Neurocognitive, Organic and Consultation-Liaison Psychiatry
Core concepts
Differentiate delirium (acute onset, fluctuating, impaired attention, perceptual disturbance) from dementia (chronic progressive cognitive decline with preserved consciousness) and depression (pseudodementia). Know the major dementia subtypes: Alzheimer's (memory first), vascular (stepwise, focal signs), Lewy body (fluctuations, visual hallucinations, parkinsonism, neuroleptic sensitivity), frontotemporal (behaviour/personality or language first).
Consultation-liaison
Recognise psychiatric presentations of medical illness: hyperthyroidism (anxiety), hypothyroidism (depression), Cushing's (depression/psychosis), SLE (psychosis), porphyria, Wilson's disease, and medication effects (steroids, interferon, anticholinergics). Assess capacity using the four-stage test: understand, retain, weigh, communicate.
Traps
- Missing delirium in an older patient with new behavioural change - always check attention and use 4AT/CAM.
- Prescribing antipsychotics in Lewy body dementia (severe sensitivity).
- Attributing cognitive decline to depression without formal testing.
- Failing to consider serotonin syndrome in patients on multiple serotonergic agents.
Rule of thumb
In any older patient with acute confusion, treat as delirium until proven otherwise and search for the cause (infection, drugs, metabolic, retention, pain).