Inflammatory natalizumab-associated PML: baseline characteristics, lesion evolution and relation with PML-IRIS

Area of Science:

• Neuroimaging
• Immunology
• Infectious Diseases

Background:

• Natalizumab-associated progressive multifocal leukoencephalopathy (NTZ-PML) can present with imaging signs of inflammation at diagnosis.
• These inflammatory signs resemble those seen in PML-immune reconstitution inflammatory syndrome (PML-IRIS).
• Investigating these imaging features is crucial for understanding disease progression and response.

Purpose of the Study:

• To compare the imaging characteristics of inflammatory NTZ-PML lesions at diagnosis with those of PML-IRIS.
• To identify differentiating and overlapping features between inflammatory NTZ-PML and PML-IRIS on MRI.
• To elucidate the underlying pathophysiology of inflammation in NTZ-PML and PML-IRIS.

Main Methods:

• Brain MRI scans of NTZ-PML patients were analyzed for inflammatory characteristics.
• Presence, localization, and pattern of inflammation were scored.
• Imaging features were tracked from diagnosis through the PML-IRIS stage.

Main Results:

• Ten of 44 NTZ-PML patients exhibited inflammation at diagnosis.
• Inflammation patterns at diagnosis and PML-IRIS were similar, with contrast enhancement being frequent (90% vs 100%).
• Inflammation severity differed, with less swelling and edema at diagnosis (10%) compared to PML-IRIS (40%).

Conclusions:

• Inflammation patterns in NTZ-PML and PML-IRIS overlap but vary in severity.
• This supports shared pathophysiology, indicating an immune response to JC virus.
• Imaging findings aid in understanding the inflammatory process in NTZ-PML and its evolution.