Global Hyperperfusion in the Brain at Onset of the Immune Reconstitution Inflammatory Syndrome in a Patient With Natalizumab-Associated PML

A 54-year-old woman with relapsing multiple sclerosis (EDSS 3.0) on treatment with natalizumab (14 infusions, an anti-JCV antibody index of 3.11) presented with blurred vision and ataxia.Progressive multifocal leukoencephalopathy (PML) was diagnosed following magnetic resonance imaging (MRI) (Figure 1) and positive CSF PCR for JCV (206 copies/mL).Four weeks later, she gradually became unconscious without clear PML deterioration, indicating immune reconstitution inflammatory syndrome (IRIS) development; however, MRI revealed no gadolinium enhancement (GE) (Figure 2).Thirty-four days after PML diagnosis, arterial spin labeling MRI revealed global hyperperfusion, with GE visible on day 55 (Figure 2).The coma persisted for 1 month; she gradually regained consciousness and eventually engaged in simple conversations.Serial brain MRI findings (Figure 2) were consistent with a previous Figure 1 FLAIR Images of Brain MRI Before (A) and After (B) PML Development New T2 lesions developed in the right frontal lobe and right pons.