Limbic pattern lesions following medulloblastoma therapy in a child: Recurrence, infection, or autoimmunity?

Accurate differentiation between tumor recurrence and other neurological complications remains challenging in pediatric neuro-oncology. Medulloblastoma, the most common malignant pediatric brain tumor, may present with new intracranial lesions after surgery and chemoradiotherapy that mimic recurrence but actually arise from infection or autoimmune limbic encephalitis. We report a 5-year-5-month-old girl with cerebellar medulloblastoma (WHO CNS5 grade 4, non-WNT/non-SHH, Group 3/4) who developed fever, drowsiness, and vomiting 7 months post-therapy. Magnetic Resonance Imaging (MRI) revealed unilateral right anteromedial temporal and hippocampal fluid-attenuated inversion recovery hyperintensity with insular extension, restricted diffusion, and a small frontal microhemorrhage without contrast enhancement. Cerebrospinal fluid analysis confirmed herpes simplex virus-1 infection. Correlating MRI findings with cerebrospinal fluid results and tumor molecular profile allowed early antiviral treatment, distinguishing infection from recurrence or limbic encephalitis and avoiding unnecessary oncologic interventions. This case emphasizes the importance of multimodal imaging and laboratory correlation in the post-treatment evaluation of pediatric medulloblastoma.