Arachnoid hyperplasia in optic nerve glioma: confusion with orbital meningioma.

A case is reported of an optic nerve glioma with a marked degree of arachnoid hyperplasia which was initially diagnosed as an optic nerve meningioma. Hyperplasia of the arachnoid was also the underlying cause for expansion of the optic canal. The relationship between arachnoid hyperplasia in optic nerve glioma and meningioma of the optic nerve sheath in childhood is discussed.