Optic Nerve Sheath Meningioma

Optic nerve sheath meningiomas (ONSMs) are rare tumors of the anterior visual pathway that usually arise from the meninges that surround the optic nerve, or-less commonly- from the surrounding tissue (like cavernous sinus, falciform ligament, sphenoid wing, or pituitary fossae), that extended into the orbit. They represent around 2% of orbital tumors, 2% of meningiomas and 33% of optic nerve neoplasms (optic nerve gliomas being the most common).