In this video the viewer can learn the basic pathogenesis of JC virus associated with PML, population at risk, imaging findings seen on CT and MRI scans and treatment trials that are done. All this information is provided in the form of flow charts. Timeline: 0:00 - Pathogenesis of PML 1:51 - Clinical features 2:23 - Population at risk 4:05 - Imaging findings and diagnosis of PML 5:17 - Treatment trials