• Well circumscribed mass within the right ventricle that is hypointense on T1-weighted images, heterogeneously hyperintense on T2-weighted images and displays contrast enhancement
• Within the mass are multiple foci of T2* susceptibility
• The mass results in subfalcine herniation, caudal transtentorial herniation, compression of the fourth ventricle, and dilation of the right lateral ventricle

1. Space occupying mass of the right ventricle resulting in obstructive hydrocephalus. Differentials include choroid plexus papilloma, ependymoma, oligodendroglioma, or cholesterol granuloma
2. Differentials for the T2* signal voids within the mass include hemorrhage or mineral
3. Mild edema of the midbrain

• Due to the MRI findings and a poor prognosis, the patient was euthanized and a necropsy was performed
• Histologic diagnosis: ependymoma

Ependymomas

• Rare tumors that arise from the ependymal cells that line the cerebral ventricles and central canal of the spinal cord
• 4 case reports in horses (Lindsey, 2015)
• MRI characteristics:
  • Well demarcated iso-to hypointenseon T1-weighted images
  • Hyperintenson T2-weighted images
  • Variable contrast enhancement on post contrast images
  • Susceptibility artifact due to foci of calcification or hemorrhage

1. Lindsey C, AschenbroichS, et al. Pathology in practice. Ependymoma of the right ventricle with internal hydrocephalus in a horse. JAVMA 2015; 246 (10):1067-1069.