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Medulloblastoma

Last Updated: March 27, 2020

Figure 1: The hyperdensity of this medulloblastoma on CT (top row left) is typical and representative of the tumor's hypercellularity. Likewise, the DWI (top row right) showed restricted diffusion also representing hypercellularity. This patient's lack of significant enhancement on this T1WI postcontrast image (bottom) is most typical of group 4 medulloblastomas. The intraventricular location is also typical, with these lesions sometimes visibly arising from the 4th ventricular roof.

Figure 2: Sagittal T1 post-contrast (top row left), axial T2-FS (top row right), DWI (middle row left), and ADC (middle row right) images demonstrate an enhancing mass in the 4th ventricle with restricted diffusion (bright on DWI and dark on ADC) compatible with hypercellular tumor. Multiple enhancing supratentorial and infratentorial nodules are noted along the surface of the cerebrum and cerebellum (top row left), compatible with CSF dissemination of tumor. Sagittal T1 post-contrast images of the cervical, thoracic, and lumbar (bottom row) spine demonstrate enhancing nodules along the dorsal surface of the spinal cord compatible with drop metastases in this patient with aggressive medulloblastoma.

Basic Description

  • Malignant, invasive primitive neuroectodermal tumor usually arising within the posterior fossa
  • Most common pediatric malignant posterior fossa tumor

Pathology

  • WHO grade IV
  • Divided into four molecular subtypes which originate in different locations:
    • Wingless (WNT): cerebellar peduncles, CPA cistern
    • Sonic hedgehog (SHH): cerebellar hemispheres
    • Group 3: 4th ventricle, midline
    • Group 4: 4th ventricle, midline
  • Divided into four distinct histologic subtypes: classic (most common), desmoplastic, large cell/anaplastic, and extensive nodularity

Clinical Features

  • Most commonly afflicts children ages 5-12; adult cases 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

Imaging Features

  • General
    • Appearance varies with location/subtype
    • Solid, rounded 4th ventricular mass most common
    • ± 4th ventricular effacement and distortion (in comparison with ependymoma, which often expands/enlarges the 4th ventricle)
    • Calcification and cysts occasionally present
    • Hemorrhage uncommon
    • CSF dissemination common, including drop metastases within the spinal canal (15-50%)
  • CT

    • Fairly homogeneous, mildly hyperdense 4th ventricular mass
    • ± hyperdense calcifications or hypodense cysts
    • Variable enhancement on contrast-enhanced CT (patchy or homogeneous)
  • MRI

    • T1WI: hypointense
    • T2WI: iso- 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
    • MR spectroscopy: elevated Cho, decreased NAA, ± lactate peak

Imaging Recommendations

  • MRI without and with IV contrast including both brain and spine due to risk of CSF dissemination

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Rachel Seltman, MD; Jacob A. Eitel, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.01.26

References

Brandes AA, et al. New perspectives in the treatment of adult medulloblastoma in the era of molecular oncology. Crit Rev Oncol Hematol. 2015;94:348-359.

Gerber NU, et al. Recent developments and current concepts in medulloblastoma. Cancer Treat Rev. 2014;40:356-365.

Koral K, et al. Imaging characteristics of atypical teratoid-rhabdoid tumor in children compared with medulloblastoma. AJR Am J Roentgenol. 2008;190:809-814.

Osborn AG, Salzman KL, Jhaveri MD. Diagnostic Imaging (3rd ed). Philadelphia, PA: Elsevier, 2016.

Yeom KW, et al. Distinctive MRI features of pediatric medulloblastoma subtypes. AJR Am J Roentgenol. 2013;200:895-903.

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