Cognitive Impairment and Dementia
Distinguishing the three Ds
Delirium is acute, fluctuating, and inattentive; dementia is chronic and progressive; depression can mimic dementia ("pseudodementia") with apathy and poor effort. Delirium frequently superimposes on dementia, and the single best question is whether cognition changed acutely. Screen with the Mini-Cog or MoCA, then obtain targeted laboratory studies (TSH, B12, CBC, chemistry, calcium), review medications with anticholinergic burden, and image only if focal findings, rapid decline, or atypical features are present.
Dementia subtypes
Alzheimer disease: insidious episodic memory loss, then language and visuospatial decline. Vascular dementia: stepwise course, executive and gait involvement, vascular risk factors. Dementia with Lewy bodies: fluctuating attention, recurrent well-formed visual hallucinations, parkinsonism, REM sleep behavior disorder, and severe sensitivity to typical antipsychotics - avoid haloperidol; cholinesterase inhibitors help hallucinations. Frontotemporal dementia: personality change, disinhibition, hyperorality, or progressive aphasia with relative sparing of memory and visuospatial function. Normal pressure hydrocephalus: the "wacky, wobbly, wet" triad of cognitive decline, gait apraxia, and incontinence.
Treatment and counseling
Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) for mild-to-moderate Alzheimer disease; memantine for moderate-to-severe. Monitor for bradycardia, syncope, GI upset, and weight loss. Nonpharmacologic behavioral approaches come first for agitation. Address driving, firearms, financial capacity, caregiver burden, and advance care planning early.
Traps
Treating delirium with antipsychotics before finding the cause; missing urinary retention, constipation, or a new medication as delirium triggers; labeling depression as dementia without cognitive re-testing after treatment.
Rule of thumb
Acute change equals delirium until proven otherwise - hunt for triggers rather than titrating donepezil.