Acute confusion and delirium versus focal neurological disease

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Acute confusion is a presenting description; delirium is a clinical syndrome; neither specifies the cause. Delirium develops when vulnerability—age, frailty, dementia, sensory impairment or severe illness—interacts with insults such as infection, surgery, hypoxia, metabolic disturbance, medicine toxicity, pain or environmental disruption. Finding one plausible trigger should not end the search when physiology, history or focal signs point to another simultaneous process.

Attention is the core bedside domain. Ask the patient to state months backwards or use the attention component of a validated instrument while first ensuring hearing, language and arousal permit participation. Disorganised thought, perceptual disturbance and sleep–wake reversal support delirium, but orientation can remain correct. A single normal interaction does not exclude a syndrome that fluctuates; nursing and family observations across the day are diagnostically valuable.

Focal neurological disease often masquerades as global confusion. Receptive aphasia produces fluent but nonsensical speech and poor command-following; non-dominant parietal stroke can cause neglect and loss of insight; posterior-circulation stroke can produce reduced alertness or severe gait dysfunction; frontal lesions change behaviour. Examine gaze, fields, face, limbs, sensation, language, neglect and coordination rather than relying on orientation questions alone.

Delirium and dementia frequently coexist. Dementia generally develops over months or years and provides vulnerability, while a sudden decline from that baseline indicates superimposed delirium until assessed. Depression, psychosis and functional disorders enter the differential only after physiological and neurological causes have been considered. Capacity is decision-specific and time-specific; optimise communication and revisit decisions as attention improves.

Key points

Delirium is an acute, usually fluctuating disturbance of attention and awareness with additional cognitive change. Hyperactive, hypoactive and mixed forms occur; quiet withdrawal is commonly missed.
Obtain baseline cognition, function and communication from someone who knows the patient, then establish hours-to-days onset, fluctuation and recent precipitant rather than accepting 'confused' as a diagnosis.
Use the 4AT or the locally mandated validated tool when delirium is suspected, but treat it as a structured assessment rather than a laboratory test that replaces clinical judgement.
Check glucose, oxygenation, ventilation, temperature, blood pressure, medication exposure, pain, urinary retention, constipation, hydration and withdrawal early because several triggers often coexist.
Aphasia can look like confusion: test naming, repetition, comprehension and fluency. Neglect can look inattentive, visual-field loss can look disoriented and apraxia can look uncooperative.
Sudden confusion with unilateral weakness, gaze deviation, visual loss, aphasia, neglect or severe imbalance should enter the stroke pathway even when a delirium trigger is also present.
Non-convulsive seizure may cause fluctuating responsiveness, speech arrest, automatisms, eye deviation or unexplained failure to recover; urgent EEG advice is warranted when the clinical pattern fits.
Fever, headache, personality change, focal deficit or seizure can signal encephalitis or meningitis. Empirical treatment must not wait for lumbar puncture when the procedure is delayed or unsafe.
Medication reconciliation includes new prescriptions, dose changes, anticholinergic burden, opioids, benzodiazepines, corticosteroids, dopaminergic drugs, over-the-counter products, alcohol and illicit substances.
Management begins with treating causes and providing orientation, hydration, sensory aids, sleep support, mobilisation and family involvement; restraint or sedation can worsen outcomes and needs exceptional justification.
Document attention, arousal, focal examination, collateral baseline, capacity for the specific decision and the plan to reassess. Delirium does not equal permanent incapacity.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Acute physiological illness

Infection, hypoxia, hypercapnia, dehydration, pain, urinary retention, constipation and metabolic disturbance commonly precipitate delirium, often with several contributors acting simultaneously.

Medicines, toxins and withdrawal

Anticholinergic or sedating medicines, opioids, corticosteroids, dopaminergic treatment, alcohol and illicit substances can alter attention; recent initiation, accumulation or withdrawal is particularly informative.

Primary neurological disease

Stroke, seizure, encephalitis, meningitis, head injury and raised intracranial pressure may present as apparent confusion, especially when aphasia, neglect or reduced consciousness obscures focal signs.

Reduced cerebral reserve

Dementia, frailty, severe illness, sensory impairment and unfamiliar environments lower the threshold at which a relatively modest physiological insult disrupts cognition and awareness.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Vulnerability meets insult
Pre-existing loss of cerebral reserve reduces the brain's ability to maintain attention and arousal when inflammation, hypoperfusion, metabolic change or drug exposure disturbs homeostasis.
2
Network and transmitter dysfunction
Acute systemic or neurological stress disrupts distributed attention networks and alters cholinergic, dopaminergic and stress signalling, impairing integration of sensory information and organised thought.
3
Fluctuating cognitive failure
Changing physiology, sleep disruption and environmental demands cause variable arousal, inattention, disorganised thinking and perceptual disturbance across hours, producing hyperactive, hypoactive or mixed delirium.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Hypoactive deliriumRed flag

Reduced movement, slow responses, sleepiness, poor intake and withdrawal with impaired attention may be mistaken for depression, fatigue or 'pleasant confusion'. It carries substantial risk and requires the same cause search as agitation.

Hyperactive deliriumRed flag

Agitation, fear, hallucinations, sleep reversal and attempts to leave occur with fluctuating attention and disorganised thought. Pain, hypoxia, retention, withdrawal and an unfamiliar environment can all amplify behaviour.

Dominant-hemisphere stroke mimicryRed flag

Receptive or global aphasia can present as nonsensical answers, inability to follow instructions and apparent confusion. Sudden onset, paraphasia, naming or repetition impairment and lateralising signs support urgent stroke assessment.

Non-dominant parietal syndromeRed flag

Neglect, visuospatial disorientation, extinction, dressing difficulty and poor insight can appear as global cognitive disturbance. A lateralised attention deficit with abrupt onset is a focal cerebral syndrome.

Encephalitic syndromeRed flag

Subacute fever, headache, altered behaviour, memory disturbance, focal seizure or neurological deficit suggests brain inflammation. Normal initial imaging or absence of neck stiffness does not exclude encephalitis.

Non-convulsive status patternRed flag

Persistent or fluctuating impaired awareness after a seizure, unexplained speech arrest, subtle twitching, automatisms or gaze deviation can reflect continuing electrical seizure despite no generalised convulsion.

Chronic cognitive disorder

A reproducible history of gradual cognitive and functional decline over months supports dementia, but any acute step-down, inattention or fluctuation still requires assessment for superimposed delirium and focal disease.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
4AT with collateral baseline and serial reviewFirst step
Why
Identify altered alertness, impaired attention, acute change and fluctuation in a structured way.
Interpretation and limitations
A score suggesting delirium supports a clinical diagnosis but does not identify cause. Severe aphasia, reduced consciousness, hearing loss and language difference alter performance and should be documented rather than converted into false certainty.
02
Glucose, observations, ECG and bedside examination
Why
Detect immediate physiological threats, arrhythmia and focal neurological or meningeal signs.
Interpretation and limitations
Correct hypoglycaemia and hypoxia promptly. Fever absence does not exclude infection, and normal oxygen saturation does not exclude hypercapnia; blood gas testing is guided by respiratory context.
03
FBC, U&E, calcium, CRP, liver tests and selected cultures
Why
Investigate infection, dehydration, organ dysfunction and biochemical precipitants based on the clinical picture.
Interpretation and limitations
Small abnormalities are common in frail patients and need temporal and severity correlation. Culture only when a source is plausible and avoid treating asymptomatic bacteriuria as the automatic explanation.
04
Medication, alcohol and substance review
Why
Identify toxicity, interaction, anticholinergic burden, missed dependence treatment or withdrawal.
Interpretation and limitations
Verify dispensing, administration and dose changes with records and collateral sources. Drug screens cover limited compounds and can remain positive after clinical effects have resolved.
05
CT or MRI brain
Why
Evaluate trauma, focal deficit, seizure, headache, anticoagulation, reduced consciousness and unexplained persistent delirium where structural disease is plausible.
Interpretation and limitations
Imaging is not mandatory for every uncomplicated precipitant, but sudden focal or declining neurology requires urgent scanning. A normal CT cannot exclude early infarction, encephalitis or non-convulsive seizure.
06
EEG and cerebrospinal-fluid studies
Why
Investigate non-convulsive seizure, encephalitis, meningitis or inflammatory disease after specialist and safety assessment.
Interpretation and limitations
EEG is time-limited and sedation changes the trace. If CNS infection is suspected, obtain appropriate samples when safe but begin empirical antimicrobials or antiviral therapy without harmful delay.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Focal stroke with aphasia or neglect

Sudden language failure, gaze or field deviation, unilateral weakness, neglect or severe imbalance supports stroke; orientation questions alone can mistake focal cortical dysfunction for global confusion.

Non-convulsive seizure

Fluctuating responsiveness, speech arrest, automatisms, eye deviation or failure to recover after a convulsion should prompt electroencephalographic assessment rather than attribution to ordinary delirium.

Encephalitis or meningitis

Fever, headache, meningism, seizures, personality change or focal deficits support central infection or inflammation and require time-critical treatment alongside diagnostic sampling.

Dementia or psychiatric illness

Months-to-years decline suggests dementia and a coherent psychiatric syndrome may mimic confusion, but an abrupt fluctuating change from baseline indicates superimposed delirium until assessed.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Acute global confusionConfirm delirium and treat causesFirst stepHours-to-days cognitive change, impaired attention or fluctuating alertness without an immediately dominant focal syndrome.

1Perform ABCDE and glucose, obtain collateral baseline, use 4AT or the local validated assessment, and examine for focal neurology, meningism, trauma, pain, retention, constipation and dehydration.
2Investigate and treat plausible precipitants, rationalise medicines and withdrawal risk, and implement orientation, sensory aids, hydration, nutrition, sleep, mobilisation and familiar support.
3EscalationReview attention and arousal serially, escalate failure to improve or new focal signs, and communicate the syndrome, capacity implications and safety plan at every transition.

02Possible focal brain diseaseDo not let confusion obscure strokeAbrupt onset, language disturbance, neglect, gaze or field change, unilateral deficit, severe ataxia or a new unusual headache.

1Establish last known well, examine naming, repetition, comprehension, fields, gaze, face and all limbs and check glucose while activating the appropriate stroke or neuro-emergency team.
2Obtain urgent brain and vascular imaging selected by the receiving pathway; do not postpone because infection, dementia or medication toxicity also seems plausible.
3Provide swallow, observation and reperfusion-related care under specialist direction, then investigate concurrent delirium precipitants after time-critical decisions are protected.

03Dangerous agitationDe-escalate while correcting physiologyEscalationBehaviour creates immediate risk to the patient or others and verbal engagement is difficult because of delirium.

1Call sufficient trained help, reduce noise, use one calm communicator, address pain, hypoxia, hypoglycaemia, retention and withdrawal, and preserve dignity and least-restrictive care.
2EscalationUse non-pharmacological de-escalation first; if immediate risk persists, seek senior review and follow NICE and local policy for the lowest appropriate short-term medicine with ECG and contraindication consideration.
3Observe airway, vital signs, sedation and mobility after any intervention, stop the medicine as soon as possible and document indication, alternatives attempted, capacity and review time.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

May reduce severe distress or immediate behavioural risk; it does not treat delirium's underlying cause and is not routine first-line care.

Short-term haloperidol in exceptional delirium-related distress

If non-drug de-escalation fails and the person remains distressed or dangerous, use the lowest clinically appropriate dose for the shortest possible time, ordinarily no longer than one week, under senior and local policy.

Avoid or seek specialist advice in Parkinson's disease or Lewy-body dementia; assess QT prolongation, cardiovascular risk, electrolyte disturbance, extrapyramidal effects and interactions, particularly in frail older adults.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Aspiration, falls and pressure injury

Inattention, altered arousal and disorganised movement impair swallowing and safe mobility, increasing pneumonia, fractures, skin damage and the need for supervised supportive care.

Functional and cognitive decline

Immobility, sleep disruption and severe illness accelerate deconditioning and can leave prolonged cognitive impairment, particularly in frail people or those with pre-existing dementia.

Treatment-related harm

Unnecessary restraint, sedation or antipsychotic exposure can worsen confusion, aspiration, falls and cardiac or extrapyramidal risk, while diagnostic overshadowing delays treatment of the precipitating disease.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Repeat attention, alertness and focal neurological findings across shifts because fluctuation is characteristic and deterioration may reveal a new structural cause.
Trend hydration, intake, urine and bowel function, pain, sleep, mobility and oxygen requirement alongside laboratory values rather than focusing on behaviour alone.
Review every deliriogenic medicine daily and document stop, restart or dose decisions with the original indication and withdrawal risk.
After any sedating or antipsychotic intervention, observe airway, consciousness, ECG-relevant physiology, extrapyramidal effects, falls and aspiration risk.
Reassess decision-specific capacity after communication support and clinical improvement; a delirium label should not create an indefinite global incapacity entry.
At discharge or transfer, communicate baseline cognition, likely precipitants, unresolved tests, current cognitive state and a plan for persistent symptoms.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Orientation can be preserved

A patient may state date and place correctly yet be unable to sustain attention or follow a conversation. Normal orientation alone does not exclude delirium.

Aphasia changes test validity

Poor verbal responses in receptive aphasia can inflate cognitive-screen scores and look like inattention. Observe non-verbal command following and localising cortical signs while pursuing urgent imaging.

Delirium has multiple causes

Finding pneumonia does not rule out medication toxicity, retention or a subdural collection. Vulnerable patients often require several insults to be identified and corrected.

Hypoactivity is high risk

A quiet patient creates less disruption but may have severe physiological illness, dehydration and aspiration risk. Proactive screening prevents systematic under-recognition.

Capacity is not a score

Capacity requires understanding, retention, use or weighing and communication for one decision at one time. Neither a 4AT result nor a diagnosis automatically decides it.

Recovery can be prolonged

Attention and function may remain impaired after the precipitant improves, particularly with frailty or dementia. Persistent change still deserves review rather than automatic acceptance as a new baseline.

11Common pitfallsFrequent interpretation and management errors.

01
Calling an acutely withdrawn patient tired and missing hypoactive delirium.
02
Treating a positive urine dipstick as proof that bacteriuria caused every cognitive change.
03
Assuming inability to follow spoken commands is global confusion without testing language and hearing.
04
Giving sedative medication before correcting pain, hypoxia, glucose, retention or withdrawal.
05
Failing to activate a stroke pathway because the patient also has infection or known dementia.
06
Using physical restraint as routine fall prevention without least-restrictive review and monitoring.
07
Discharging after behavioural improvement without communicating unresolved cognitive and functional change.