A fifteen y/o woman was brought to medical attention because of rapidly progressive gait disturbance and incoordination. The neurologic examination revealed deep tendon hyperreflexia, a right Babinski's sign, severe ataxic gait and frank cerebellar signs wich predominated at the left side. CSF analisys showed intrathecal IgG synthesis with oligoclonal bands. Proton density-weighted MRI images discloses predominantly periventricular white matter hyperintensities with radial distribution and similar changes in the cerebellar hemispheres and brachium pontis. T1-weighted images show hypointensities in the same locations. . The ocurrence of a relapse some months later confirmed the diagnosis. Try to make the diagnosis Having problems to partipate?