- Malignant, invasive primitive neuroectodermal tumor usually arising within the posterior fossa
- Most common pediatric malignant posterior fossa tumor
- WHO grade IV
- Divided into 4 molecular subtypes that originate in different locations:
- Wingless (WNT): cerebellar peduncles, cerebellopontine angle (CPA) cistern
- Sonic hedgehog (SHH): cerebellar hemispheres
- Group 3: fourth ventricle, midline
- Group 4: fourth ventricle, midline
- Divided into 4 distinct histologic subtypes: classic (most common), desmoplastic, large cell/anaplastic, and extensive nodularity
- Most commonly afflicts children aged 5 to 12 years; adult cases are rare
- Common presenting signs/symptoms are related to increased intracranial pressure/hydrocephalus
- Headache, nausea, vomiting, altered mental status, papilledema, macrocephaly
- Treatment: surgical resection ± adjuvant chemoradiation
- Prognosis varies with molecular subtype and histology:
- Wingless most favorable
- Group 3 least favorable
- Appearance varies with location/subtype
- Solid, rounded fourth ventricular mass most common
- ±Fourth ventricular effacement and distortion (in comparison with ependymoma, which often expands/enlarges the fourth ventricle)
- Calcification and cysts occasionally present
- Hemorrhage uncommon
- Cerebrospinal fluid (CSF) dissemination common, including drop metastases within the spinal canal (15%–50%)
- Fairly homogeneous, mildly hyperdense fourth ventricular mass
- ±Hyperdense calcifications or hypodense cysts
- Variable enhancement on contrast-enhanced CT imaging (patchy or homogeneous)
- T1WI: hypointense
- T2WI: isointense to hyperintense
- FLAIR: improved delineation of tumor and CSF; minimal peritumoral edema
- T1WI+C: majority show heterogeneous enhancement, although variable patterns exist; may see CSF dissemination throughout neuraxis
- DWI: demonstrates DWI-bright, ADC-dark diffusion restriction
- MRS: elevated Cho, decreased NAA, ± lactate peak
- MRI without and with intravenous contrast including both brain and spine due to risk of CSF dissemination
For more information, please see the corresponding chapter in Radiopaedia.
Contributors: Rachel Seltman, MD, and Jacob A. Eitel, MD
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Gerber NU, Mynarek M, von Hoff K, et al. Recent developments and current concepts in medulloblastoma. Cancer Treat Rev 2014;40:356–365. doi.org/10.1016/j.ctrv.2013.11.010.
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