Astrocytomas and oligodendrogliomas represent one third of histologically confirmed canine brain tumors. Our purpose was to describe the magnetic resonance (MR) imaging features of histologically confirmed canine intracranial astrocytomas and oligodendrogliomas and to examine for MR features that differentiate these tumor types.Thirty animals with confirmed astrocytoma (14) or oligodendroglioma (16) were studied.All oligodendrogliomas and 12 astrocytomas were located in the cerebrum or thalamus, with the remainder of astrocytomas in the cerebellum or caudal brainstem. Most (27/30) tumors were associated with both grey and white matter. The signal characteristics of both tumor types were hypointense on T1-W (12 each) and hyperintense on T2-W

Background: The reliability and validity of magnetic resonance imaging (MRI) for detecting neoplastic, inflammatory, and cerebrovascular brain lesions in dogs are unknown.Objectives: To estimate sensitivity, specificity, and inter-rater agreement of MRI for classifying histologically confirmed neoplastic, inflammatory, and cerebrovascular brain disease in dogs.Animals: One hundred and twenty-one client-owned dogs diagnosed with brain disease (n = 77) or idiopathic epilepsy (n = 44).Methods: Retrospective, multi-institutional case series; 3 investigators analyzed MR images for the presence of a brain lesion with and without knowledge of case clinical data. Investigators recorded most likely etiologic category (neoplastic, inflammatory, cerebrovascular) and most likely specific disease for all brain lesions. Sensitivity, specificity, and inter-rater agreement were calculated to estimate diagnostic performance.Results: MRI was 94.4% sensitive (95% confidence interval [CI] = 88.7, 97.4) and 95.5% specific (95% CI = 89.9, 98.1) for detecting a brain lesion with similarly high performance for classifying neoplastic and inflammatory disease, but was only 38.9% sensitive for classifying cerebrovascular disease (95% CI = 16.1, 67.0). In general, high specificity but not sensitivity was retained for MR diagnosis of specific brain diseases. Inter-rater agreement was very good for overall detection of structural brain lesions (j = 0.895, 95% CI = 0.792, 0.998, P < .001) and neoplastic lesions, but was only fair for cerebrovascular lesions (j = 0.299, 95% CI = 0, 0.761, P = .21).Conclusions and Clinical Importance: MRI is sensitive and specific for identifying brain lesions and classifying disease as inflammatory or neoplastic in dogs. Cerebrovascular disease in general and specific inflammatory, neoplastic, and cerebrovascular brain diseases were frequently misclassified.

Background: Magnetic resonance imaging (MRI) is a correlate to physical examination in various myelopathies and a predictor of functional outcome.Objectives: To describe associations among MRI features, neurological dysfunction before MRI, and functional outcome in dogs with disk herniation.Animals: One hundred and fifty-nine dogs with acute thoracolumbar disk herniation. Methods: Retrospective case series. Signalment, initial neurological function as assessed by a modified Frankel score (MFS), and ambulatory outcome at hospital discharge and 43 months (long-term) follow-up were recorded from medical records and telephone interview of owners. Associations were estimated between these parameters and MRI signal and morphometric data.Results: Dogs with intramedullary T2W hyperintensity had more severe pre-MRI MFS (median 2, range 0-4) and lower ambulatory proportion at long-term follow-up (0.76) than those dogs lacking hyperintensity (median MFS 3, range 0-5; ambulatory proportion, 0.93) (P5.001 and .013, respectively). Each unit of T2W length ratio was associated with a 1.9 times lower odds of long-term ambulation when adjusted for pre-MRI MFS (95% confidence interval 1.0-3.52, P5.05). Dogs with a compressive length ratio 41.31 (which was the median ratio within this population) had more severe pre-MRI MFS (median 3, range 0-5) compared with those with ratios 1.31 (median MFS 3, range 0-4; P5.006).Conclusions and Clinical Importance: MRI features were associated with initial injury severity in dogs with thoracolumbar disk herniation. Based on results of this study, the T2W length ratio and presence of T2W intramedullary hyperintensity appear to be predictive of long-term ambulatory status.

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Magnetic resonance (MR) imaging characteristics are commonly used to help predict intracranial disease categories in dogs, however, few large studies have objectively evaluated these characteristics. The purpose of this retrospective study was to evaluate MR characteristics that have been used to differentiate neoplastic, inflammatory, and vascular intracranial diseases in a large, multi‐institutional population of dogs. Medical records from three veterinary teaching hospitals were searched over a 6‐year period for dogs that had diagnostic quality brain MR scans and histologically confirmed intracranial disease. Three examiners who were unaware of histologic diagnosis independently evaluated 19 MR lesion characteristics totaling 57 possible responses. A total of 75 dogs with histologically confirmed intracranial disease were included in analyses: 51 with neoplasia, 18 with inflammatory disease, and six with cerebrovascular disease. Only strong contrast enhancement was more common in neoplasia than other disease categories. A multivariable statistical model suggested that extra‐axial origin, T2‐FLAIR mixed intensity, and defined lesion margins were also predictive of neoplasia. Meningeal enhancement, irregular lesion shape, and multifocal location distinguished inflammatory diseases from the other disease categories. No MR characteristics distinguished vascular lesions and these appeared most similar to neoplasia. These results differed from a previous report describing seven MR characteristics that were predictive of neoplasia in dogs and cats. Findings from the current study indicated that the high performance of MR for diagnosing canine intracranial diseases might be due to evaluator recognition of combinations of MR characteristics vs. relying on any one MR characteristic alone.