Organic and Neuropsychiatric Disorders
Core concepts
Delirium is acute, fluctuating, with impaired attention and altered awareness; identify causes (infection, drugs, metabolic, hypoxia, withdrawal) using a systematic approach. Dementia subtypes: Alzheimer's (amyloid/tau, medial temporal atrophy), vascular (stepwise, focal signs), Lewy body (fluctuating cognition, visual hallucinations, parkinsonism, neuroleptic sensitivity), frontotemporal (behavioural/personality change, language variants). Know epilepsy-related psychiatric phenomena: pre-ictal, ictal, post-ictal psychosis, and interictal personality features (especially temporal lobe). Head injury: concussion, post-concussive syndrome, and risk of subsequent psychiatric disorder. Substance-related organic states: alcohol withdrawal (delirium tremens, timing 48-96 hours), Wernicke's encephalopathy (triad: confusion, ataxia, ophthalmoplegia - give thiamine before glucose), Korsakoff's amnesic syndrome.
Traps
Lewy body dementia patients are exquisitely sensitive to antipsychotics - avoid or use minimal doses. Delirium is often hypoactive and missed. Wernicke's is a medical emergency; never give glucose first without thiamine. Distinguish delirium from dementia (delirium = acute, fluctuating, attentional; dementia = chronic, progressive).
Rule of thumb
Any acute change in mental state in an older or medically ill patient is delirium until proven otherwise - search for a cause.