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American Journal of Neuroradiology 28:666-671, April 2007
© 2007 American Society of Neuroradiology

PEDIATRICS

Defining Optic Nerve Tortuosity

G.T. Armstronga,c, A.R. Localioc, T. Feyginb, L. Bilaniukb, P.C. Phillipsa, M.J. Fishera, B.L. Stromc and R. Zimmermanb

a Division of Oncology, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine Philadelphia, Pa
b Department of Radiology, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine Philadelphia, Pa
c Department of Biostatistics and Epidemiology, Center for Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, Pa

Address correspondence to Gregory T. Armstrong, MD, Department of Epidemiology and Cancer Control, St. Jude Children's Research Hospital, 332 N. Lauderdale St, Mail Stop 735, Memphis, TN 38105-2794; e-mail: greg.armstrong{at}stjude.org

BACKGROUND AND PURPOSE: Optic nerve tortuosity is one of several nonmalignant abnormalities documented on MR imaging in patients with neurofibromatosis type 1 and may be related to the development of optic pathway gliomas. This study seeks an operational definition for optic nerve tortuosity.

MATERIALS AND METHODS: A focus group of 3 pediatric neuroradiologists reviewed 20 MR images of the brain and orbits of patients suspected to have optic nerve tortuosity in the absence of optic pathway glioma and found 6 radiographic factors that occurred frequently. Subsequently, 28 MR images were assessed for the presence of optic nerve tortuosity, using a global assessment question that reflects a neuroradiologist's confidence in the presence of optic nerve tortuosity, and for the presence of the 6 radiographic factors, to identify a combination of these factors that best predicted a diagnosis of optic nerve tortuosity.

RESULTS: We found perfect inter-rater agreement between 3 readers on the presence/absence of tortuosity in 75% of cases. Lack of congruity of the optic nerves, in more than 1 coronal section and dilation of the subarachnoid space surrounding the optic nerves, when found together are sensitive (89%) and specific (93%) for a diagnosis of tortuosity on the global scale. The absence of these 2 factors, along with absence of deviation of the optic nerve within the axial plane, provides a reliable test to exclude tortuosity.

CONCLUSION: Lack of congruity of the optic nerves in more than 1 coronal section and dilation of the subarachnoid space surrounding the optic nerves together provide an operational radiographic definition of optic nerve tortuosity.






Copyright © 2008 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X