Question category: Neurology
A 37 year old male with HIV is brought to A+E with a 6 week history of behavioural and personality change. On examination there is evidence of conjugate gaze abnormality and ataxia. There is also left arm weakness. An MRI is performed and reveals on T2 weighted images multiple bilateral hyperintense lesions predominantly in periventricular and subcortical white matter. What is the most likely diagnosis?