CNIM Electroencephalography (EEG) in the Operating Room 2 — Questions and Answers
Question 1: Burst suppression on intraoperative EEG is BEST described as:
- Continuous high-amplitude delta activity without interruption
- Alternating periods of complete electrocerebral silence and bursts of mixed-frequency activity (Correct answer)
- Persistent 3 Hz spike-and-wave discharges throughout the recording
- Generalized increase in beta activity with superimposed muscle artifact
Correct answer: Alternating periods of complete electrocerebral silence and bursts of mixed-frequency activity
Burst suppression consists of alternating episodes of electrical silence (suppression) and bursts of activity, reflecting profound but reversible cerebral metabolic depression.
Question 2: During carotid endarterectomy, which EEG change is MOST indicative of cerebral ischemia following carotid cross-clamping?
- Bilateral increase in alpha power
- Unilateral amplitude reduction and frequency slowing ipsilateral to the clamp (Correct answer)
- Appearance of bilateral sleep spindles
- Generalized beta activity increase across all channels
Correct answer: Unilateral amplitude reduction and frequency slowing ipsilateral to the clamp
Ipsilateral amplitude decrease and new delta slowing after carotid clamping are the classic EEG signs of inadequate hemispheric perfusion, prompting shunt placement.
Question 3: Which anesthetic agent is most associated with producing epileptiform EEG discharges during induction?
- Propofol
- Isoflurane
- Sevoflurane
- Etomidate (Correct answer)
Correct answer: Etomidate
Etomidate can elicit myoclonic movements and cortical epileptiform discharges on EEG during induction, requiring careful distinction from pathological seizure activity.
Question 4: As anesthetic depth progressively increases, the general EEG pattern shifts:
- From delta slowing toward faster beta activity
- From faster frequencies (beta/alpha) toward slower frequencies (theta then delta) (Correct answer)
- Remains stable at alpha frequencies regardless of depth
- Immediately transitions to isoelectric silence without intermediate stages
Correct answer: From faster frequencies (beta/alpha) toward slower frequencies (theta then delta)
Increasing anesthetic depth progressively slows the EEG from fast beta activity through theta to delta dominance, and ultimately to burst suppression at very deep levels.
Question 5: At typical surgical maintenance doses of propofol (TIVA), the characteristic EEG pattern is:
- Continuous high-amplitude delta with no faster frequencies
- Alpha oscillations and spindle-like beta activity (the 'propofol alpha') (Correct answer)
- Persistent burst suppression throughout the case
- Completely isoelectric (flat) tracing
Correct answer: Alpha oscillations and spindle-like beta activity (the 'propofol alpha')
Propofol at maintenance doses produces a distinctive anteriorly dominant alpha/beta oscillatory pattern, sometimes called the 'propofol alpha,' reflecting its unique GABAergic mechanism.
Question 6: Focal EEG slowing isolated to the left temporal region during cerebrovascular surgery MOST likely indicates:
- A normal variant of the aging brain
- Artifact from a poorly placed electrode
- Regional cerebral dysfunction, such as ischemia or structural compromise (Correct answer)
- The expected effect of neuromuscular blocking agents
Correct answer: Regional cerebral dysfunction, such as ischemia or structural compromise
Focal delta slowing confined to one brain region during vascular surgery suggests localized cerebral compromise, raising concern for ischemia in that vascular territory.
Question 7: Electrocerebral silence (ECS) discovered during intraoperative EEG monitoring requires the neurophysiologist to FIRST:
- Immediately declare brain death and notify the surgeon
- Verify technical factors such as electrode connections, sensitivity settings, and amplifier function before clinical interpretation (Correct answer)
- Increase the high-frequency filter to reveal hidden activity
- Administer a reversal agent to the anesthesiologist
Correct answer: Verify technical factors such as electrode connections, sensitivity settings, and amplifier function before clinical interpretation
Before attributing a flat EEG to neurological catastrophe, all technical causes (disconnected electrodes, sensitivity errors, amplifier faults) must be systematically excluded.
CNIM Electroencephalography (EEG) in the Operating Room 2
Burst suppression on intraoperative EEG is BEST described as: