Geriatric Psychiatry: Cognitive Disorders, Assessment, and Treatment
Core concepts
Geriatric psychiatry questions reward precise definitions. Know the DSM-5-TR neurocognitive disorder (NCD) framework: major vs. mild NCD is separated by whether deficits interfere with independent everyday function, not by the severity of a single test score. Know the common dementia syndromes and their signature profiles: Alzheimer disease (insidious amnestic onset, temporoparietal/hippocampal atrophy), vascular NCD (stepwise course, executive/speed deficits, cerebrovascular disease), dementia with Lewy bodies (fluctuating cognition, formed visual hallucinations, parkinsonism, REM sleep behavior disorder, neuroleptic sensitivity), frontotemporal dementia (behavioral disinhibition or language-predominant variants with relatively preserved memory), and normal-pressure hydrocephalus (gait apraxia, incontinence, cognitive slowing).
Assessment
Screen with a validated instrument (MMSE, MoCA, Mini-Cog) but never diagnose from a screen alone; obtain informant-based functional history (e.g., FAQ, ADL/IADL) and formal testing. Order reversible-cause workup: CBC, CMP, TSH, B12, and neuroimaging when focal signs, rapid decline, or atypical features are present. Always assess depression (pseudodementia pattern), delirium (acute onset, fluctuating attention), and sensory/medication contributors.
Treatment and traps
Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine are symptomatic; they do not reverse disease. Watch for bradycardia, GI upset, weight loss, and syncope. Avoid antipsychotics in dementia except for severe agitation or psychosis, at the lowest dose and shortest duration, given elevated mortality and cerebrovascular risk; avoid typical antipsychotics in Lewy body disease. Traps: equating a low MMSE with major NCD without functional data; forgetting that delirium is a medical emergency and that depression can mimic dementia.
Rule of thumb: the diagnosis hinges on function, the workup hinges on reversibility, and the treatment hinges on symptom targets and safety.