Which statement best describes the imaging appearance of PML lesions on MRI?

Which statement best describes the imaging appearance of PML lesions on MRI?

• A. Non-enhancing or minimally enhancing demyelinating lesions with little mass effect.
• B. Ring-enhancing lesions with large edema.
• C. Isolated thalamic involvement.
• D. Diffuse cortical atrophy.

Answer: (A)

PML lesions on MRI are demyelinating foci that occur in immunocompromised patients, and they classically appear as multifocal subcortical white-matter abnormalities that are hyperintense on T2/FLAIR. They typically do not enhance with gadolinium and produce little to no mass effect. This non-enhancing, subtle-contrast pattern reflects active demyelination rather than a bulky tumor or abscess, helping distinguish PML from ring-enhancing lesions with edema (which suggest infection or tumor), isolated thalamic involvement (PML usually involves subcortical white matter rather than being confined to deep gray structures), or diffuse cortical atrophy (which is a nonspecific degenerative change).

PML lesions on MRI are demyelinating foci that occur in immunocompromised patients, and they classically appear as multifocal subcortical white-matter abnormalities that are hyperintense on T2/FLAIR. They typically do not enhance with gadolinium and produce little to no mass effect. This non-enhancing, subtle-contrast pattern reflects active demyelination rather than a bulky tumor or abscess, helping distinguish PML from ring-enhancing lesions with edema (which suggest infection or tumor), isolated thalamic involvement (PML usually involves subcortical white matter rather than being confined to deep gray structures), or diffuse cortical atrophy (which is a nonspecific degenerative change).