A 34 year-old man with HIV refused treatment with anti-viral treatment.  Over the course of 3 weeks, he developed progressive ataxia affecting the left side.

Axial Flair MRI of the Brainstem and Cerebellum - note the large area of abnormality affecting the left middle cerebellar peduncle and deep left cerebellum.  There is no mass effect on the nearby 4th ventricle.  This lesion is confined to the white matter.  This condition is known as Progressive Multifocal Leukoencephalopathy which results from an opportunistic infection from the JC virus.  This condition occurs in AIDS and other immunocompromised patients. It is recognized as a progressive, subacute process affecting the white matter without enhancement or mass effect on imaging studies. 

Revised 04/26/06.
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