Objective: Our objective was to prospectively examine the optic nerves in patients with clinically severe unilateral optic neuritis, using routine spin-echo and magnetization transfer MR imaging.
Subjects and methods: For 39 patients with such lesions, we calculated the magnetization transfer ratio along the involved intraorbital optic nerve and along the asymptomatic contralateral optic nerve in a mirror-image location. Magnetization transfer ratios were correlated with the imaging findings on routine spin-echo MR imaging.
Results: Magnetization transfer ratios were decreased in 33 of the 39 clinically symptomatic optic nerves, including 12 of the 18 clinically symptomatic optic nerves in which no abnormality was seen on routine spin-echo MR images obtained before and after administration of gadopentetate dimeglumine.
Conclusion: Magnetization transfer imaging reveals intraorbital optic nerve abnormalities in patients with optic neuritis even when such lesions are otherwise occult on routine magnetization transfer imaging.