Medulloblastoma

  • Etiology: Small round blue cell tumor
  • Imaging:
    — Well defined and homogenous enhancing mass
    — Usually arising in midline in roof of fourth ventricle or inferior medullary velum
    — Can originate off midline such as from Foramen of Lushka
    — Hydrocephalus
  • Imaging CT without contrast: Well defined midline posterior fossa mass that is hyperdense due to increased cellularity of tumor
  • Imaging MRI:
    — Calcifications and cysts rare
    — T1WI: Isointense
    — T1WI post contrast: Homogenous enhancement in 90-95%
    — T1W2: Isointense
    — DWI: Often restricted diffusion due to high degree of cellularity and high nuclear to cytoplasmic ratio and scant interstitial fluid and decreased extra-cellular space
  • DDX: Ependymoma arises from floor of fourth ventricle while medulloblatoma arises from roof of fourth ventricle
  • Complications:
    — Systemic metastases in 15%
    — Drop metastases in 50% – indistinct folia and sulci on T1WI, leptomeningeal enhancement, sugar coating of cord
  • Treatment:
  • Clinical:
    — Peaks in childhood and early adult
    — Most common intracranial tumor in children

Radiology Cases of Medulloblastoma

MRI of medulloblastoma in the posterior fossa
Axial (above left), sagittal (above middle) and coronal (above right) T1 MRI with contrast of the brain shows a heterogeneously enhancing mass centered in the fourth ventricle which extends into the right cerebellar hemisphere. Axial T2 MRI (below left) shows the mass to be solid and on diffusion weighted imaging (below right) the mass demonstrates diffusion restriction.
MRI of medulloblastoma
Sagittal T1 MRI without (left) and with (right) contrast of the brain shows a hypointense signal mass filling and distending the fourth ventricle that enhances homogeneously.

Radiology Case of Medulloblastoma With Drop Metastases To The Spinal Cord

MRI of spinal drop metastases in medulloblastoma
Sagittal (left and middle) T1 MRI with contrast of the spine shows diffuse enhancement along the cerebellar folia and the anterior and posterior aspects of the entire spinal cord. Axial T1 MRI with contrast of the spine (right) shows the enhancement to be somewhat nodular in nature around the spinal cord.