A 67-year-old man is brought in by his son, who is deeply concerned by his father’s sudden onset of ataxia, myoclonus, and neurocognitive defects. Diffusion weighted MRI identifies multifocal gray matter hyperintensities in the subcortical and cortical regions. An EEG reveals slow, symmetric sharp spikes. What is the most likely diagnosis?

Choice A reason: Lewy body dementia presents with cognitive fluctuations, visual hallucinations, and parkinsonism, but the acute onset of myoclonus and multifocal MRI findings are not typical. Choice B reason: Alzheimer’s disease presents with gradual cognitive decline rather than sudden onset of ataxia and myoclonus, making it less likely. Choice C reason: Huntington’s disease is a hereditary neurodegenerative disorder with chorea, psychiatric symptoms, and gradual cognitive decline, not acute multifocal neurologic deficits. Choice D reason: Sporadic Creutzfeldt-Jakob disease is a prion disease characterized by rapidly progressive dementia, myoclonus, ataxia, and characteristic MRI and EEG findings, matching this patient’s presentation.