Fig 4.

Within 1 month of the MR imaging shown in Fig 3, the patient was started on a course of natalizumab (Tysabri), 300 mg administered intravenously every 4 weeks. Repeat MR imaging after 6 months was performed. A, FLAIR-weighted sagittal FSE image of the brain shows improvement in the patchy high-signal-intensity area of the corpus callosum with resolution of lesions involving the brain stem structures and cerebellum. B, FLAIR-weighted axial FSE image shows marked improvement in the areas of demyelination involving the corpus callosum and bilateral periventricular white matter. C, Postcontrast T1-weighted axial FSE image shows only 1 small area of enhancement in the right periventricular white matter, with lack of enhancement of the rest of the enhancing lesions.