Presentation
Occipital headache, nausea, and vomiting for three weeks.
Patient Data
In the posterior fossa, an intra-axial lesion of rounded morphology is identified within the right cerebellar hemisphere, with defined edges and heterogeneous, thin septa in its anterior portion. It is cystic, predominantly hypointense in T1 and hyperintense in T2 with suppression in FLAIR, without restriction to diffusion or artifact on susceptibility-weighted imaging. It has mass effect displacing the vermis and left cerebellar hemiphere towards the left with partial compression of the fourth ventricle but without hydrocephalus.
In addition, it has bone remodeling in the right occipital region.
Case Discussion
On MRI, pilocytic astrocytomas are typically cystic (hypointense or isointense on T1 sequences and hyperintense on T2 weighted images with suppression on FLAIR images) and have an enhancing mural nodule.
They occur more frequently in the posterior fossa at the level of the cerebellum in young patients. In adult patients, or patients with NF1 they occur more frequently in the supratentorial compartment.
In this patient, there is a cystic mass that shows findings suggestive of a pilocytic astrocytoma. This was confirmed with histopathology following surgical resection.
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