<prompt> A 54 year old white male presents with gradual onset of mild dementia, ataxic gait, and stale myoclonus. An MRI scan is normal, and an examination of his cerebrospinal fluid reveals no abnormalities, but the patients EEG is remarkable for recurrent bursts of high-voltage slow waves. Over the next 6 months, the patients dementia rapidly worsens, accompanied by general hypeonicity and profound dysahria. The patient dies sholy thereafter. Which of the following is the mostly likely neuropathological finding on autopsy?Cerebellar hyperplasiaDiffuse spongiform changeMultiple lacunar infarctsNegri bodies  <response>: The rapidly progressive dementia in this case is characteristic of Creutzfeldt-Jakob disease CJD. The dementia is usually accompanied by motor dysfunction and abnormal EEG activity, as described in the question stem. The pathological hallmark of this disease is spongiform change in the gray matter. Death usually occurs within 6-12 months of disease onset. At autopsy, the cerebellum in CJD appears atrophic, not hyperplastic. Multiple lacunar infarcts are seen with vascular dementia, and patients typically present with focal neurological signs. Additionally, vascular dementia typically presents with a more gradual decline in cognitive function, measured in years rather than months. Negri bodies are pathognomonic for rabies, which does not cause dementia. Ref: Ropper A.H., Samuels M.A. 2009. Chapter 33. Viral Infections of the Nervous System, Chronic Meningitis, and Prion Diseases. In A.H. Ropper, M.A. Samuels Eds, Adams and Victors Principles of Neurology, 9e. 