Clinical, magnetic resonance imaging, histopathological features, treatment options and outcome of spinal ependymoma in dogs: 8 cases (2011-2022).

Objectives: This study aims to report on the clinical magnetic resonance imaging, histological features, treatment options and outcomes of spinal ependymomas in dogs.

Materials and methods: Retrospective evaluation of medical records from dogs histologically confirmed spinal ependymomas with clinical presentations, magnetic resonance imaging findings, histological aspects, treatment options and outcomes.

Results: Eight dogs presented with acute to subacute onset of para- or tetraparesis. Magnetic resonance imaging findings included intramedullary oval-shaped space-occupying lesions that appeared hyperintense on T2-weighted images isointense on T1-weighted images and exhibited marked homogeneous or ring contrast enhancement. A peculiar feature, previously described only in human ependymomas, was observed in three patients - a T2-weighted hypointense rim, termed hemosiderin cap sign. Haematomyelia with necrotic foci was observed in one dog. Surgery, when performed, enabling a definitive intra-vitam diagnosis. Histological examination revealed that rosettes and pseudo-rosettes as disposition of neoplastic cells were the most common features reported. Furthermore, cerebrospinal fluid metastases were identified in one case.

Clinical significance: Clinical and histopathological findings in our case series were consistent with those previously reported in the literature. Magnetic resonance imaging features were fairly typical and highly suggestive of spinal ependymomas. The hemosiderin cap sign may aid in the presumptive intra-vitam diagnosis of these rare spinal tumours. Additionally, we described cerebrospinal fluid spread of neoplastic cells and subsequent multifocal or metastasis presentations. Surgery offered a dual benefit by facilitating intra-vitam diagnosis and, in some cases, extending survival time.