Medulloblastoma is the most common malignant brain tumor in children, known for its high propensity to disseminate through the cerebrospinal fluid (CSF), particularly within the subarachnoid space. Leptomeningeal seeding, where tumor cells attach and proliferate within the leptomeninges, is a common manifestation. However, epidural seeding is an exceptionally rare occurrence, with very few cases documented in the literature. We present the case of an 8-year-old male diagnosed with anaplastic large cell medulloblastoma, who underwent complete tumor resection followed by radiotherapy and chemotherapy. Four years postoperatively, routine imaging revealed multiple thoracic spinal seedings and an epidural lesion at the S2-3 level. Surgical intervention confirmed the mass was confined to the epidural space, without intradural involvement, a notable finding given the rarity of this presentation. The mechanism behind epidural seeding remains unclear, though it was hypothesized that tumor cells may have been introduced during a lumbar puncture performed in the post-diagnosis period. This case contributes to the limited body of literature on epidural seeding in medulloblastoma, highlighting the importance of considering this rare phenomenon in long-term follow-up and surveillance of patients.

Modern approach for the treatment of posterior fossa medulloblastomas remains a challenge for pediatric neurosurgeons and pediatric oncologists and requires a multidisciplinary approach to optimize survival and clinical results. We report the surgical principles of the treatment of posterior fossa medulloblastomas in children and how to avoid technical mistakes especially in very young patients. We also report our experience in a series of 64 patients operated from a medulloblastoma between 2000 and 2018 in Lyon. All patients had a craniospinal MRI. Eighty-one percent of the patients (n=50) had strictly midline tumor while 19% (n=14) had lateralized one. Eleven percent (n=7) had metastasis at diagnosis on the initial MRI. Forty-one percent (n=29) had an emergency ETV to treat hydrocephaly and the intracranial hypertension. All patient underwent a direct approach and a complete removal was achieved in 78% (n=58) of the cases on the postoperative MRI realized within 48h postsurgery. Histological findings revealed classical medulloblastoma in 73% (n=46), desmoplastic medulloblastoma in 17% (n=11) and anaplastic/large cell medulloblastoma in 10% (n=7). Patients were classified as low risk in 7 cases, standard risk in 30 cases and high risk in 27 cases. Ninety-six percent (n=61) of the patient received radiotherapy. Seventy-six percent (n=48) received pre-irradiation or adjuvant chemotherapy. At last follow-up in December 2018, 65% (n=41) of the patient were in complete remission, 12% (n=8) were in relapse and 27% (n=15) had died from their disease. The overall survival at five , ten and fifteen years for all the series was of 76%, 73% and 65.7% respectively. Medulloblastomas remain a chimiosensible and radiosensible disease and the complete surgical removal represents a favorable prognostic factor. The extension of surgery has also to be weighted in consideration of the new biomolecular and genetic knowledge that have to be integrated by surgeons to improve quality of life of patients.

Despite the improvement in the overall management of medulloblastomas in recent years, certain phenomena and in particular postoperative cerebellar swelling remain an enigma. This rare complication, little described in the literature, is nonetheless life threatening for the patients. We report our experience about two children who developed severe cerebellar swelling with hydrocephalus and upward herniation soon after a gross total resection of a fourth ventricle medulloblastoma by a telo-velar approach. Despite rapid management of ventricular dilation and optimal medical intensive treatment of intracranial hypertension, both children died quickly after the surgery. Pathological examination analyses were in favour of anaplastic/large cell medulloblastoma. Diffuse cerebellar swelling with upward herniation may occur postoperatively in young children with anaplastic/large cell medulloblastoma with leptomeningeal spread. In the literature, only 4 cases have been so far described with delayed onset of symptoms. Two children survived with an aggressive management (decompressive surgery and early radio-chemotherapy). Cerebellar swelling is an unrecognised and sudden complication of posterior fossa surgery for metastatic anaplastic medulloblastoma with leptomeningeal dissemination in young children. An initial less invasive surgical approach could be considered in such cases, in order to prevent this complication with potentially tragic issue, and which cannot be managed with a CSF shunt alone.