Primary orbital meningiomas arise from the optic nerve sheath and may extend through the optic canal intracranially, or they may infiltrate the sphenoid wing producing hyperostosis. Nearly two thirds of orbital tumors, however, originate from outside the confines of the orbit

Rarely ectopic rests of arachnoid cells give rise to orbital meningiomas separate from the optic nerve sheath.

see Orbital Roof Meningioma