepsy is treated with antiseizure medications, which achieves fair to good seizure control. However, a small subset of feline patients with drug-resistant epilepsy requires alternative therapies. Furthermore, approximately 50 % of cats with epileptic seizures are diagnosed with structural epilepsy with or without hippocampal abnormality and may respond to surgical intervention. The presence of hippocampal pathology and intracranial tumors is a key point to consider for surgical treatment. This review describes feline epilepsy syndrome and epilepsy-related pathology, and discusses the indications for and availability of neurosurgery, including lesionectomy, temporal lobectomy with hippocampectomy, and corpus callosotomy, for cats with different epilepsy types.

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.

Indications, complications, and mortality rate following craniotomy or craniectomy in dogs and cats: 165 cases (1995-2016)

OBJECTIVE

To determine the most common indications for cranial surgery and identify risk factors associated with the occurrence of complications and death in the perioperative period following cranial surgery.

ANIMALS

150 dogs and 15 cats.

PROCEDURES

For this multi-institutional retrospective case series, medical records of dogs and cats that underwent cranial surgery at any of the 4 participating institutions between 1995 and 2016 were reviewed. Variables were evaluated included species, sex, age, neurolocalization, history of preoperative seizures, surgical approach, histological results, perioperative complications, and outcome. Logistic regression analysis was performed to assess for risk factors for complications.

RESULTS

The most common neurolocalization was the forebrain (110/165 [66.7%]), with 94 (57.0%) animals having had seizures preoperatively. The rostrotentorial (116/165 [70.3%]) and caudotentorial (32/165 [19.4%]) surgical approaches were most commonly reported. The most common indication was the treatment of meningioma (75/142 [52.8%]). Complications arose in 58 of the 165 (35.2%) cases within 24 hours and in 86 (52.1%) cases 1 to 10 days postoperatively. Perioperative complications included hypotension (38/165 [23.0%]) and anemia (27/165 [16.4%]). During the postoperative period, the most common complications were neurologic deficits, seizures, postoperative anemia, and aspiration pneumonia. The mortality rate with death or euthanasia perioperatively or ≤ 10 days postoperatively was 14.5% (24/165). Long-term complications occurred in 65 of the 165 (39.4%) animals, with seizures and neurologic deficits being the most common.

CLINICAL RELEVANCE

Cranial surgery was performed most commonly for the removal of neoplastic lesions in dogs and cats, and most complications were not life-threatening.

Case Report: Ventriculoperitoneal Shunting and Radiation Therapy Treatment in a Cat With a Suspected Choroid Plexus Tumor and Hypertensive Hydrocephalus

A 14-year-old male neutered domestic short-hair cat was presented for a history of behavioral changes and episodes of urinary retention. Neurological examination was consistent with a multifocal intracranial neuroanatomical localization, with suspected right sided lateralisation and suspected raised intracranial pressure (ICP). Brain magnetic resonance imaging (MRI) revealed an intraventricular multilobulated well-defined T2W-hyperintense and T1W-isointense, markedly contrast enhancing mass lesion within the dorsal aspect of the III ventricle extending into the left lateral ventricle, causing hypertensive obstructive hydrocephalus. A ventriculoperitoneal shunt (VPS) was placed within the left lateral ventricle, followed by a radiation therapy (RT) course of 45 Gy total dose in 18 daily fractions. Six-months post-RT, computed tomography revealed mild reduction in mass size and resolution of the hydrocephalus. The patient was neurologically normal with no medical treatment. Raised ICP causes severe clinical signs, can lead to brain ischaemia and herniation, and significantly increases anesthetic risk during RT. Placement of a VPS in cats with hypertensive obstructive hydrocephalus may allow improvement of neurological signs due to raised ICP, and therefore making the patient a more stable candidate for anesthesia and radiation therapy.

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.

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.

Case Report: Long-Term Chemotherapy With Hydroxyurea and Prednisolone in a Cat With a Meningioma: Correlation of FDG Uptake and Tumor Grade Assessed by Histopathology and Expression of Ki-67 and p53

A 15.5-year-old, neutered, male, domestic shorthair cat was presented with neurologic dysfunctions. At presentation, an obtunded mental status and vestibular ataxia were identified. On neurologic examination, postural reactions were decreased-to-absent in all four limbs, and pupillary light reflexes showed bilaterally delayed results. Magnetic resonance imaging was performed, and a demarcated lesion was identified in the third ventricle. The cat was tentatively diagnosed with a brain tumor, which was suspected to be a meningioma. The cat was treated with hydroxyurea and prednisolone. Mental status was considered more alert, and ataxia improved following treatment. On the 106th day after the commencement of treatment, a ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan was performed. On the PET images, a hypermetabolic region was found in the lesion. The average standardized uptake value of FDG was 2.47, and the tumor-to-normal-tissue ratio was 1.25. The cat died 408 days following the commencement of treatment, and a grade 1 meningioma was confirmed by postmortem histopathology. Immunohistochemistry for Ki-67 and p53 was performed. The labeling indices of Ki-67 and p53 were 2.56 and 0%, respectively. This case shows that chemotherapy with hydroxyurea and prednisolone may be considered in the treatment of feline meningiomas. Furthermore, this is the first case describing the application of FDG-PET to visualize a naturally occurring meningioma in a cat.

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.

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.

Radiation therapy for intracranial tumours in cats with neurological signs

OBJECTIVES

The aim of this study was to evaluate the outcome of cats with intracranial tumours presenting with neurological signs treated with radiation therapy.

METHODS

This study comprised a retrospective multicentre case series. Medical records of a total of 22 cats with intracranial space-occupying lesions, presenting with neurological signs and/or epileptic seizures and treated with external beam radiation therapy, were reviewed. In the treated cats, patient-, tumour- and treatment-related variables were investigated, including age, sex, tumour location, tumour volume, total radiation dose, equivalent dose in 2 Gy fractions (EQD2), corticosteroid dose, overall treatment time and institution for influence on local tumour control and survival.

RESULTS

Based on advanced imaging characteristics, the 22 treated cats presented with meningioma (n = 11), pituitary tumour (n = 8), choroid plexus tumour (n = 2) or glioma (n = 1). Allocated to the neuraxis, 11 lesions were extra-axial, three were intra-axial and eight were located in the pituitary region. At diagnosis, 21 cats exhibited altered neurological status. One cat presented with epileptic seizures and another cat had both seizures and altered neurological status. The mean total physical dose of radiation was 41.63 Gy (± 4.33), range 24-45 Gy. In all but one cat (95.5%), neurological signs improved after radiation therapy. The median progression-free survival was 510 days (95% confidence interval [CI]: 51-969). The proportion free of progression at 1 year was 55.7% (95% CI: 33-78). Fourteen cats died (only in five cases was death related to the intracranial tumour) and eight cats were still alive or lost to follow-up. The median overall survival time was 515 days (95% CI: 66-964). None of the tested variables influenced outcome.

CONCLUSIONS AND RELEVANCE

Radiation therapy seems to represent a viable treatment option in cats with intracranial tumours, relieving neurological signs and improving local tumour control. Radiation therapy may be considered for cats with tumours in complicated/inoperable localisations or for cases with a high peri- and postoperative risk.

Seizure etiologic classification and long-term outcome for cats with juvenile-onset seizures

OBJECTIVE To identify seizure etiologic classification for cats that developed seizures at < 12 months of age and describe the long-term outcome of affected cats. DESIGN Retrospective cohort study. ANIMALS 15 client-owned cats with seizures that began at < 12 months of age. PROCEDURES Information on each cat was obtained from the medical records, veterinarians, and owners. Inclusion required an onset of seizures before 12 months of age and a complete medical record, including a final diagnosis. RESULTS 7 of the 15 cats had structural epilepsy, 4 had idiopathic epilepsy, and 4 had reactive seizures. Median age at seizure onset was 27 weeks (range, 0.4 to 41 weeks). Cluster seizures were reported in 6 cats, and status epilepticus was reported in 2. Age at the onset of seizures, presence of cluster seizures, and seizure semiology (ie, generalized vs focal seizures) were not significantly associated with seizure etiologic classification. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that cats that developed seizures at < 12 months of age were more likely to have structural epilepsy than idiopathic epilepsy or reactive seizures. Therefore, advanced diagnostic imaging is recommended in cats with juvenile-onset seizures if metabolic and toxic causes are excluded.

Invasive nasal histiocytic sarcoma as a cause of temporal lobe epilepsy in a cat

Case summary

A 10-year-old neutered female domestic shorthair cat was presented with an acute onset of neurological signs suggestive of a right-sided forebrain lesion, temporal lobe epilepsy and generalised seizure activity. MRI of the head revealed an expansile soft tissue mass in the caudal nasal passages (both sides but predominantly right-sided) involving the ethmoid bone and extending through the cribriform plate into the cranial vault affecting predominantly the right frontal lobe and temporal lobe. Histopathological examination of the tumour revealed a histiocytic sarcoma.

Relevance and novel information

This is the first report of a cat with clinical signs of temporal lobe epilepsy due to an invasive, histiocytic sarcoma. Histiocytic sarcoma, although rare, should be included in the list of differential diagnoses for soft tissue masses extending through the cribriform plate. Other differential diagnoses are primary nasal neoplasia (eg, adenocarcinoma, squamous cell carcinoma, chondrosarcoma and other types of sarcomas), lymphoma and olfactory neuroblastoma. Temporal lobe epilepsy in cats can be the consequence of primary pathology of temporal lobe structures, or it can be a consequence of pathology with an effect on these structures (eg, mass effect or disruption of interconnecting neuronal pathways).

Consensus recommendations on standardized magnetic resonance imaging protocols for multicenter canine brain tumor clinical trials

The National Cancer Institute Comparative Brain Tumor Consortium, Patient Outcomes Working Group, propose a consensus document in support of standardized magnetic resonance imaging protocols for canine brain tumor clinical trials. The intent of this manuscript is to address the widely acknowledged need to ensure canine brain tumor imaging protocols are relevant and have sufficient equivalency to translate to human studies such that: (1) multi-institutional studies can be performed with minimal inter-institutional variation, and (2) imaging protocols are consistent with human consensus recommendations to permit reliable translation of imaging data to human clinical trials. Consensus recommendations include pre- and postcontrast three-dimensional T1-weighted images, T2-weighted turbo spin echo in all three planes, T2*-weighted gradient recalled echo, T2-weighted fluid attenuated inversion recovery, and diffusion weighted imaging/diffusion tensor imaging in transverse plane; field of view of ≤150 mm; slice thickness of ≤2 mm, matrix ≥ 256 for two-dimensional images, and 150 or 256 for three-dimensional images.

Surgical removal of a choroid plexus oncocytoma in an adult cat

An 11-year-old male castrated domestic shorthair cat presented with left central vestibular dysfunction. Magnetic resonance imaging of the brain revealed a large, extra-parenchymal, strongly contrast-enhancing mass at the level of the left cerebellopontine angle and compressing the cerebellum and brainstem. The mass was surgically excised via left rostral and sub-tentorial craniectomies and histopathology revealed an epithelial neoplasm composed of anastomosing cords of neoplastic cells that contained large amounts of finely granular hypereosinophilic cytoplasm and round nuclei. The cytoplasmic granules were variably positive with periodic acid-Schiff and modified Gomori trichrome. Immunohistochemical staining with anti-cytokeratin AE1/AE3 was diffusely positive. Electron microscopy revealed neoplastic cells that were full of electron-dense organelles consistent with mitochondria. This is the first case of a choroid plexus oncocytoma in the central nervous system of any domestic animal species and highlights the role of successful surgical intervention in extra-parenchymal neoplasia in the central nervous system.