MRI of chiasmatic optic pathway glioma

18-month-old child with chiasmatic glioma. T2-weighted MR images in the transverse axial plane (A1-C1) show a mass in the optic chiasm (asterisk) that extends anteriorly into the intracranial optic nerves (arrows) and posteriorly into the optic tracts (dashed arrows). T2-weighted MR images in the coronal plane (A2-C2) also demonstrate tumor extending anteriorly (A2) and posteriorly (C2) from the optic chiasm (B2). The level of each coronal image is indicated by the horizontal line on the axial image immediately above.