Fig. 12
From: Manifestations of pilocytic astrocytoma: a pictorial review
A pilocytic astrocytoma involving optic pathways. a An axial T2-weighted image shows a large mass originating in the region of the optic chiasm/hypothalamus (arrows). Note the arachnoid cyst in the right middle cranial fossa (arrowheads). b An axial T2-weighted image in a higher level shows the hyperintense tumour extending to the optic radiations (arrows). On this T1-weighted image (c), the mass is isointense compared with grey matter. T1-weighted axial (d) and sagittal (e) post-contrast images show heterogeneous enhancement extending anteriorly towards the optic nerves and posteriorly towards the optic tracts. Note the enhancing nodule dorsal to the medulla due to dissemination of the pilocytic astrocytoma (arrows)