Can seizures and delirium occur simultaneously, and how can they be differentiated?

Can Seizures and Delirium Occur Simultaneously?

Yes, seizures and delirium can absolutely occur at the same time, and this co-occurrence is surprisingly common—approximately 48% of critically ill patients with seizures develop peri-ictal delirium, and 12-15% of older adults with delirium have epileptic activity on EEG. 1, 2, 3

Understanding the Co-occurrence

Frequency of Simultaneous Presentation

• Epileptic activity is present in 12-15% of older patients with delirium, including both interictal epileptiform discharges and non-convulsive status epilepticus (NCSE) 2, 3
• Nearly half (48%) of ICU patients experiencing seizures develop peri-ictal delirium within 24 hours of their seizures 1
• After cardiac surgery, 9% of patients show electrographic seizures, with a strong association between these seizures and delirium development 4

Why They Co-occur

• Both conditions share common precipitating factors including infection, toxic-metabolic disorders, electrolyte disturbances, drugs, hypoxia, and organ failure 5
• Dehydration and anticholinergic drug use are specifically associated with epileptic activity in delirious patients 3
• Epileptic activity may alter brain functioning and neuronal metabolism, potentially contributing to delirium pathophysiology 2

Key Differentiating Features

Temporal Characteristics

Delirium:

• Develops over hours to days with a fluctuating course that varies within minutes to hours 5
• Symptoms wax and wane throughout the day with possible lucid intervals 5
• Acute onset but sustained duration once established 5

Seizures:

• Acute interruption of brain function occurring suddenly 6
• Discrete episodes with clear beginning and end (though NCSE can be prolonged) 5, 6
• Transient occurrence due to abnormal excessive or synchronous neuronal activity 5

Core Clinical Features

Delirium (Cardinal Features):

• Inattention (inability to focus or sustain attention) 5
• Acute change in mental status or behavior 5
• Fluctuations in arousal or level of consciousness 5
• Disorganized thinking (disorientation, memory impairment, altered language) 5

Seizures:

• Convulsive activity (in generalized tonic-clonic seizures) 5, 6
• Focal motor or sensory symptoms (in focal seizures) 5
• Postictal confusion following the event 5
• Stereotyped, repetitive behaviors during the event 5

Level of Consciousness

Delirium:

• Impaired level of consciousness but patient remains arousable 5
• Reduced awareness of surroundings with difficulty focusing 5
• Does not occur in severely reduced arousal states like coma 5

Seizures:

• May have complete loss of awareness during the event 5
• Altered consciousness that is typically more profound during the ictal period 6
• Postictal state may resemble delirium temporarily 5

Critical Diagnostic Approach

Essential Assessment Steps

1. Obtain Collateral History:

• Interview a knowledgeable informant to establish baseline cognitive function and determine the time course, nature, and trajectory of changes 5
• Seek historical and semiological information from both patients and witnesses, including smartphone videos of episodes 7

2. Use Validated Screening Tools:

• Apply the Confusion Assessment Method (CAM) or its variants (CAM-ICU, B-CAM) for delirium detection 5
• Perform repeated assessments because cognitive status varies substantially within a day due to fluctuations in arousal, attention, and psychomotor state 5
• Consider the Intensive Care Delirium Screening Checklist (ICDSC) with a score ≥4 indicating delirium 1

3. Electroencephalography (EEG):

• EEG is essential for differentiating delirium from epileptic states, particularly non-convulsive status epilepticus 6
• Continuous EEG monitoring should be performed for at least 24 hours in older patients with delirium to detect epileptic activity 2
• Video-EEG of all typical seizure-like episodes should be obtained where feasible 7
• 84% of EEGs in delirious patients show abnormalities, with 15% demonstrating epileptic activity 3

Common Pitfalls to Avoid

Hypoactive Delirium Mimicking Postictal State:

• Hypoactive delirium presents with cognitive and motor slowing and a sedated appearance, which can be mistaken for a postictal state 5
• This subtype is more common in older individuals and carries greater risk of morbidity and mortality 5
• Look for the fluctuating course and inattention that characterize delirium rather than the progressive improvement typical of postictal states 5

Non-Convulsive Status Epilepticus (NCSE) Mimicking Delirium:

• NCSE can present with confusion and altered behavior without convulsive activity, making it clinically indistinguishable from delirium 6
• The absence of convulsive clinical activity is significant and requires EEG for diagnosis 6
• NCSE was found in 3% of delirious patients in one study, representing a treatable cause 2, 3

Assuming Mutual Exclusivity:

• Do not assume that diagnosing one condition excludes the other—they frequently coexist 1, 2, 4
• No clinical or biological marker reliably distinguishes delirious patients with or without epileptic activity 2

Management Implications

When Both Are Present

Parallel Treatment Approach:

• Obtain appropriate labs and studies to establish and treat the underlying causes of both conditions simultaneously 5
• Initiate measures to prevent delirium complications while managing seizures 5
• Manage delirium symptoms using non-pharmacological strategies first, and pharmacological strategies only in severe cases 5

Medication Considerations:

• Do not prescribe benzodiazepines or antiseizure medications for functional seizures or delirium alone without co-occurring epilepsy or another indication 7
• Be cautious with antipsychotics in hyperactive delirium, as they may worsen akathisia and behavioral activation 8
• Avoid anticholinergic drugs, which are associated with epileptic activity in delirious patients 3

Prognostic Considerations

Surprisingly, peri-ictal delirium in ICU patients with seizures is associated with:

• Lower illness severity scores (SAPS II) 1
• Shorter duration of mechanical ventilation 1
• Decreased odds of in-hospital death (OR = 0.41,95% CI 0.20-0.84) 1

However, epileptic activity in delirium shows:

• A trend toward longer hospital stays 3
• Higher institutionalization rates 3

When delirium is superimposed on pre-existing dementia:

• Accelerated cognitive and functional decline 5
• Increased length of hospital stay and higher rates of rehospitalization 5
• Greater mortality risk if delirium is missed (twice as high) 5

Clinical Bottom Line

Treat delirium as a medical emergency requiring immediate evaluation for underlying causes, including epileptic activity. 5 Obtain EEG in older patients with delirium, especially when the clinical picture is atypical or when delirium persists despite treatment of apparent precipitants. 2, 3, 6 The key distinguishing features are the fluctuating course and prominent inattention in delirium versus the stereotyped, episodic nature of seizures—but remember that 48% of seizure patients develop delirium, making concurrent evaluation essential. 1, 5