Irreversible disability and tissue loss in multiple sclerosis: a conventional and magnetization transfer magnetic resonance imaging study of the optic nerves.

OBJECTIVES To assess, by magnetic resonance imaging, the volumes and magnetization transfer ratio (MTR) values of optic nerves (ONs) from patients with multiple sclerosis (MS) who had incomplete or no visual recovery after optic neuritis; and to compare these quantities with those derived from ONs from patients with MS who showed a marked clinical recovery after optic neuritis, ONs from healthy volunteers, and ONs from patients with Leber hereditary optic neuropathy (LHON). METHODS Conventional and magnetization transfer magnetic resonance images of the ONs were obtained from 30 patients with MS, 18 healthy volunteers, and 10 patients with LHON. The ON from patients with MS were classified as clinically unaffected (n = 18); clinically affected with recovery (n = 20; visual acuity > or =20/25 at least 6 months after optic neuritis); and clinically affected with incomplete or no recovery (n = 22; visual acuity <20/25 at least 6 months after optic neuritis). The ON volumes and MTR values were measured. RESULTS Volumes (P =.002) and MTR values (P<.001) of the ONs from patients with MS and incomplete or no recovery were both lower than those of the ONs from patients with MS and recovery, but not different from those of the ONs from patients with LHON. Volumes and MTR values of the affected ONs from patients with MS and recovery did not differ from those of clinically unaffected ONs, which were similar to those of healthy volunteers. CONCLUSION These findings suggest that, in patients with MS, neurodegeneration is associated with persistent functional deficits secondary to incomplete recovery from relapses.