Frequency of Nonspecific Optic Nerve Sheath Enhancement on Magnetic Resonance Imaging

Optic nerve sheath enhancement (ONSE) on MRI is associated with a range of pathological conditions but may also occur in individuals without optic nerve disease. This study aimed to determine the prevalence, sensitivity, and specificity of ONSE among patients with and without known optic nerve pathology and to assess the impact of MRI field strength and demographic factors on ONSE interpretation.

This retrospective study included 115 patients with either known pathologic enhancement or no pathology who underwent MRI of the orbits between January 2010 and June 2023 at a single academic center. MRI scans were reviewed by a blinded neuroradiologist for presence or absence of ONSE. Patient demographics and MRI technical details, including field strength (1.5T or 3T), were recorded. Diagnostic performance metrics (sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV], accuracy) were calculated overall and stratified by MRI strength.

Among 115 patients (median age 63.2 years, 68% female, 90% White), ONSE was falsely identified in 7% of controls and missed in 13% of cases with known pathology. Overall, ONSE detection yielded a sensitivity of 87% and specificity of 93%. For 3T MRI, sensitivity was 100% and specificity was 90%; for 1.5T MRI, sensitivity was 75% and specificity 95%. PPV remained low across all groups, with highest NPV seen in 3T imaging (100%). No significant influence of age, sex, or race on ONSE detection was observed.

ONSE can be seen in a small proportion of patients without optic nerve pathology and may be missed in subtle disease, emphasizing the importance of clinical correlation. Higher field strength MRI may improve sensitivity for detecting pathologic ONSE but can have false positives. These findings underscore the need for cautious interpretation of ONSE, particularly in asymptomatic individuals or in the context of high-resolution imaging.