Case: A 20 month-old male presents to the ED with complaints of increasingly unsteady gait and vomiting, who on exam, is found to have bilateral papilledema. The following MRI is obtained. What do you see?


Sagittal T-1 Image


MRI Brain: T1- weighted Image


MRI Brain: Coronal FLAIR

Case courtesy of Dr Abdallah Khateeb , From the case rID: 45608

Diagnosis: Pilocytic Astrocytoma (formerly juvenile Pilocytic Astrocytoma)

Official Radiology Read (per Dr. Khateeb)

Impression: 1.) Large cystic mass at the right posterior fossa with peripheral thick nodular enhancement. 2.) Significant mass effect on the cerebellum and the fourth ventricle, crowded foramen magnum, signs of obstructive hydrocephalus and transependymal edema.


Pilocytic Astrocytoma is a WHO grade 1 tumor, and generally confers a favorable prognosis. In fact, these tumors are considered curable if the entire tumor is resected . As such, the primary goal of therapy is resection. Recurrence is rare, as is malignant spread. Tumors are most commonly found in the cerebellum, but are also found in the brainstem, supratentorial structures, and the hypothalamus (Burkhard  et al, 2003).  Prognosis is excellent, but relies on gross-total resection.

Imaging Findings (Lee et al, 1989)

  • A majority of tumors are oval or round  (as seen in our case)
  • A majority of tumors are cystic
  • On MRI, lesions are hypo- to isointense on T1 weight images and hyperintense on T2 series.

Faculty Reviewer: Brad DeNardo, MD


Burkhard C et al. “A population based study of the incidence and survival in patients with pilocytic astrocytoma.” J Neurosurg. 2003; 98: 1170-1174

Lee Y et al. “Juvenile Pilocytic Astrocytomas: CT and MR Characteristics.” AJNR. 1989; 10: 363-370