Optic nerve sheath meningiomas.

PURPOSE: To study the natural history and growth of optic nerve sheath meningiomas and evaluate their management outcome. DESIGN: Clinicopathologic retrospective noncomparative case series. METHODS: A retrospective study of 88 patients who were treated between 1976 and 1999 at the University of British Columbia and the University of Amsterdam. Clinical reports, imaging studies, and histopathologic findings were reviewed. RESULTS: The mean age at onset of symptoms was 40.3 years, and most were seen in middle-aged females. Patients typically presented with visual loss, frequently associated with optic atrophy or papilledema and occasionally optociliary shunt vessels. On imaging, the optic nerve demonstrated segmental or diffuse thickening of the sheath or globular growth. Calcification was seen in 31% of cases and was associated with slower tumor growth. Tumors with posterior components in the orbit had more frequent intracranial involvement. Intracranial extension was more frequent and had a greater growth rate in younger patients. Irregular margins in the orbit implied local invasion. A presenting visual acuity better than 20/50 correlated with longer preservation of vision. Patients who underwent radiotherapy showed improvement in their visual acuity, and tumor growth was halted. Optic sheath decompression did not preserve vision. En bloc tumor excision was associated with no detectable recurrence in contrast to debulked tumors that recurred. CONCLUSIONS: Meningiomas show characteristic indolent growth. Management therefore should be conservative in most cases. Radiotherapy is indicated in patients with progressive visual deterioration. Surgery, when indicated, should be an en bloc excision.

Magnetic resonance imaging of the orbit: Basic principles and anatomy.

This review article gives a basic introduction to the technical principles of magnetic resonance imaging for ophthalmologists and orbital surgeons and describes the anatomical structures that can be identified on high-resolution magnetic resonance images of the orbit. The meaning of general imaging parameters, specific weighting of the images, and the use of contrast agents, fat suppression techniques and surface coils is explained. Possible artifacts are also described. The advantages and disadvantages of MRI in comparison with computed tomography (CT) are discussed in order to give recommendations for the use of the appropriate imaging modality in patients with orbital disorders. Apart from delineating the course of the extraocular muscles, high-resolution MRI is able to depict not only all important blood vessels and cranial nerves of the orbit but also major septa of the orbital connective tissue system. Clinical applications are also mentioned to show that high-resolution MRI may contribute to a specific diagnosis in orbital disease.