Pediatric posterior fossa ganglioglioma: unique MRI features and correlation with BRAF V600E mutation status.

Ganglioglioma (GG) is a rare pediatric brain tumor (1-4 %) with neoplastic glial and neuronal cells. Posterior fossa GGs (PF GGs) occur less frequently than supratentorial GGs (ST GGs). The BRAF V600E mutation has been reported in GGs and carries therapeutic implications. We compare the presenting symptoms, magnetic resonance imaging, BRAF V600E mutation status, treatment, and prognosis in children with ST and PF GGs. The neuro-oncology database at a tertiary care Children's Hospital was retrospectively reviewed from 1995 to 2010 for patients with ST and PF GG. All available imaging was reviewed. Symptoms, BRAF V600E mutation status, treatment, and survival data were collected from the electronic medical record and analyzed. Our series consisted of 11 PF GG and 20 ST GG. Children with PF GG presented with ataxia, cranial nerve deficits and long tract signs whereas the majority with ST GGs presented with seizures. On imaging, PF GGs were infiltrative and expansile solid masses with dorsal predominant "paintbrush" enhancement whereas ST GGs were well circumscribed mixed solid and cystic masses with heterogeneous enhancement. Five of 11 (45%) PF GGs and 6 of 9 (67%) ST GGs expressed the BRAF V600E mutation. No unique imaging features were identified in BRAF V600E mutation positive tumors. The majority of ST GGs were treated with surgery alone, whereas the majority of PF GGs required multimodality therapy. PF GGs had worse progression-free survival and a higher mortality rate compared with ST GGs. Unlike ST GGs, PF GGs are expansile, infiltrative, show dorsal predominant "paintbrush" enhancement, are not amenable to gross total resection, and have worse progression-free survival and mortality.