Optic Nerve Sheath Meningioma

In 1977 while talking about the difficulty in identifying small meningiomas involving the orbital apex, optic nerve sheath, and canal Susac, Smith, and Walsh wrote an article entitled The Impossible Meningioma.' The advent of CT scanning (allowing identification of enlarged optic nerve sheath and calcification) substantially improved the situation and the subsequent advent of MRI scanning with gadolinium and fat sat further advanced diagnostic armamentarium. In spite of these advances, optic nerve sheath meningiomas are often discovered after substantial delay. The fact that fractionated radiation therapy may substantially improve the prognosis underlies the importance of timely diagnosis and referral.'