Clinical meaning
Dementia is a chronic, progressive syndrome characterized by deterioration of cognitive function beyond what is expected from normal aging. Unlike delirium, which develops acutely and is typically reversible, dementia has a gradual onset and is generally irreversible. The most common type is Alzheimer disease (AD), accounting for 60-70% of all dementia cases. In Alzheimer disease, two hallmark pathological changes occur in the brain: extracellular amyloid-beta plaques and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. Amyloid-beta protein, which is normally produced and cleared from the brain, accumulates into insoluble plaques between neurons when the balance between production and clearance is disrupted. These plaques trigger an inflammatory response, activate microglia (the brain's immune cells), and generate oxidative stress that damages surrounding neurons. Simultaneously, tau protein, which normally stabilizes microtubules within neurons to maintain structural integrity and axonal transport, becomes hyperphosphorylated. This hyperphosphorylated tau detaches from microtubules, aggregates into paired helical filaments, and forms neurofibrillary tangles inside neurons. The tangles disrupt intracellular transport, leading to synaptic dysfunction and eventual neuronal death. The disease typically begins in the hippocampus and entorhinal cortex (explaining early memory loss) and progressively spreads to the temporal, parietal, and frontal lobes. Vascular dementia is the second most common type, caused by reduced blood flow to the brain from cerebrovascular disease. Unlike the gradual decline of Alzheimer disease, vascular dementia often presents with a stepwise deterioration pattern, where cognitive function declines abruptly after each vascular event (stroke or transient ischemic attack) and then stabilizes until the next event. Risk factors mirror those for cardiovascular disease: hypertension, diabetes, hyperlipidemia, atrial fibrillation, and smoking. Lewy body dementia (LBD) is characterized by abnormal protein deposits called Lewy bodies (alpha-synuclein aggregates) within neurons throughout the cortex. LBD presents with fluctuating cognition, recurrent visual hallucinations, and parkinsonism (rigidity, bradykinesia, postural instability). A critical clinical distinction is that patients with LBD have extreme sensitivity to antipsychotic medications, which can cause severe neuroleptic malignant syndrome and death. Frontotemporal dementia (FTD) involves degeneration of the frontal and temporal lobes, presenting primarily with personality changes, behavioral disinhibition, and language difficulties rather than the memory loss seen in Alzheimer disease. The practical nurse plays a critical role in person-centered dementia care, which focuses on maintaining the individual's dignity, preferences, abilities, and quality of life rather than focusing solely on deficits. Standardized cognitive screening tools include the Mini-Mental State Examination (MMSE) with a maximum score of 30 (scores below 24 suggest cognitive impairment) and the Montreal Cognitive Assessment (MoCA), which is more sensitive for detecting mild cognitive impairment.