Article Text

Download PDFPDF
WED 170 The utility of brain FDG-PET in a patient with natalizumab associated PML-IRIS
  1. Baheerathan Aravindhan,
  2. Kalam Sabrina,
  3. Grote Helen,
  4. Mcnamara Cillian,
  5. Rane Neil,
  6. Nicholas Richard
  1. Imperial College London
  2. *Joint first authors


Natalizumab, a highly effective disease modifying drug used in relapsing remitting multiple sclerosis (RRMS), is associated with progressive multifocal leukoencephalopathy (PML), a fatal intracerebral demyelinating disease caused by the JC virus that can be worsened with concurrent use of steorids. Stopping natalizumab in the context of PML can cause immune reconstitution inflammatory syndrome (IRIS) that can be treated with steroids. IRIS can be indistinguishable from PML on MRI - thus causing a clinical conundrum.

We describe a woman with RRMS on Natalizumab who developed dysarthria and right-sided hemiparesis. MRI demonstrated non-enhancing peridentate white matter signal abnormality in the right middle cerebellar peduncle (RMCP). Cerebrospinal fluid JC virus DNA was >1 million copies/ml. PML was diagnosed and Natalizumab withdrawn. Four weeks later she developed bulbar weakness and left-sided hemiparesis despite falling JC virus DNA. Repeat MRI demonstrated new extensive pontine changes consistent with PML-IRIS.

FDG-PET imaging confirmed focal areas of hypometabolism at the original site of PML and multiple areas of hypermetabolism in the left pons and middle cerebellar peduncle, suggestive of IRIS. Her clinical deterioration was attributed to IRIS and Prednisolone was commenced.

In this case FDG-PET scanning helped distinguish between PML and IRIS, guiding patient management.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.