Multiple sclerosis relapse management — high-dose IV methylprednisolone vs oral steroids, when to use?

28F with known RRMS on natalizumab, presents with a new relapse: left lower limb weakness (grade 4/5), unsteady gait, and left-sided numbness over 5 days. Brain MRI shows new T2/FLAIR lesion in right internal capsule with gadolinium enhancement. She cannot walk independently. JC virus antibody index is 2.8. EBV and VZV serology negative. Per ECTRIMS/EAN 2023 guidelines, should she receive IV methylprednisolone 1g/day x 3-5 days, or is oral prednisolone 500mg/day equivalent? What is the preferred choice for functional recovery? Should plasma exchange be considered if she fails steroids?