Electroencephalogram

This discusses EEG in the context of intensive care, predominantly in neuroprognostication.

Electrical tracing of cerebral activity that consists of both:

Background Patterns

Background activity is the most important prognostic feature, with progressive loss of background activity associated with increasingly poor prognosis. Key patterns include:

Earlier achievement of a good EEG background is associated with better prognosis.

  • Continuous background activity
    Good prognostic sign.
  • Discontinuous background activity
    Alternating continuous activity with suppression 10-40% of the time.
  • Burst suppression
    Long periods of electrographic silence with short bursts of activity.
    • Specific of very poor prognosis if exclusion of other causes:
      • Sedatives
      • Analgesics
      • Status epilepticus
      • Encephalopathy
      • Anoxic brain injury
      • Hypothermia
    • Epileptiform or identical bursts are associated with poor prognosis
  • Suppression
    Electrical silence >99% of the time. Due to:
    • Profound brain injury
    • Severe hypothermia
    • Deep anaesthesia
    • Acute hypoperfusion

Activity

Findings include:

  • Periodic discharge
    Repeating waveform at a set interval. Divided into:
    • Generalised Periodic Discharges on suppressed background
      Poor prognosis, and consistent with status myoclonus if clinical myoclonus present.
    • Periodic discharges on a continuous background
      Non-specific. May respond to antiepileptics.
  • Sporadic epileptiform discharges
    Repeating waveform at no regular interval. Generally poor prognosis.
  • Seizure
    Highly specific for poor outcome after cardiac arrest.
  • Status epilepticus
    Poor prognostic sign.

Other Findings

Diseases with specific findings include:

  • Hepatic encephalopathy
    Paroxysmal triphasic waves.
  • Herpes encephalitis
    Periodic sharp spikes.
  • Hypoxic encephalopathy
    • Theta activity
    • Diffuse slowing
    • Burst suppression
    • Alpha coma

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.