Pathophysiology
Clinical meaning
Delirium and dementia are distinct neurological conditions that share overlapping clinical features but differ fundamentally in pathophysiology, onset, course, and reversibility. The NP must differentiate these conditions because management differs dramatically. Delirium is an acute, fluctuating disturbance in attention and cognition caused by an identifiable physiological insult. The neurotransmitter imbalance hypothesis identifies decreased acetylcholine and increased dopamine as the primary drivers. Systemic inflammation (from infection, surgery, or metabolic derangement) releases pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) that cross the blood-brain barrier and activate microglia, causing neuroinflammation that disrupts synaptic transmission. Anticholinergic medications exacerbate this by further depleting already-compromised cholinergic signaling. The oxidative stress hypothesis proposes that impaired cerebral oxidative metabolism reduces neurotransmitter synthesis. Delirium is typically reversible when the precipitating cause is identified and treated. Dementia is a chronic, progressive neurodegenerative process. In Alzheimer disease (most common, 60-70%), extracellular amyloid-beta plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau protein accumulate, causing synaptic dysfunction and neuronal death. Cholinergic neurons in the nucleus basalis of Meynert are among the first affected, producing the memory deficits characteristic of early Alzheimer. Vascular dementia (15-20%) results...