Clinical meaning
Delirium and dementia are the two most important cognitive disorders in clinical nursing. DELIRIUM is an acute, reversible disturbance in attention and awareness with fluctuating course, caused by an underlying medical condition. It is a MEDICAL EMERGENCY because it signifies an acute physiological derangement. The pathophysiology involves widespread cortical dysfunction from cholinergic deficiency (explaining why anticholinergic medications are a major cause), dopaminergic excess, neuroinflammation (cytokines cross the blood-brain barrier during systemic illness), oxidative stress, and disruption of the sleep-wake cycle. DEMENTIA (now termed Major Neurocognitive Disorder in DSM-5) is a chronic, progressive, generally irreversible decline in cognitive function affecting memory, language, executive function, and daily functioning. Alzheimer disease (AD, 60-70% of dementia) involves amyloid-beta plaque accumulation outside neurons and tau protein neurofibrillary tangle formation inside neurons, leading to synaptic loss and neuronal death, particularly in the hippocampus (memory) and temporal/parietal cortices. Vascular dementia (15-20%) results from cerebrovascular disease (strokes, chronic small vessel disease). Lewy body dementia involves alpha-synuclein protein deposits causing cognitive fluctuation, visual hallucinations, and parkinsonism. Frontotemporal dementia affects personality and language before memory. The critical nursing distinction: delirium...