What is the accuracy of MRI for optic neuritis imaging?

Updated: Apr 02, 2019
  • Author: Pil (Peter) S Kang, MD; Chief Editor: James G Smirniotopoulos, MD  more...
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Although not specifically relevant to optic neuritis, false-positive results in orbital imaging can result from failure of complete fat saturation related to magnetic susceptibility artifact from dental amalgam and air–soft tissue interfaces, particularly at the inferior margin of the orbit. This is true especially for frequency-selective fat-saturation techniques but less so for inversion recovery sequences.

Fat-saturation failure can mimic orbital edema on multiecho-train, T2-weighted images or enhancement on fat-suppressed, T1-weighted images. Careful evaluation of the tissue surrounding the orbit should reveal the true cause of signal distortion. This artifact should not occur in optic neuritis, because the lesion of optic neuritis is confined to the nerve, but it can potentially mislead the interpreter to conclude that more diffuse orbital inflammation is the cause of vision loss.

Occasionally, the enhancement pattern in optic neuritis is a peripheral tram-track pattern. Potentially, this can be confused with the enhancement pattern of optic nerve meningioma. However, the optic neuritis pattern should be distinguished from the meningioma pattern by enhancement limited to the nerve, rather than the sheathlike pattern of meningioma; by the absence of significant mass or expansion; and by the clinical features of acute onset vision loss and pain.

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