You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is An elderly man with history of frequent falls presents to ED with features of dementia, ataxia, difficulty in downward gaze. What is the most likely diagnosis? and explain in detail?
Progressive supranuclear palsy (PSP) is a degenerative disease that involves the brainstem, basal ganglia, limbic structures and selected areas of coex. Clinically, this disorder begins with falls and executive or subtle personality changes such as mental rigidity, impulsivity, or apathy. A progressive oculomotor syndrome ensues that begins with square wave jerks, followed by slowed saccades (veical worse than horizontal) before resulting in progressive supranuclear ophthalmoparesis. Dysahria, dysphagia, and symmetric axial rigidity can be prominent features that emerge at any point in the illness. A stiff, unstable posture with hyperextension of the neck and a slow, jerky, toppling gait is characteristic. The oculomotor disorder is supranuclear.The dementia overlaps with Fronto temporal dementia, featuring apathy, frontal-executive dysfunction, poor judgment, slowed thought processes, impaired verbal fluency and difficulty with sequential actions and with shifting from one task to another. Response to l-dopa is limited or absent. Death occurs within 5-10 years of onset. Ref: Harrison's Internal Medicine, 18th Edition, Pages 3311, 3317-3326, 3309, 3305