EEG ICU and Continuous EEG Monitoring 5 — Questions and Answers
Question 1: In a mechanically ventilated ICU patient, which artifact most commonly mimics rhythmic ictal activity on cEEG and must be systematically excluded?
- ECG artifact
- Ventilator artifact (Correct answer)
- Sweat artifact
- Pulse artifact
Correct answer: Ventilator artifact
Ventilator artifact produces rhythmic movement-related potentials synchronous with breathing cycles that can closely resemble rhythmic epileptiform activity, especially in frontal and central channels.
Question 2: Which of the following best defines the 'treatment threshold' concept for periodic discharges on the ictal-interictal continuum?
- Any periodic discharge warrants immediate IV benzodiazepines
- Treatment decisions depend on clinical context, imaging, and metabolic variables rather than EEG alone (Correct answer)
- Periodic discharges >1.5 Hz always require antiseizure medication
- Only generalized discharges require treatment consideration
Correct answer: Treatment decisions depend on clinical context, imaging, and metabolic variables rather than EEG alone
The ictal-interictal continuum requires clinical integration — treatment thresholds depend on the overall clinical picture, not solely on discharge frequency or morphology.
Question 3: What does a 'stimulus-induced rhythmic, periodic, or ictal discharges' (SIRPIDs) pattern indicate in a comatose ICU patient?
- Cortical spreading depression
- Preserved cortical reactivity with potential for seizure provocation (Correct answer)
- Brain death confirmation
- Metabolic encephalopathy pattern
Correct answer: Preserved cortical reactivity with potential for seizure provocation
SIRPIDs indicate that the cortex retains reactivity to external stimuli but responds with potentially epileptiform activity, suggesting an irritable cortex susceptible to seizure induction.
Question 4: In the setting of acute liver failure, which EEG pattern is characteristic and reflects hepatic encephalopathy grade III-IV?
- Frontal dominant triphasic waves with anterior-to-posterior lag (Correct answer)
- Generalized high-amplitude rhythmic theta activity
- Occipital dominant spike-wave complexes at 3 Hz
- Bilateral independent periodic lateralized discharges
Correct answer: Frontal dominant triphasic waves with anterior-to-posterior lag
Triphasic waves with a characteristic anterior-to-posterior phase lag are the classic EEG signature of moderate-to-severe hepatic encephalopathy, reflecting diffuse metabolic cortical dysfunction.
Question 5: During cEEG monitoring in a TBI patient, what does the appearance of 'breach rhythm' indicate?
- Subcortical seizure activity
- Skull defect causing amplitude enhancement and frequency changes (Correct answer)
- Pharmacologically induced EEG change
- Cortical spreading depolarization
Correct answer: Skull defect causing amplitude enhancement and frequency changes
Breach rhythm occurs over skull defects (craniectomy or fracture) where the missing bone allows higher amplitude and sharper-appearing waveforms due to reduced electrical filtering.
Question 6: Which cEEG finding in a post-cardiac arrest patient at 72 hours is most predictive of poor neurological outcome, even when therapeutic hypothermia has been applied?
- Persistent burst suppression with isoelectric interburst intervals (Correct answer)
- Intermittent generalized slowing with preserved reactivity
- Diffuse theta slowing with occasional vertex waves
- Low-voltage mixed frequency activity
Correct answer: Persistent burst suppression with isoelectric interburst intervals
Persistent burst suppression with flat (isoelectric) interburst intervals at 72 hours post-arrest is one of the strongest EEG predictors of poor neurological prognosis, even after therapeutic hypothermia.
Question 7: When a cEEG technologist notes an abrupt change from background suppression to high-amplitude rhythmic activity during routine care in an ICU patient, what is the FIRST appropriate step?
- Immediately administer IV lorazepam
- Notify the interpreting neurologist and document the clinical state at onset (Correct answer)
- Increase the high-frequency filter to remove artifact
- Discontinue cEEG and obtain an urgent CT head
Correct answer: Notify the interpreting neurologist and document the clinical state at onset
The technologist's immediate responsibility is to alert the interpreting neurologist and document concurrent clinical findings; treatment decisions are made by the physician after EEG review.
EEG ICU and Continuous EEG Monitoring 5
In a mechanically ventilated ICU patient, which artifact most commonly mimics rhythmic ictal activity on cEEG and must be systematically excluded?