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Updated: Apr 27, 2026
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Published on: December 4, 2011
Progressive multifocal leukoencephalopathy: a rare cause of cerebellar edema and atypical mass effect. A case report
Chris Ojeda1, Rachid Assina2, Maureen Barry3
1Biomedical Engineering, Rutgers New Jersey Medical School; Newark, NJ, USA - gandhich@njms.rutgers.edu.
Abstract:
Progressive multifocal leukoencephalopathy (PML) is an opportunistic demyelinating disease of the CNS caused by the JC papovavirus (JCV). Demyelination due to oligodendrocyte death leads to multifocal, asymmetric lesions. MRI is a valuable tool for detecting and differentiating PML from other neuropathies. Radiographically, PML classically presents as bilateral, subcortical white matter lesions with a lack of brain atrophy. As the disease progresses, lesions become larger and coalesce to become confluent. Minor edema and mass effect are infrequently described and the presence of significant mass effect suggests an alternative diagnosis. In our case, a patient demonstrated atypical marked infratentorial mass effect. Bilaterally, cerebellar lesions with associated mass effect were observed, as well as effacement of cerebellar folia and partial effacement of the fourth ventricle. The diagnosis of PML was confirmed with a biopsy of the right cerebellar lesion showing classic PML histology, with JCV DNA detection by polymerase chain reaction in the biopsy material.
Insights
Progressive multifocal leukoencephalopathy (PML), a CNS disease from JC virus, typically shows subcortical lesions. This case highlights atypical PML with significant infratentorial mass effect, confirmed by biopsy.
Area of Science:
- Neuroscience
- Infectious Diseases
- Radiology
Background:
- Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system (CNS).
- It is caused by the opportunistic JC papovavirus (JCV) and leads to oligodendrocyte death.
- Magnetic Resonance Imaging (MRI) is crucial for diagnosing PML and differentiating it from other neuropathies.
Observation:
- Classically, PML presents as bilateral, subcortical white matter lesions without brain atrophy.
- Lesions tend to enlarge and coalesce as the disease progresses.
- Significant mass effect is uncommon and may suggest alternative diagnoses.
Findings:
- This case report details a patient with atypical PML exhibiting marked infratentorial mass effect.
- MRI revealed bilateral cerebellar lesions with associated mass effect, effacing cerebellar folia and the fourth ventricle.
- Histopathological analysis and JCV DNA detection via PCR confirmed the PML diagnosis.
Implications:
- This case underscores the importance of considering PML even with atypical presentations like significant mass effect.
- It emphasizes the diagnostic value of MRI combined with biopsy confirmation in complex cases.
- Understanding atypical PML presentations aids in timely diagnosis and management of this severe opportunistic infection.
