Unusually slow progression of a high-grade intramedullary oligodendroglioma in a dog: serial magnetic resonance imaging findings and clinical course over two years.

A 7.5-year-old spayed female French Bulldog presented for back pain that did not respond to conservative management after the dog had jumped off a couch. Magnetic resonance imaging (MRI) identified an intramedullary mass that was T2 hyperintense, T1 iso- to hypointense, short tau inversion recovery (STIR) hyperintense, strongly rim-enhancing, and centrally suppressed on post-contrast T2-fluid-attenuated inversion recovery (FLAIR) images. Despite a suspected glial cell neoplasm, clinical signs initially improved with palliative treatment. Follow-up MRI 2 years later showed progressive enlargement of the lesion, with newly noted multiseptated regions. Histopathology indicated a high-grade oligodendroglioma.