Topic overview

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Alzheimer disease is the most common cause of dementia and is associated with extracellular amyloid-β plaques, intracellular hyperphosphorylated tau tangles, and atrophy of the cortex and hippocampus. Its clinical course typically begins with gradual memory loss and may progress to impairments in language, visuospatial function, and executive function. The lesson also covers genetic associations, structural and microscopic findings, biomarkers, diagnosis, and treatment approaches. Parkinson disease is a progressive hypokinetic movement disorder linked to dopaminergic neuron loss in the nigrostriatal pathway and α-synuclein Lewy bodies. Its motor features include resting tremor, rigidity, bradykinesia, and postural instability. Non-motor features, related disorders, risk factors, and pharmacologic management are also addressed.