- pilocytic astrocytoma occurring in childhood
- involves optic nerves, chiasm and optic tracts
- chiasmal lesions often extend to hypothalamus and is of a higher histological grade
- associated with NF-1 (chiasmatic uncommon)
- indolent clinical course
MRI
- iso to hypointense of T1
- hyperintense on T2
- variable Gd+ enhancement
- diffuse fusiform expansion of nerve can occur from subarachnoid dissemination