Ependymoma arising from the third ventricle mimicking optic neuritis in a dog

Abstract

Neurological examination of a 4.5-year-old female neutered labrador retriever was consistent with a lesion in the subcortical visual pathway (mainly affecting the left retina or optic nerve, and less likely the optic chiasm or right optic tract). Ophthalmic examination was unremarkable. MRI revealed enlargement of the left optic nerve and optic chiasm. A presumptive diagnosis of immune-mediated optic neuritis was made and immunosuppressive therapy was commenced. The dog re-presented 14 days later due to progressive deterioration and generalised seizure activity, and was euthanased. Postmortem examination revealed an anaplastic ependymoma extending from the rostral thalamus along the left optic nerve. Ependymoma can therefore mimic an optic neuropathy, such as immune-mediated optic neuritis, and should be considered as a differential diagnosis.