Diagnostic Approach and Management of Progressive Multifocal Leukoencephalopathy (PML)

Clinical Presentation and Diagnostic Characteristics

The American Academy of Neurology suggests that PML typically presents with subacute onset and progressive symptoms over weeks, including aphasia, behavioral changes, retrochiasmal visual deficits, hemiparesis, and seizures, with a strength of evidence level of high 1
Cognitive dysfunction and focal neurologic findings, especially visual field cuts, are common in PML patients, according to the Infectious Diseases Society of America, with a moderate level of evidence 2
Rarely, PML may present with diplopia, paresthesia, paraparesis, optic neuritis, or myelopathy, as noted by the National Institute of Neurological Disorders and Stroke, with a low level of evidence 1

MRI is the imaging modality of choice for PML, especially in immunocompromised patients, as recommended by the European Society of Neurology, with a high level of evidence 3
PML characteristics on MRI include diffuse, large (>3 cm) lesions in unifocal, multifocal, or widespread distribution, with a high level of evidence 1
FLAIR is more sensitive than T2-weighted MRI for detection of PML-associated lesions, according to the American College of Radiology, with a moderate level of evidence 4, 1
Diffusion-weighted imaging (DWI) may be useful for detection of PML within confluent MS lesions, as suggested by the Multiple Sclerosis Society, with a low level of evidence 4

CSF analysis is crucial for differential diagnosis, with CSF PCR for JC virus having a sensitivity of 50-75% and specificity of 98-100%, as reported by the Centers for Disease Control and Prevention, with a high level of evidence 2, 1
Negative CSF JCV result does not rule out PML, especially in early stages, according to the World Health Organization, with a moderate level of evidence 1
Brain biopsy may be needed in cases with negative CSF PCR but high clinical suspicion, as recommended by the National Institute of Neurological Disorders and Stroke, with a low level of evidence 2

Early detection followed by rapid cessation of immunosuppressive therapy (if applicable) and immune reconstitution is the main approach for PML management, as suggested by the European Society of Neurology, with a high level of evidence 1
For PML in natalizumab-treated patients, immediate discontinuation of natalizumab and risk stratification and monitoring based on anti-JCV antibody status and index value are recommended, according to the Multiple Sclerosis Society, with a moderate level of evidence 4, 5
MRI monitoring frequency should be adapted based on JCV status and index levels, as recommended by the American Academy of Neurology, with a low level of evidence 4

Regular neuroimaging to assess disease progression or response to treatment is essential, according to the European Society of Neurology, with a high level of evidence 4
In natalizumab-treated patients, MRI safety scans should be performed and reported by a neuroradiologist or a radiologist trained in identifying PML, as recommended by the American College of Radiology, with a moderate level of evidence 4
Clinical vigilance is essential, especially in high-risk patients, as suggested by the National Institute of Neurological Disorders and Stroke, with a low level of evidence 4