Alzheimer Disease: Symptoms, Course, and Pathology
Alzheimer disease is a neurodegenerative disorder characterized by progressive impairment of shortterm memory and other memory, language, and thought processes. Functions are typically lost in the reverse order in which they were attained. In advanced stages, patients cannot perform simple activities of daily life. Diagnosis is usually made 3 years or more after symptom onset, and life expectancy is approximately 7 to 10 years after diagnosis. Gross brain atrophy accompanies the progression of the disease, with characteristic high numbers of neuritic plaques (fragments of insoluble amyloid, type Aβ, protein) and neurofibrillary tangles (abnormal τ microtubule complexes), particularly in the hippocampus and posterior temporoparietal lobe areas. Predisposing factors include aging and genetics, with a possible contribution from environmental toxins. The neurodegeneration results in loss or dysfunction of neurotransmitter pathways.