Natalizumab (tysabri)-associated progressive multifocal leukoencephalopathy: insights from perfusion magnetic resonance imaging.

A case of natalizumab-associated progressive multifocal leukoencephalopathy in a 38-year-old woman is presented showing characteristics on magnetic resonance imaging (MRI) with high signal on T2-weighted images and patchy contrast enhancement. After 5 days of plasma exchange therapy, contrast enhancement decreased, but the abnormality on T2-weighted images increased. Perfusion MRI at this time demonstrated significantly increased blood flow to the lesion. Thirteen days after initiation of treatment, perfusion MR returned to normal in advance of significant anatomical changes on conventional MRIs. This case suggests that MR perfusion imaging may be helpful in monitoring the treatment of patients with natalizumab-associated progressive multifocal leukoencephalopathy.