Fact-sheet: Progressive multifocal leukoencephalopathy
Updated on 09/26/2024 at 10:09 AM
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Definition
Subacute demyelinating infection of the CNS related to reactivation of a papovavirus, the JC virus, usually non-pathogenic.
It occurs in a setting of profound immunosuppression (HIV) or during treatment with NATALIZUMAB (Tysabri: second-line treatment for MS).
Clinical features
Nonspecific.
An isolated, progressive focal neurological deficit is usually found, with good radio-clinical correlation
Laboratory findings
JC virus testing in CSF by PCR
JC virus serology is recommended semiannually as part of NATALIZUMAB treatment in patients with MS
Definitive diagnosis remains histological
MRI
Reference examination.
Demyelinating lesions are found:
- in the subcortical white matter
- bilateral and asymmetric
- sparing the gray matter and spinal cord
- supratentorial (parieto-occipital, frontal) and infratentorial in location
- with involvement of the basal ganglia and subcortical U-fibers
- hypointense on T1 and hyperintense on T2
- without mass effect
- Classically without enhancement after gadolinium injection. Contrast enhancement is suggestive of an inflammatory form of PML or occurs in a setting of immune restoration.
Milky Way sign: punctate, ill-defined T2-FLAIR hyperintensities at the periphery of white matter demyelinating lesions.
A decrease in ADC values at the periphery of the lesions is noted in active lesions (demyelinating front).
Management
No specific treatment available
Early and rapid immune restoration reduces the risk of progression
The outcome is fatal in approximately 30% of cases
Differential diagnosis
The milky way sign is also described in CLIPPERS (Chronic Lymphocytic Inflammation with Pontine Perivascular Enhancement Responsive to Steroids), but in this condition involvement is limited to the brainstem.