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[MRI aspects of progressive multifocal leukoencephalopathy]
J L Sarrazin1, D Soulié, C Derosier
1H.I.A du Val-de-Grâce, Paris.
Abstract:
Progressive Multifocal Leukoencephalopathy is a demyelinating disease. MRI shows high signal intensity areas on T2w sequence and low intensity aeras on T1w sequence, without enhancement after intravenous contrast injection. The involvement of arcuate fiber (U fibers) creates a sharp border with the cortex. There is no mass effect. Involvement of parieto-occipital areas is frequent. The lesions may be uni or bilateral, single or multiple; bilateral lesions are asymmetric. This typical appearance on MR images occurs in 90% of the patients with PML. Some atypical patterns may occur: focal hemorrhage, atrophy, faint peripheral enhancement and involvement of deep gray matter (basal ganglia). In most cases, the clinical and MR features provide the diagnosis. The main differential diagnosis, in MRI, is HIV-leukoencephalitis, but lesions are diffuse, less intense on T2w sequence and not visible on T1, without involvement of the arcuate fibers. Stereotactic biopsy should be performed only for atypical lesions, particularly in case of predominant involvement of deep gray structures.
Insights
Progressive Multifocal Leukoencephalopathy (PML) is a demyelinating disease diagnosed via characteristic MRI findings. Typical PML lesions show specific T1 and T2 signal changes, aiding differentiation from other conditions like HIV-leukoencephalitis.
Area of Science:
- Neurology
- Radiology
- Pathology
Context:
- Progressive Multifocal Leukoencephalopathy (PML) is a rare, severe demyelinating disease affecting the brain's white matter.
- Magnetic Resonance Imaging (MRI) is crucial for diagnosing neurological disorders, including PML.
Purpose:
- To describe the typical and atypical MRI features of Progressive Multifocal Leukoencephalopathy (PML).
- To differentiate PML from other white matter lesions, particularly HIV-leukoencephalitis, based on imaging characteristics.
Summary:
- PML is a demyelinating disease characterized by specific MRI findings: high T2w and low T1w signal intensity lesions without contrast enhancement.
- Typical lesions involve arcuate fibers (U-fibers) with a sharp cortical border, often in parieto-occipital areas, and lack mass effect.
- Atypical presentations include hemorrhage, atrophy, faint enhancement, or basal ganglia involvement, necessitating biopsy in ambiguous cases.
Impact:
- Accurate MRI interpretation aids in the timely diagnosis of PML, guiding clinical management.
- Understanding imaging patterns helps distinguish PML from mimics, optimizing patient care and avoiding unnecessary invasive procedures.