Posterior fossa giant tumefactive perivascular spaces: 8-year follow-up in an adolescent

Background: Cystic masses in the posterior fossa are ominous appearing lesions with broad differential diagnosis. Giant tumefactive perivascular spaces (GTPS) are rarely occurring pathological findings in the posterior fossa with unclear etiology and ill-defined long-term prognosis. Case Description: We present a case of a 15-year-old male diagnosed with posterior fossa GTPS. The patient remained asymptomatic during the 8-year follow-up after diagnosis with the serial magnetic resonance imaging (MRI) showing no change in the size and morphology of the lesion. Conclusion: This case supports prior literature on supratentorial GTPS suggesting that the natural history of GTPS is mostly benign. Identification of GTPS in the posterior fossa could prevent the patient from unnecessary surgery or other aggressive treatment modalities.