Medulloblastoma (MB), a highly malignant neuroepithelial brain tumor, is the most common malignant brain tumor in children, but only accounts for <1% in adults. Standard treatment for adults has not been established, often adapting from pediatric guidelines. Vismodegib, a targeted therapy for the sonic hedgehog (SHH) subgroup of adult MBs, has demonstrated potential for recurrent MB but its long term efficacy and safety warrant further research.

Case: This is a case of a 26-year-old female who presented with occipital headaches. Imaging revealed a heterogeneously enhancing right cerebellar mass with areas of cystic degeneration and necrosis. She underwent resection, with pathology consistent with medulloblastoma, WHO Grade 4, dysplastic/nodular, SHH-activated, P53 wild type. Post-operatively, she had craniospinal irradiation (CSI) with protons, followed by adjuvant chemotherapy using the Packer regimen (cisplatin, lomustine, and vincristine). She only tolerated 2 cycles due to significant hematotoxicity. She subsequently developed leptomeningeal spread along the left vestibulocochlear nerve, cervical and lumbar spine. Vismodegib, a highly selective SHH inhibitor, was started and the patient was stable on this regimen for 3 years. Vismodegib was stopped following a spontaneous right thalamic hemorrhage. No bleeding risk factors and aneurysms were identified.