Background: Detecting early progressive multifocal leukoencephalopathy-immune reconstitution inflammatory syndrome (PML-IRIS) is clinically relevant.
Objective: Evaluating magnetic resonance imaging (MRI) changes following natalizumab (NTZ) discontinuation and preceding PML-IRIS.
Methods: MRIs (including diffusion-weighted imaging (DWI), T2-weighted fluid-attenuated inversion recovery (T2-FLAIR), post-contrast T1-weighted sequences) were performed every week following PML diagnosis in 11 consecutive NTZ-PML patients. PML expansion, punctate lesions, contrast-enhancement, and mass-effect/edema were evaluated on each MRI sequence, following NTZ discontinuation.
Results: PML-IRIS occurred from 26 to 89 days after NTZ discontinuation. MRI changes prior to early PML-IRIS appeared significantly more pronounced using DWI compared to T2-FLAIR imaging (p < 0.003). Two DWI features (marked PML expansion, punctate lesions) systematically preceded contrast-enhancement.
Conclusion: Subtle changes may occur on DWI preceding contrast-enhancement.
Keywords: Multiple sclerosis; diffusion-weighted imaging; immune reconstitution inflammatory syndrome; magnetic resonance imaging; natalizumab.