EEG ICU and Continuous EEG Monitoring 4 — Questions and Answers
Question 1: Which EEG pattern in a comatose patient is most associated with nonconvulsive status epilepticus (NCSE)?
- Burst suppression with flat interburst intervals
- Rhythmic or periodic discharges evolving in frequency or morphology (Correct answer)
- Diffuse slowing with theta predominance
- Alpha coma pattern with unreactive background
Correct answer: Rhythmic or periodic discharges evolving in frequency or morphology
Rhythmic or periodic discharges that evolve in frequency, morphology, or spatial distribution are the hallmark EEG feature of NCSE in critically ill patients.
Question 2: In continuous EEG monitoring, what is the recommended minimum duration of recording to detect the majority of seizures in high-risk ICU patients?
- 2 hours
- 6 hours
- 24 hours (Correct answer)
- 48 hours
Correct answer: 24 hours
Studies show that 24 hours of continuous EEG monitoring captures approximately 80–90% of seizures in high-risk ICU patients.
Question 3: A patient post-cardiac arrest shows an EEG with suppression-burst ratio >50% and identical burst morphology across channels. What does this suggest?
- Favorable prognosis for neurological recovery
- Therapeutic hypothermia artifact
- Severe diffuse cortical injury with poor prognosis (Correct answer)
- Focal cortical dysplasia
Correct answer: Severe diffuse cortical injury with poor prognosis
High suppression-burst ratios with stereotyped bursts in post-cardiac arrest patients indicate severe anoxic brain injury and are associated with poor neurological outcomes.
Question 4: Which quantitative EEG (qEEG) trend is most useful for detecting secondary cerebral ischemia in subarachnoid hemorrhage patients?
- Relative alpha variability (RAV) (Correct answer)
- Burst suppression ratio
- Epileptiform discharge index
- Interhemispheric coherence
Correct answer: Relative alpha variability (RAV)
Relative alpha variability decreases prior to and during delayed cerebral ischemia in SAH patients, making it the most validated qEEG marker for vasospasm detection.
Question 5: When interpreting cEEG in a patient receiving midazolam infusion, which pattern is expected and should not be mistaken for pathology?
- Frontal intermittent rhythmic delta activity (FIRDA)
- Diffuse beta activity with spindle-like waveforms (Correct answer)
- Triphasic wave morphology
- Vertex sharp waves
Correct answer: Diffuse beta activity with spindle-like waveforms
Benzodiazepines and other sedatives typically produce diffuse beta frequency enhancement that can resemble sleep spindles and is a normal pharmacological effect.
Question 6: A continuous EEG shows lateralized periodic discharges (LPDs) at 2 Hz in a patient with herpes simplex encephalitis. What is the significance of LPDs in this context?
- They confirm the diagnosis of HSV encephalitis
- They represent a benign artifact from electrode impedance mismatch
- They indicate ictal or interictal activity and require antiseizure consideration (Correct answer)
- They are pathognomonic for focal cortical dysplasia
Correct answer: They indicate ictal or interictal activity and require antiseizure consideration
LPDs in HSV encephalitis represent a continuum between interictal and ictal activity (the 'ictal-interictal continuum') and typically warrant antiseizure medication evaluation.
Question 7: Which electrode placement is most critical to include when performing cEEG specifically to detect subcortical or deep seizure activity in ICU patients?
- Nasopharyngeal or sphenoidal electrodes
- Temporal chain electrodes (T3, T4, T5, T6) (Correct answer)
- Midline electrodes (Fz, Cz, Pz)
- Ear reference electrodes (A1, A2)
Correct answer: Temporal chain electrodes (T3, T4, T5, T6)
Temporal chain electrodes are essential for capturing mesial temporal lobe seizures, which are among the most common seizure types missed with reduced electrode arrays in ICU cEEG.
EEG ICU and Continuous EEG Monitoring 4
Which EEG pattern in a comatose patient is most associated with nonconvulsive status epilepticus (NCSE)?