How to diagnose delirium?

Diagnosing Delirium

Delirium is diagnosed through a structured clinical assessment focusing on acute onset, fluctuating course, inattention, altered level of consciousness, and disorganized thinking, using validated tools like the Confusion Assessment Method (CAM) while identifying underlying medical causes. 1, 2

Core Diagnostic Features

Delirium is characterized by:

• Acute onset and fluctuating course: Develops over hours to days, with symptoms that fluctuate within minutes to hours 1
• Inattention: Reduced ability to focus, sustain, or shift attention 1, 2
• Altered level of consciousness: Changes in arousal (hyperactive, hypoactive, or mixed) 1
• Disorganized thinking: Disorientation, memory impairment, altered language 1

Diagnostic Approach

Step 1: Use Validated Assessment Tools

• Confusion Assessment Method (CAM) is the most widely used diagnostic instrument with proven psychometric properties 1, 2
• CAM-ICU for intensive care settings 2
• Richmond Agitation Sedation Scale can help identify level of arousal 2

Step 2: Establish Baseline Cognitive Function

• Interview a knowledgeable informant about:
  • Previous baseline cognitive function
  • Timeline of changes
  • Nature and trajectory of symptoms 1
• Consider using the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) when indicated 1

Step 3: Identify Clinical Features

Look for:

1. Cognitive disturbances:

   • Disorientation to time, place, or person
   • Impaired immediate recall and recent memory
   • Visuospatial dysfunction
   • Language disturbance 1

2. Perceptual disturbances:

   • Hallucinations (usually visual or tactile)
   • Illusions
   • Misinterpretations
   • Transient delusions 1

3. Psychomotor changes:

   • Hyperactive: increased activity, agitation, restlessness
   • Hypoactive: reduced activity, lethargy, decreased speech (often missed)
   • Mixed: fluctuating features of both 1

4. Sleep-wake cycle disturbance:

   • Insomnia
   • Nightmares
   • Reversal of sleep-wake cycle
   • Nocturnal worsening of symptoms 1

5. Emotional disturbances:

   • Anxiety, fear, irritability
   • Emotional lability
   • Apathy, withdrawal 1

Step 4: Perform Repeated Assessments

• Cognitive status often varies substantially within a day
• Multiple assessments help capture fluctuations in arousal, attention, and psychomotor state 1

Differentiating Delirium from Other Conditions

Feature	Delirium	Dementia
Onset	Acute (hours to days)	Insidious (months to years)
Course	Fluctuating	Stable, gradually progressive
Attention	Severely impaired	Generally preserved until late stages
Consciousness	Altered	Clear until late stages
Reversibility	Often reversible with treatment	Generally irreversible
Hallucinations	Common	Less common (except in certain types)
Sleep-wake cycle	Disturbed	Usually preserved until late stages
[2]

Common Pitfalls to Avoid

• Missing hypoactive delirium: More common in older individuals and associated with greater morbidity and mortality 1, 2
• Failing to recognize delirium superimposed on dementia: Particularly challenging but critical as it represents a medical emergency 1, 2
• Overlooking subsyndromal or atypical delirium: Can be caused by sleep disturbances, alcohol intake, or medications in vulnerable individuals 1
• Inadequate collateral history: Essential for establishing baseline cognitive function 1
• Single assessments: May miss fluctuating symptoms 1

Identifying Underlying Causes

Once delirium is diagnosed, promptly investigate for underlying causes:

• Infections
• Toxic-metabolic disorders
• Electrolyte and hydration disturbances
• Medications
• Hypoxia
• Organ failure 1

Obtain appropriate laboratory tests and studies to establish and treat the cause(s) of delirium, as this is a medical emergency that if left untreated may be fatal or lead to irreversible cognitive and functional losses 1, 2.