Acute optic neuritis in multiple sclerosis

(A) Gadolinium-enhanced, fat-suppressed, T₁-weighted magnetic resonance (MR) scan showing mild thickening and abnormal enhancement (arrow) throughout the left optic nerve in a 37-year-old woman with visual loss in her left eye. (B) Sagittal T₂-weighted FLAIR (fluid attenuated inversion recovery) MR scan, in which cerebrospinal fluid appears dark and areas of brain inflammation or demyelination appear high in signal, as shown in periventricular white matter (arrows).