Delirium & Neurocognitive Disorders
A high-yield STEP 2 CK psychiatry lesson on delirium and DSM-5 neurocognitive disorders, covering diagnostic criteria and durations, subtype buzzwords, and next-best-step management with board-style vignettes.
The Neurocognitive Spectrum
Delirium and neurocognitive disorders (NCDs) are both acquired cognitive impairment, but boards hinge on one split: acute vs chronic. Delirium is an acute, fluctuating disturbance of attention and awareness driven by an underlying medical insult — a medical emergency that is often reversible once the cause is fixed. DSM-5 retired the word dementia, replacing it with major NCD (impairment severe enough to lose independence) and mild NCD (decline present, independence preserved).
The two axes examiners test are:
- Onset & course — hours-to-days and waxing/waning → delirium; months-to-years and steadily progressive → NCD.
- Attention — grossly impaired in delirium, relatively spared early in dementia.
Critically, delirium is frequently superimposed on dementia (a demented brain is the single biggest risk factor), so a sudden change in a known dementia patient is delirium until proven otherwise.
- Delirium: disturbance in attention + awareness developing over hours to days, fluctuating through the day, plus a change in cognition (memory, orientation, perception); caused by a medical condition, substance, or withdrawal.
- Subtypes: hyperactive (agitated, hallucinating), hypoactive (quiet, drowsy — most common in elderly, most missed, worse prognosis), mixed.
- Major NCD: significant decline in ≥1 domain (complex attention, executive function, learning/memory, language, perceptual-motor, social cognition) that interferes with independence (needs help with IADLs).
- Mild NCD: modest decline that does NOT compromise independence (extra effort/compensation only).
- Key line: the mild-vs-major cut = loss of functional independence, not a memory-test score.
- NCD is not diagnosed if deficits occur only during delirium.
- Alzheimer disease = most common major NCD (~60–80%); hallmark = insidious short-term memory loss.
Delirium vs Major vs Mild NCD
| Feature | Delirium | Major NCD | Mild NCD |
|---|---|---|---|
| Onset | Acute (hrs–days) | Insidious (mo–yr) | Insidious |
| Course | Fluctuating | Progressive | Progressive |
| Attention | Impaired | Preserved early | Preserved |
| Awareness/consciousness | Altered | Clear | Clear |
| Independence (IADLs) | Variable | Lost | Preserved |
| Reversible | Often | Usually not | Usually not |
Vignette: An 82-year-old woman is post-op day 2 from hip repair. Overnight she is agitated, pulls at her IV, reports "bugs on the wall," and cannot recite the months backward; by morning she is calm and lucid. Exam: inattention, low-grade fever, suprapubic tenderness.
Diagnosis: Delirium (acute, fluctuating, inattentive) — likely a UTI ± post-op opioids/anticholinergics.
Next best step: Identify & treat the cause first — UA/culture, CBC, electrolytes/glucose, review the med list, check oxygenation. Non-pharmacologic measures are first-line (reorient, restore sleep-wake cycle, glasses/hearing aids, early mobilization, family at bedside).
If dangerously agitated: low-dose haloperidol. Avoid benzodiazepines (they worsen delirium) except in alcohol/sedative withdrawal, where benzos are first-line. Avoid physical restraints and anticholinergics.
Major NCD Subtypes & Mimics
| Subtype | Classic buzzwords | First-line drugs |
|---|---|---|
| Alzheimer | Insidious short-term memory loss; amyloid plaques + tau tangles | ChEI (donepezil) ± memantine |
| Vascular | Stepwise decline, focal deficits, vascular risk factors | Control vascular risk factors |
| Lewy body | Fluctuating cognition, visual hallucinations, parkinsonism, REM sleep behavior disorder | Rivastigmine; avoid typical antipsychotics |
| Frontotemporal | Young onset; personality/behavior change, disinhibition | Supportive (SSRI for behaviors) |
"I WATCH DEATH" — the classic differential for delirium etiologies:
- I — Infection (UTI, pneumonia, sepsis)
- W — Withdrawal (alcohol, benzodiazepines)
- A — Acute metabolic (electrolytes, hepatic/renal failure)
- T — Trauma (head injury, burns, post-op)
- C — CNS pathology (stroke, seizure, tumor)
- H — Hypoxia (anemia, cardiac/pulmonary failure)
- D — Deficiencies (B12, folate, thiamine)
- E — Endocrinopathies (thyroid, glucose, cortisol)
- A — Acute vascular (shock, hypertensive encephalopathy)
- T — Toxins/drugs (anticholinergics, opioids, sedatives)
- H — Heavy metals (lead, mercury)
Board tip: in the elderly, screen the top three culprits first — infection (UTI), medications, and metabolic derangements.
- Delirium — the whole game is the cause: work it up and fix it; layer non-pharmacologic care (reorientation, sleep hygiene, early mobilization, sensory aids, hydration).
- Agitated/dangerous delirium: low-dose haloperidol (or an atypical). Benzodiazepines only for alcohol/benzo withdrawal — delirium tremens (48–96 h after last drink) → lorazepam/chlordiazepoxide.
- Alzheimer/major NCD: cholinesterase inhibitors (donepezil, rivastigmine, galantamine) for mild–moderate; memantine (NMDA antagonist) for moderate–severe; the two can be combined.
- BPSD (agitation/psychosis in dementia): non-pharmacologic first; antipsychotics are last-resort — BLACK BOX: increased mortality in elderly with dementia.
- Depression + dementia: treat depression (SSRI) — reversible pseudodementia can improve.
- Lewy body: rivastigmine; if an antipsychotic is unavoidable use low-dose quetiapine/pimavanserin — never a typical agent (neuroleptic sensitivity).
Vignette: A 74-year-old man has 1 year of cognitive decline with day-to-day fluctuations, recurrent well-formed visual hallucinations (he sees children in the house), and rigidity with a shuffling gait. His wife reports he acts out his dreams. Given haloperidol in another ER, he became severely rigid and febrile.
Diagnosis: Dementia with Lewy bodies — fluctuating cognition + visual hallucinations + parkinsonism + REM sleep behavior disorder, with severe neuroleptic sensitivity. Dementia arising within ~1 year of parkinsonism → DLB (vs Parkinson disease dementia, where motor signs precede cognition by years).
Next best step: Stop the typical antipsychotic, then start a cholinesterase inhibitor (rivastigmine) for cognition and hallucinations. If an antipsychotic is truly required, use low-dose quetiapine or pimavanserin.
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