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Progressive white matter lesion in the frontoparietal lobes
Active large lesion (acute progression) of fused small demyelinating lesions.
Precentral gyrus and surrounding area.
Cortical gray matter involvement.
Juxtacortical/subcortical white matter involvement.
Extension to the deep white matter, partially toward the corpus callosum.
Expansion and fusion of lesions with destruction of neuronal axons.
Presence of JCV‐infected glial cells in the frontiers of extending or expanding lesions.
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Central lesion including deep gray matter
Active lesion (subacute progression) in the left thalamus.
Inactive lesion in the right thalamus, putamen and claustrum.
Contiguous extension from the pontine tegmentum to the left lateral thalamus.
Involvement of the reticular formation and trigeminothalamic tract.
Preservation of medial longitudinal fasciculus and oculomotor nucleus.
Neuronal cell death in the putamen, thalamus, red nucleus, and substantia nigra.
Thalamic neurons with central chromatolysis and spheroid structures.
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Infratentorial lesion of brainstem and cerebellum
Active lesion (subacute progression) involving middle cerebellar peduncles.
Extension in pontocerebellar fibers, longitudinal fibers, and cerebellar white matter.
Neuronal cell death in the pontine nuclei and the cerebellar dentate nucleus.
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Satellite lesions all over the brain
(1) Small demyelinating lesions around the corticomedullary borders.
(2) Early and small demyelinating lesions in deep white matter.
Perivascular edema and parenchymal edema seen as myelin pallor.
Resemblance to “starry” or “Milky Way” features on MRI.
