Cognitive Disorders and Dementia
What to know
Dementia is progressive cognitive decline affecting function. Key types: Alzheimer disease (amnestic, insidious), vascular (stepwise, focal deficits), Lewy body (fluctuating cognition, visual hallucinations, parkinsonism, REM behavior disorder, neuroleptic sensitivity), and frontotemporal (behavior/personality or language). Use structured cognitive testing (Mini-Cog, MoCA, MMSE) plus functional assessment to establish dementia versus mild cognitive impairment. Always exclude reversible contributors: depression (pseudodementia), B12/thyroid, medications, sleep, delirium, and normal pressure hydrocephalus (gait apraxia, incontinence, cognitive decline).
Traps
Don't label delirium as dementia; acute change is delirium until proven otherwise. Lewy body patients are exquisitely sensitive to antipsychotics-avoid or use cautiously. Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) help mild-moderate Alzheimer; memantine for moderate-severe. Beware bradycardia, GI upset, and weight loss. Driving, capacity, and caregiver burden are frequently tested. Distinguish capacity (decision-specific) from competence (legal).
Rule of thumb
"Reversible before degenerative": check depression, B12, thyroid, medications, and delirium triggers before accepting an irreversible diagnosis.
Worked example
A 78-year-old has fluctuating confusion, visual hallucinations, and falls. Lewy body dementia is suspected. Avoid typical antipsychotics (severe sensitivity); consider a cholinesterase inhibitor, and review for delirium triggers.
Worked example 2
A patient with moderate Alzheimer and bradycardia on donepezil: consider dose adjustment and ECG monitoring.