Web-Vet Neurology Specialists
Brain Tumours
Primary brain tumours arise from the neurons, glia, and meninges. Secondary brain tumours represent those cancers that metastasize to the brain or from a distant primary site or affect nervous tissue, often by compression or invasion, by direct extension from adjacent tissue. Studies indicate that brain tumors are observed in 2-4.5% of dogs and 2% of cats that are subjected to necropsy examination. Brain tumours primarily affect middle-aged to older dogs and cats.
Radiation Therapy
This study provides preliminary evidence that radiotherapy outcomes are variable with intraventricular tumours, and some long-term survivors are noted.
Brain tumours can have a number of secondary pathological effects including uncompensated intracranial hypertension, paraneoplastic syndromes, drop metastases and tumour-associated brain dysfunction. Clinical signs associated with brain tumours depend mainly on the location of the tumour within the brain. Seizures and behavioural changes are very commonly reported clinical abnormalities with forebrain neoplasms and they are perceived to greatly affect the animal's quality of life. Irradiation of intracranial tumours has been shown to be effective at improvement of tumour-associated neurological dysfunction and prolongation of survival, especially when compared with palliative medical therapy. In this article, the authors aim to investigate the effect of radiotherapy on freedom from brain tumor-associated seizures and survival time in dogs. A longer period of seizure freedom and longer survival time was observed in dogs with brain tumours after radiotherapy compared to medical therapy.
The aim of this study was to determine whether long-term corticosteroid dependency can be minimized by use of succinct prednisone tapering following radiotherapy.
Nineteen dogs were treated using a “rapid-taper” protocol wherein corticosteroid dose reduction began 0 to 20 days after completing RT. Outcomes were compared with a retrospectively studied control group (“slow-taper”; N = 36 dogs) in which corticosteroids were tapered more slowly.
In the rapid-taper group, 84% were completely tapered off prednisone, vs 50% in the slow-taper group. Rates at which corticosteroids had to be reinstituted later were similar for the 2 groups (approximately 1 in 3 dogs). Adverse effect rates were similar for the 2 groups suggesting that lengthy courses of PO prednisone are avoidable after intracranial RT
Imaging
Grading of oligodendroglioma in dogs based on magnetic resonance imaging
Oligodendrolioma (OG) are classified as low grade (OG II) or high grade (OG III) based on the presence of at least 1 of 2 key histological features: microvascular proliferation and necrosis. In the absence of these 2 features, high number of mitotic figures, nuclear pleomorphism, anisokaryosis, anisocytosis, or cellular atypia are used to defined OG III. The presence of vascular proliferation and contrast enhancement (CE) on MRI has been suggested as prognostic in previous literature in humans. This study includes 32 dogs with histological diagnosis of intracranial OG among which there were 8 dogs with OG II and 24 dogs with OG III. Moderate to marked CE and ring patterns were present on MRI in dogs with OG III but not OG II. The presence of cystic structures, GRE signal voids, and necrosis was strongly associated with OG III.
The “Claw Sign” may aid in axial localization in cases of peripherally located canine glioma on MRI
This retrospective study aimed to report the sensitivity, specificity of the MRI claw sign in dogs with a histologically confirmed peripherally located glioma or meningioma.
A total of 27 cases, 11 glioma and 16 meningioma, were included. The postcontrast T1-weighted images were blindly evaluated. The sensitivity and specificity for the “claw sign” for the first session were 85.5% and 80%, respectively. The interobserver agreement for identifying the “claw sign” was moderate. These findings indicate the claw sign is supportive but not pathognomonic for intra-axial localization in cases of canine glioma on MRI.
The aim of this study was to directly compare histological brain sections to MRI sequence images and determine which sequence best correlates with tumor margins in dogs with glioma, histiocytic sarcoma, and meningioma.
Margins of signal intensity alterations (T2-weighted, FLAIR, T1-weighted and contrast enhancement) were compared directly to solid tumor and surgical margins identified on histology.
In glioma cases, margins drawn around T2-weighted hyperintensity were most similar to surgical margins. In both meningioma and histiocytic sarcoma margins of contrast enhancement were most similar to surgical margins.
This study focuses on the use of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the investigation and treatment planning of meningioma in cats and dogs. The authors suggest that presurgical ADC and FA measurement could predict a tumor's consistency and may provide useful information for considering operation techniques.
Canine Gliomas
The goal of this study was to improve existing glioma classification methods through creation of a histologic atlas of features. The long-term goal was to support future incorporation of clinical outcomes and genomic data into proposed simplified diagnostic schema.
193 cases of canine glioma were morphologically reclassified according to a new schema yielding a diagnosis of astrocytoma which were low-grade and high-grade, and oligodendroglioma which were also low-grade and high-grade. Sixteen cases (8.3%) could not be classified as oligodendroglioma or astrocytoma based on morphology alone and were designated as undefined gliomas.
The aim of this study was to evaluate possible associations between presenting complaint, tumour localisation, MRI features, survival times of dogs with suspected intracranial gliomas treated palliatively. Sixty dogs were included if a presumptive diagnosis of brain glioma was obtained based on an MRI scan and medical history.
French Bulldogs were overrepresented (40/60); 46 out of 60 dogs (77%) presented due to epileptic seizures (ES) and in 25/60 dogs (42%), cluster seizures or status epilepticus were the first manifestation of the disease.
Dogs with suspected gliomas located in the piriform lobe showed a higher probability of presenting due to epilepsy compared to dogs with glioma in other regions, and more frequently died or were euthanised because of increased ES. The median survival time was 61 days. Dogs with contrast-enhancing suspected gliomas had significantly shorter OS.
Clinical features, diagnosis, and survival analysis of dogs with glioma
The aim of this study was to characterize the clinicopathologic findings, diagnostic imaging features and survival of a large sample of dogs with glioma using the Comparative Brain Tumor Consortium diagnostic classification system.
91 dogs with histopathological diagnosis of glioma had their tumors reclassified according to the new canine glioma diagnostic scheme.
Although no associations were found between clinicopathologic information or survival and tumor type or grade, on MRI, oligodendrogliomas were associated with smooth margins and T1-weighted hypointensity compared to astrocytomas and undefined gliomas and were more commonly in contact with the ventricles than astrocytomas. Tumor spread to neighboring brain structures was associated with high-grade glioma
Cerebrospinal Fluid Drop Metastases of Canine Glioma: Magnetic Resonance Imaging Classification
Dissemination of glioma can occur as leptomeningeal nodules, diffuse leptomeningeal lesions, or ependymal lesions. This study describes these CSF drop metastases in 10 dogs with gliomas.
The CSF drop metastases appeared as leptomeningeal nodules in four dogs, diffuse leptomeningeal lesions in six dogs, and ependymal lesions in seven dogs; six dogs had a combination of lesion types.
Many metastases were T2-homogeneous and non-enhancing. Diffuse leptomeningeal lesions were seen as widespread extra-axial contrast-enhancement, very dissimilar to the primary mass. Primary masses were rostrotentorial, whereas metastases generally occurred in the direction of CSF flow, in ventricles, CSF cisterns, and the central canal or leptomeninges of the cervical or thoracolumbar spinal cord.
Chemotherapy for the treatment of intracranial glioma in dogs
This paper reviews the outcomes of 127 dogs with intracranial glioma, either presumed (n = 49) or histologically confirmed (n = 78), that received chemotherapy as leading or adjuvant treatment.
This review highlights the status of current chemotherapeutic approaches to intracranial gliomas in dogs, most notably oral temozolomide and oral lomustine - although evidence is weak, both drugs seem to have some positive effect on survival compared to palliative treatment.
Canine Meningioma &
Histiocytic Sarcoma
Magnetic Resonance Imaging and Histological Classification of Intracranial Meningiomas in 112 Dogs
The aims of this study were to (1) develop a histological classification scheme for grading canine meningiomas (based on the human WHO international classification scheme), (2) describe a subtype of meningioma not reported previously, (3) present an anatomical classification scheme based on tumor predilection sites, and (4) correlate MRI findings with subtype and grade of tumor.
112 dogs were studied -Meningiomas were overrepresented in the Golden Retriever and Boxer breeds with no sex predilection. The incidence of specific tumor grades was 56% benign (Grade I), 43% atypical (Grade II), and 1% malignant (Grade III). Grade I histological subtypes included meningothelial (43%), transitional (40%), microcystic (8%), psammomatous (6%), and angiomatous (3%). No statistically significant (P < .05) associations were found among tumor subtype or grade and any of the MRI features studied.
Histological Grading of Meningioma Part 1 Standardisation of canine meningioma grading: Inter-observer agreement and recommendations for reproducible histopathologic criteria
This study focused on standardising the human grading system applied to canine meningioma.
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.
Histological Grading of Meningioma Part 2 Standardization of canine meningioma grading: Validation of new guidelines for reproducible histopathologic criteria
The goal of this study was to validate the new guidelines for canine meningiomas and in conclusion found that the new grading guidelines for canine meningiomas are associated with an overall improvement in the inter-observer agreement and higher diagnostic accuracy in diagnosing grade 1 and grade 2 meningiomas.
This is a surgical treatment study looking at outcome of dogs undergoing resection for intracranial meningioma involving 4 referral centres in the UK. Among the key findings revealed by this study:
- There was no significant difference in survival time with the addition of any specific adjunctive therapy.
- Median long-term survival was 386 days.
- Dogs that had a transfrontal approach had a significantly reduced survival time compared to those that had a rostrotentorial approach.
- There was no association between meningioma subtype and survival time.
One of the main limitations of this study is the very heterogeneous population as well as variability in surgeon's experience. It certainly highlights and reminds us of the absence of clear consensus and lack of evidence-based treatment when it comes to adjunctive therapy following meningioma surgery.
This paper reviews clinicopathological characteristics of HS affecting the CNS in dogs. Although HS affecting the CNS is uncommon, the neurological form may be part of a disseminated multi-organ process (disseminated HS) or be confined to the CNS (primary HS).
In this study, marked CSF inflammation was characteristic of primary rather than disseminated HS. Neoplastic cells were detected in CSF of 52% of dogs. Also Corgis and Shetland Sheepdogs appear predisposed to primary CNS HS.
Histiocytic Sarcoma (HS) with Central Nervous System Involvement in Dogs: 19 Cases (2006–2012)
The objective of this study was to report the signalments, clinical signs, clinicopathologic and diagnostic imaging findings, treatment, and outcome of a series of dogs with HS and CNS involvement.
Retrievers and Pembroke Welsh Corgis were overrepresented in this cohort of dogs. Tumors involved the brain in 14 dogs and the spinal cord in 5. In 4 dogs, HS was part of a disseminated, multiorgan process whereas it appeared confined to the CNS in 15 dogs. Diagnostic imaging had variable appearances although extraaxial masses predominated in the brain. There was meningeal enhancement in all dogs that was often profound and remote from the primary mass lesion. Pleocytosis was present in all dogs with CSF evaluation. Median survival was 3 days.
Feline Meningioma
Pathological and immunohistochemical features of 45 cases of feline meningioma
The objective of this study was to investigate the histopathological subtypes and immunohistochemical features of feline meningioma - 45 cases were examined.
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 vimentin in 17 cases (43.6%) and E-cadherin in 36 cases (92.3%), demonstrating the utility of E-cadherin-immunohistochemistry for the diagnosis of feline meningiomas.
Intracranial Lymphoma
Clinical and magnetic resonance imaging features of lymphoma involving the nervous system in cats
This study of 31 cats aimed to describe the clinical and MRI features of lymphoma affecting the central (CNS) or peripheral (PNS) nervous system or both.
On MRI, lesions affecting the CNS were diagnosed in 18/31 cats, lesions in both CNS and PNS in 12/31, and lesions in the PNS only in 1/31. Intracranial lesions were diagnosed in 22 cats (extra‐axial, 7/22; intra‐axial, 2/22; mixed, 13/22). Infiltration of adjacent extra‐neural tissue was present in 11/31 cases. Contrast enhancement was seen in all lesions, being marked in 25/30. Meningeal enhancement was present in all but 2 cases. Four distinct MRI patterns were observed in cats with invasive intracranial lesions: nasopharyngeal mass invading the calvarium floor; mass centered on the cribriform plate involving nasal cavity and olfactory lobes; rostral brain and adjacent frontal sinus infiltration; and extra‐axial mass with tympanic bulla infiltration.
Feline lymphoma of the nervous system. Immunophenotype and anatomical patterns in 24 cases
This study aimed to describe the specific localization and anatomical pattern of 24 feline lymphomas of the nervous system for which the immunophenotype was identified by immunohistochemistry investigations to support the potential specific correlation between subtypes and anatomical patterns. In total 10 tumors affected the spinal cord, eight the brain, four the peripheral nerves, one involved both the brain and the spinal cord, and one simultaneously the brain and the optic nerves. 12 tumors consisted of B cell lymphomas, and six of T cell lymphomas, two cases were double-reactive lymphomas while two cases consisted of non-B non-T lymphomas. B cell lymphoma affected animals of 6.4 years of mean age, while the T cell lymphoma affected older animals (mean age of 11.1 years). CD44-expression confirmed a common malignant potential for all the anatomical patterns of the nervous system lymphoma in cats.
Pituitary Tumours
This paper described a dog with a large pituitary tumour treated by intratumoral injection via two manual CT-guided injections of radioactive holmium-166 microspheres. The authors report a 40% tumour volume reduction and improvement in the dog's quality of life, without any severe periprocedural side effects. This paper described in great detail the protocol used for this microbrachytherapy including the transsphenoidal approach to allow needle placement.
A multi-institutional retrospective study was performed, including dogs with PM treated with SRT (total dose 30 or 35 Gy in 5 daily fractions) or FRT (total dose 50–54 Gy in 19–20 daily fractions). The influence of potential prognostic/predictive factors was assessed, including pituitary: brain height, pituitary: brain volume, sex, age and endocrine status.
During the first 6 months after RT, 5/27 (19%) dogs treated with SRT and 3/17 (18%) dogs treated with FRT died or were euthanised because of progressive neurologic signs. The overall median survival time was 608 days. Young age at the time of treatment was significant for survival; the overall median survival time was 753 days for dogs <9 years of age and 445 days for dogs ≥9 years of age. Survival time was not associated with treatment type or any other factor.
Choroid Plexus Tumours, Ependymomas and Rarities
This retrospective evaluation of 12 cats and dogs with intraventricular tumors evaluated outcome and complications when treated with either radiation or radiation (RT) and ventriculoperitoneal shunting (VPS).
1 cat and 5 dogs treated with RT and 4 cats and 2 dogs treated with VPS/RT. Neurological worsening seen in 4/6 animals during single-modality RT and 2/6 died during RT. All dogs with VPS normalized clinically by the end of RT or earlier.
Imaging follow-up in 8 animals surviving RT showed a marked decrease in tumor volume. Median survival time was 162 days.
Overall the authors felt that ventriculoperitoneal shunting led to rapid normalization of neurological signs and RT had a measurable effect on tumor volume.
Magnetic resonance imaging features of intraventricular ependymomas in five cats
The purpose of this retrospective case series study was to describe the clinical and MRI characteristics of histopathologically confirmed intraventricular ependymomas.
In relation to normal gray matter, ependymomas appeared hyperintense on T2W, T2W-FLAIR, PD, and DW-EPI images; isointense on ADC images; and had subtle to strong contrast enhancement. Some variability was seen on T2*GRE and on T1W images with masses being isointense to hyperintense.
Four ependymomas were small and homogeneous, and one was centrally cavitated. All cats had obstructive hydrocephalus, transtentorial herniation, and foramen magnum herniation.