Recurrent Ependymoma of the Cerebellopontine Angle and Radiation-Induced Pleomorphic Xanthoastrocytoma: A Case Report

Introduction: The majority of posterior fossa ependymomas arise within the ventricular system. Extra-axial, extraventricular ependymomas are rarely encountered in posterior fossa. We report a complex case of a posterior fossa ependymoma with spinal drop metastasis, as well as the first report of radiation-induced pleomorphic xanthoastrocytoma and extra-axial ependymoma of the posterior fossa.

Methods: Case report.

Case Report: A 9-year-old girl presented with progressive nausea, vomiting, and headaches over a period of 3 months. Magnetic resonance imaging (MRI) demonstrated an intra-axial right cerebellar lesion. She underwent excision of an anaplastic ependymoma (WHO grade III) followed by external beam radiotherapy. Following a quiescent period of 16 years, MRI demonstrated a cystic lesion arising from the previous resection site as well as a homogenously enhancing intrathecal tumor at the level of S2. Histopathological analysis from a repeat resection was consistent with a pleomorphic xanthoastrocytoma (WHO grade II). Routine follow-up showed slight enhancement within the right cerebellopontine resection bed suggestive of recurrence for which she underwent resection followed by proton beam therapy for pleomorphic xanthoastrocytoma. The Lumbosacral mass was managed conservatively. Two years later, she presented to our institution with a heterogeneously enhancing extra-axial lesion located in the right cerebellopontine angle along the medulla. She underwent a gross-total resection of a low grade ependymoma (WHO grade II) without complications or new deficits.

Conclusion: Extra-axial ependymomas are uncommon in the posterior fossa. Gross-total resection is the treatment of choice. Radiation-induced malignancies should be considered in instances of delayed recurrence with slightly different histology. Long-term follow-up is essential for early detection of local recurrence and spinal drop metastasis.