EEG ICU and Continuous EEG Monitoring 1 — Questions and Answers
Question 1: Continuous EEG (cEEG) monitoring in the ICU is most commonly indicated to detect:
- Nonconvulsive seizures and nonconvulsive status epilepticus (Correct answer)
- Sleep spindle frequency
- Cortical spreading depression only
- Brainstem reflexes
Correct answer: Nonconvulsive seizures and nonconvulsive status epilepticus
cEEG is the primary tool for identifying nonconvulsive seizures (NCS) and nonconvulsive status epilepticus (NCSE) in comatose or critically ill patients who cannot show motor signs.
Question 2: The American Clinical Neurophysiology Society (ACNS) standardized critical care EEG terminology defines a periodic discharge as a waveform recurring at a rate of at least:
- ≥1 Hz for ≥6 cycles (Correct answer)
- ≥3 Hz for ≥3 cycles
- ≥0.5 Hz for ≥10 cycles
- ≥2 Hz for ≥4 cycles
Correct answer: ≥1 Hz for ≥6 cycles
ACNS 2021 criteria define periodic discharges as recurring ≥1 Hz with ≥6 consecutive cycles showing a consistent morphology.
Question 3: Lateralized periodic discharges (LPDs), formerly called PLEDs, are most often associated with:
- Acute hemispheric structural lesions such as stroke or herpes encephalitis (Correct answer)
- Metabolic encephalopathy
- Brainstem infarction
- Corpus callosum injury
Correct answer: Acute hemispheric structural lesions such as stroke or herpes encephalitis
LPDs typically reflect acute or subacute focal cortical injury and are a common finding in herpes simplex encephalitis and hemispheric stroke.
Question 4: Burst suppression on EEG in a critically ill patient is characterized by:
- Alternating bursts of high-amplitude mixed activity and periods of near-flat EEG (Correct answer)
- Continuous high-amplitude delta slowing
- Repetitive spike-wave complexes at 3 Hz
- Beta-predominant activity with rare slow waves
Correct answer: Alternating bursts of high-amplitude mixed activity and periods of near-flat EEG
Burst suppression consists of bursts of mixed-frequency, often high-amplitude activity alternating with periods of electrocerebral suppression (<10 µV), indicating severe cerebral dysfunction.
Question 5: In continuous EEG monitoring, a quantitative EEG (qEEG) compressed spectral array (CSA) is used primarily to:
- Summarize hours of raw EEG into a compressed visual trend to detect seizures or ischemia (Correct answer)
- Replace raw EEG review entirely
- Measure exact spike counts per minute
- Generate automatic sleep stage scores
Correct answer: Summarize hours of raw EEG into a compressed visual trend to detect seizures or ischemia
CSA and other qEEG displays compress long EEG recordings into time-frequency trends, allowing technologists and clinicians to rapidly identify seizure activity or ischemic changes over hours.
Question 6: Which ICU patient population has the highest risk of nonconvulsive seizures, justifying prompt cEEG monitoring?
- Patients with acute convulsive status epilepticus treated with benzodiazepines (Correct answer)
- Patients with uncomplicated metabolic encephalopathy
- Patients with stable chronic epilepsy
- Postoperative patients after elective spine surgery
Correct answer: Patients with acute convulsive status epilepticus treated with benzodiazepines
After convulsive status epilepticus is terminated with benzodiazepines, up to 48% of patients continue to have nonconvulsive seizures detectable only by EEG.
EEG ICU and Continuous EEG Monitoring 1
Continuous EEG (cEEG) monitoring in the ICU is most commonly indicated to detect: