MRI findings in six dogs with ependymoma of the brain and spinal cord.

There are few published descriptions of the MRI appearance of canine intracranial or spinal cord ependymoma. In this multicenter, retrospective, secondary analysis, case series study, three veterinary radiologists independently reviewed and recorded imaging characteristics of MRI studies in six dogs with histopathologically confirmed ependymoma (three intracranial and three spinal cord cases). A consensus was reached when there was disagreement on specific features. All intracranial ependymomas had forebrain location, heterogeneous signal intensity in T1-weighted (T1W) and T2-weighted (T2W) images, heterogeneous contrast enhancement, and hyperintensity in T2W images. Two ependymomas had an intraventricular location; one was intra-axial. Other imaging features included intralesional cyst-like structures, intralesional hemorrhage, and perilesional edema. Dogs with spinal cord ependymoma had intramedullary lesions located in the cervical or thoracic spinal cord. Spinal cord ependymomas were isointense and homogeneous in T1W images and hyperintense in T2W images. Lesion location relative to the central canal of the spinal cord was variable. All three spinal cord ependymomas had perilesional T2W hyperintensity and moderate, heterogeneous contrast enhancement. None of the spinal cord ependymomas had intralesional cyst-like structures. One spinal cord ependymoma had evidence of drop metastases (diffuse, leptomeningeal). MRI features of canine ependymomas overlap with those of other diseases of the brain and spinal cord. Ependymoma should be considered a differential diagnosis for dogs with intraventricular, intra-axial forebrain, or intramedullary spinal cord masses.