Computed tomography of lesions of the optic nerve.

ABSTRACT

Computed tomographic (CT) findings in 25 patients with various optic nerve lesions were reported. Neoplasms of the optic nerve/sheath particularly optic nerve gliomas and sheath meningiomas were found to be the major causes of the enlargement of the optic nerve in this series. Optic nerve gliomas is the most common lesion in children while the sheath meningioma usually occurs in adult. CT appearance of these tumours can appear as uniform thickening or uniform enlargement of the entire nerve. However, differentiation between the two tumours can be made by contrast enhancement. Enhancement of optic nerve sheath meningioma on CT is usually more marked than optic canal is also pathognomonic railroad track appearance is often identified. Typical hyperostosis around the optic canal is also pathognomonic for meningioma. Other tumours especially lymphomas, leukaemia and carcinomas of paranasal sinuses and nasopharynx can produce enlargement of the optic nerve/sheath by infiltration or direct compression to the nerve. In addition, nonneoplastic processes such as optic nerve/sheath on CT. Certain clinical and computed tomographic features permit distinction of these non-neoplastic conditions from tumours.