What are the key differences in EEG findings and management between delirium and seizures?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: September 7, 2025 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

EEG Differences Between Delirium and Seizures

The key EEG difference between delirium and seizures is that delirium typically shows diffuse slowing with increased delta (<4 Hz) and theta (4-8 Hz) oscillations and decreased alpha (>8 Hz) activity, while seizures show paroxysmal epileptiform discharges that may evolve in frequency, amplitude, and spatial distribution. 1

Characteristic EEG Findings

Delirium EEG Patterns

  • Background activity: Diffuse slowing of background activity 1
  • Frequency changes:
    • Increased delta (<4 Hz) and theta (4-8 Hz) oscillations
    • Decreased alpha (>8 Hz) oscillations 1
  • Functional connectivity: Impaired and less integrated, especially following stressors 1
  • Spectral variability: Increased with often periodic discharges such as triphasic waves and polymorphic delta activity 1
  • Severity correlation: EEG changes correlate with cognitive performance and delirium severity 1
  • Diagnostic accuracy: Quantitative EEG can distinguish delirious from non-delirious patients with sensitivity of 100% and specificity of 99% 1

Seizure EEG Patterns

  • Epileptiform discharges: Sharp waves, spikes, or spike-and-wave complexes 1
  • Evolution: Changes in frequency, amplitude, or spatial distribution over time 1
  • Post-ictal state: Diffuse slowing after seizure activity resolves 1
  • Non-convulsive status epilepticus (NCSE): Continuous epileptiform activity without obvious clinical seizures 1

Diagnostic Challenges and Overlap

Distinguishing Features

  1. Pattern evolution: Seizure activity typically shows evolution in frequency and amplitude, while delirium shows more consistent slowing 1
  2. Response to treatment: Seizure patterns typically respond to anticonvulsants, while delirium EEG changes persist unless underlying cause is addressed 2
  3. Spatial distribution: Seizures may have focal onset before spreading, while delirium typically shows diffuse abnormalities from onset 1

Potential Overlap

  • NCSE presenting as delirium: Up to 28% of elderly patients with delirium show EEG patterns compatible with NCSE when continuous EEG monitoring is performed 3
  • Post-ictal state: Can be confused with delirium due to similar EEG findings of diffuse slowing 1
  • Altered consciousness: Both conditions can present with altered level of consciousness and similar EEG findings 1

Clinical Implications for Management

When to Suspect Seizures in Apparent Delirium

  • Fluctuating level of consciousness without clear metabolic cause 1
  • History of epilepsy or recent seizure activity 1
  • Lack of response to standard delirium management 4
  • Subtle motor manifestations (eye or facial twitching, automatisms) 1

EEG Monitoring Recommendations

  • Consider emergent EEG in patients suspected of being in non-convulsive status epilepticus or subtle convulsive status epilepticus 1
  • Continuous EEG monitoring is superior to routine 20-minute EEG for detecting patterns compatible with NCSE (28% vs 6% detection rate) 3
  • Regular reassessment with repeat EEG to assess treatment efficacy in cases where seizure activity is suspected 4

Treatment Implications

  • For seizure activity: Lorazepam 4 mg IV given slowly (2 mg/min) is the recommended initial treatment for status epilepticus in adults 2
  • For delirium without seizure activity: Focus on treating underlying causes and providing supportive care 4
  • When both are suspected: Treat for possible NCSE while investigating and addressing underlying causes of delirium 1, 4

High-Risk Populations

  • Elderly patients: Higher risk of both delirium and non-convulsive status epilepticus 5, 3
  • ICU patients: Delirium affects approximately 31% of ICU patients 6
  • Patients with cognitive impairment: More susceptible to both conditions 3
  • Patients with electrolyte abnormalities: Particularly hypernatremia, which is associated with NCSE in delirious patients 3

Prognostic Significance

  • Patients with delirium and patterns compatible with NCSE have significantly higher mortality rates and longer hospital stays 3
  • The degree of EEG changes correlates with the severity of encephalopathy and can be used to monitor therapy 7

Remember that while EEG is a valuable diagnostic tool, clinical correlation is essential, and treatment decisions should be based on both EEG findings and clinical presentation.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

4
Guideline

Management of Metabolic Encephalopathy and Delirium in ESRD Patients on Hemodialysis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

7
Research

Utility of EEG in delirium: past views and current practice.

International psychogeriatrics, 1991

Related Questions

Is imaging and EEG an appropriate next step for a patient with a history of recurrent stroke, diabetes, and chronic kidney disease presenting with delirium without fever and normal blood tests, including complete blood counts (CBC), electrolyte levels, and stable renal function?
What is better, the 4AT (Four Assessment Tool) or the CAM (Confusion Assessment Method) for assessing delirium?
What primarily forms complexes that precipitate in tissues due to self-antigens, B cells or autoantibodies?
Which cells, T cells or B cells, are primarily involved in modulating immune activity and may be implicated in the breakdown of self-tolerance leading to autoimmune reactions?
How can large class sizes be overcome as a barrier to implementing Problem-Based Learning (PBL) in medical education?
What are the recommended treatments for a persistent cough?
What is the difference between edema and anasarca in terms of treatment and management?
What is the recommended dosing of Levofloxacin (a fluoroquinolone antibiotic) for acute otitis media?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question