Progressive Multifocal Leukoencephalopathy: MRI

Case Report: 43 y Male, known retroviral  status with altered sensorium for MRI shows-

Diffuse non-enhancing  T2 and FLAIR white matter hyperintensity in supratentorial white matter in all the lobes, middle cerebellar peduncles, right thalamus, corpus callosum  with mild mass effect over sulcal spaces & ventricles with subtle bright signal in DWI with sparing of grey matter & subcortical U fibers with unremarkable flow voids, dural sinuses,optic chiasm/intraventricular extension, midline extension. Prominent subependymal vessels & pachymeninges seen on contrast without nodularity. These findings are likely suggestive of progressive multifocal leukoencephalopathy, in view of retroviral status.

Teaching Points by Dr MGK Murthy , Dr GA Prasad, MR Tech Sudhakar 

Demyelinating disease  of CNS caused by reactivation of JC virus in immunocompromised pts. Typically seen in AIDS, transplant recepients, leukemia, in association with natalizumab treatment for Crohn disease and multiple sclerosis, monoclonal therapies.   80% of adults have anti JC antibodies normally.

Definitive diagnosis of PML requires neuropathologic demonstration of the typical histopathologic triad (demyelination, bizarre astrocytes, and enlarged oligodendroglial nuclei) coupled with the techniques to show the presence of JC virus. The presence of clinical and imaging manifestations consistent with the diagnosis and not better explained by other disorders coupled with the demonstration of JC virus by PCR in CSF is also considered diagnostic.

Symptoms – general weakness, gait disturbance, visual disturbance (optic radiation involvement), seizures, cognitive dysfunction. In AIDS pts. CD4 counts are usually less than 100 cells/microL.

MRI- The lesions of PML are hyperintense on T2/FLAIR images  & T1  iso to hypointense   may occur virtually anywhere in the brain & are characteristically multifocal without significant mass effect.  Asymmetric monofocal  frontal or parieto-occipital lobe lesions also common, frequently large (>3 cm), subcortical with sharp border toward the cortex and ill-defined border toward the white matter on T2-weighted image. About 15% of patients with HIV-associated PML may show gadolinium enhancement on MRI. Isolated or associated involvement of the basal ganglia, external capsule, and posterior fossa structures (cerebellum and brainstem) may be seen as well. DD- based on location – low grade glioma / infarct/ MS/ small vessel ischemic changes (CADASIL), gliomatosis cerebri

DD- HIV encephalopathy – diffuse corticocerebral atrophy – significant for the age, T2 hyperintese bilateral symmetric frontoparietal periventricular white matter lesions.