title: Magnetic resonance imaging pattern in natalizumab-associated progressive multifocal leukoencephalopathy.
abstract: OBJECTIVE
  Natalizumab is an effective treatment for patients with multiple sclerosis (MS) that is associated with a risk of progressive multifocal leukoencephalopathy (PML). Recommendations were published in 2006 to improve early diagnosis of PML using magnetic resonance imaging (MRI). However, due to the small number of MS patients initially diagnosed with PML, the imaging criteria could only be derived from PML lesions in patients with human immunodeficiency virus. Therefore, there is an urgent need to assess the MRI characteristics of PML in MS patients to update the existing recommendations.
  
  
  METHODS
  In this retrospective review, the first 40 natalizumab-treated MS patients diagnosed with PML in the postmarketing setting were identified, of whom 22 (10 with clinically diagnosed immune reconstitution inflammatory syndrome) fulfilled the inclusion criteria for this study. Magnetic resonance images were analyzed according to predefined criteria by 5 independent readers.
  
  
  RESULTS
  The most frequent lesion pattern in early scans from PML patients was that of large (>3 cm, 15 of 18), subcortical (18 of 18), T2 or fluid-attenuated inversion recovery hyperintense (18 of 18), T1-hypointense (17 of 18), and diffusion-hyperintense (15 of 15) lesions, with a sharp border toward the gray matter and an ill-defined border toward the white matter (18 of 18) on T2-weighted images. We could detect contrast enhancement in 41% (7 of 17) of the cases on the first scan at clinical presentation.
  
  
  CONCLUSIONS
  Attention to characteristic MRI patterns, especially the presence of contrast enhancement, and the subcortical location may have utility in screening and early diagnosis of PML in natalizumab-treated MS patients.
authors.affiliation: Lysholm Department of Neuroradiology, University College London Hospitals National Hospital for Neurology and Neurosurgery, and Academic Neuroradiological Unit, University College London Institute of Neurology, London, United Kingdom. t.yousry@ucl.ac.uk
authors.forename: Tarek A
authors.initials: TA
authors.lastname: Yousry
authors.forename: Daniel
authors.initials: D
authors.lastname: Pelletier
authors.forename: Diego
authors.initials: D
authors.lastname: Cadavid
authors.forename: Achim
authors.initials: A
authors.lastname: Gass
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Richert
authors.forename: Ernst-Wilhelm
authors.initials: EW
authors.lastname: Radue
authors.forename: Massimo
authors.initials: M
authors.lastname: Filippi
mesh_terms: D000328:Adult; D061067:Antibodies, Monoclonal, Humanized / Q000009:adverse effects*; D001921:Brain / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007968:Leukoencephalopathy, Progressive Multifocal / Q000139:chemically induced* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000188:drug therapy; D000069442:Natalizumab; D011358:Product Surveillance, Postmarketing; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000069442:Natalizumab