Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Distinguish mild cognitive impairment from dementia and delirium using collateral functional evidence, adapt cognitive testing to language and sensory needs, identify reversible contributors, and reach a defensible subtype through specialist assessment and imaging.
Cognitive assessment should answer three separate questions: is there an acquired decline, does it impair independence, and what is the likely cause or subtype? Memory, executive function, attention, language, visuospatial ability and social cognition may be affected in different proportions. Alzheimer disease often starts with episodic memory impairment, vascular disease may emphasise executive speed and gait, Lewy body disease brings fluctuation and visuoperceptual symptoms, and frontotemporal disease may start with behaviour or language. Mixed pathology is common, particularly later in life.
Collateral history is not a vote against the patient. It provides examples of change, while the patient’s account establishes concerns, values and insight. Speak separately when appropriate and consented, and consider coercion or safeguarding. Functional decline should be separated from arthritis, visual loss, poverty, lack of opportunity or a partner who has always managed tasks. A decision-specific capacity assessment is required when choices are questioned; a diagnosis or low test score does not make someone globally incapable.
Concern plus objective decline with preserved independence in most daily activities supports MCI after delirium and treatable contributors are considered, but longitudinal review is needed.
Progressive cognitive change that causes medication errors, unsafe cooking, lost travel, financial failure or dependence in instrumental activities supports major functional impact.
Hours-to-days onset, fluctuation, impaired attention and altered arousal in an acutely ill person indicates delirium even when chronic neurodegeneration increases vulnerability.
Low mood, anhedonia, slowed thinking, sleep change and prominent subjective concern may impair cognition, but depression and neurodegeneration can coexist and both require follow-up.
Presentation before 65, rapid progression, seizures, neurological signs, early language or behavioural syndrome or strong family history warrants expedited specialist and sometimes tertiary assessment.
Do not abruptly stop benzodiazepines, gabapentinoids, antidepressants or necessary psychiatric treatment. Balance recurrence of the treated condition, involve the original prescriber and monitor after each change.
MCI can represent early neurodegeneration, so absence of medication is not absence of care. Arrange risk-factor work, support and longitudinal reassessment, and use biomarkers only through appropriate services.
The distinction between MCI and dementia depends substantially on interference with independent life, not a universal number on a cognitive screen.
A highly educated person may compensate on a brief screen despite major workplace change, while language or education can depress scores without neurodegeneration.
An acute delirium may reveal previously unrecognised cognitive impairment, but definitive baseline assessment is usually more reliable after the acute syndrome improves.
Informant evidence is valuable but can contain conflict or coercion, so clinicians should seek permission, preserve the patient’s voice and assess safeguarding.
A person may lack capacity for one complex financial decision while retaining capacity for daily care choices and treatment preferences.
Diagnosing dementia from a single low cognitive score ignores delirium, language, education, hearing and function.
Reassuring from one normal brief screen can miss executive, visuospatial or high-premorbid-ability decline supported by collateral evidence.
Calling acute inattention a dementia progression delays treatment of infection, hypoxia, medication toxicity or another delirium cause.
Ordering specialist biomarkers before basic history, function, bloods and structural imaging uses advanced tests without a clear clinical question.
Assuming a diagnosis removes all capacity or driving rights replaces individual legal assessment with stigma.
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A 73-year-old reports gradually worsening memory over 18 months. Which initial approach best follows NICE principles before deciding a dementia subtype?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes