EEG Non-Epileptiform Abnormalities 5 — Questions and Answers
Question 1: Which non-epileptiform EEG pattern is characterized by high-voltage, chaotic slow and sharp waves without organized background activity, classically seen in infantile spasms?
- Hypsarrhythmia (Correct answer)
- Burst suppression
- GRDA
- Triphasic waves
Correct answer: Hypsarrhythmia
Hypsarrhythmia is the interictal EEG hallmark of West syndrome (infantile spasms), featuring high-amplitude disorganized slow activity with multifocal spikes.
Question 2: Generalized rhythmic delta activity (GRDA) persisting despite stimulation is most suggestive of which condition compared to GRDA that attenuates with stimulation?
- GRDA that persists is more likely ictal; GRDA that attenuates is more likely non-ictal (Correct answer)
- GRDA that persists is more benign; GRDA that attenuates indicates seizure
- Both have identical clinical significance
- Persistence indicates artifact only
Correct answer: GRDA that persists is more likely ictal; GRDA that attenuates is more likely non-ictal
GRDA that does not attenuate with stimulation (non-reactive) raises concern for ictal or peri-ictal activity, while stimulus-induced attenuation suggests non-epileptiform encephalopathy.
Question 3: Which medication commonly produces diffuse beta activity as a non-epileptiform EEG abnormality?
- Haloperidol
- Benzodiazepines (Correct answer)
- Levetiracetam
- Phenytoin
Correct answer: Benzodiazepines
Benzodiazepines and barbiturates classically increase diffuse beta activity (>13 Hz), which is a drug effect rather than a pathological finding.
Question 4: An EEG showing continuous generalized polymorphic delta slowing with no clear faster frequencies in a patient with altered consciousness most likely indicates what?
- Stage 3 NREM sleep
- Severe diffuse cortical dysfunction (Correct answer)
- Normal drowsiness pattern
- REM sleep
Correct answer: Severe diffuse cortical dysfunction
Continuous generalized polymorphic delta without faster activity in a wakeful patient indicates severe diffuse encephalopathy affecting cortical function.
Question 5: TIRDA (Temporal Intermittent Rhythmic Delta Activity) is considered a non-epileptiform abnormality but is clinically significant because it is associated with which condition?
- Normal aging
- Temporal lobe epilepsy (Correct answer)
- Frontal lobe tumors
- Metabolic alkalosis
Correct answer: Temporal lobe epilepsy
TIRDA, while not epileptiform itself, is strongly associated with temporal lobe epilepsy and should prompt clinical correlation for seizure disorder.
Question 6: Which EEG feature differentiates true electrocerebral inactivity from a technical artifact producing an isoelectric-appearing record?
- Performing a photic stimulation test
- Increasing interelectrode distances, confirming low impedances, and testing reactivity with painful stimuli (Correct answer)
- Switching to referential montage only
- Recording for exactly 20 minutes
Correct answer: Increasing interelectrode distances, confirming low impedances, and testing reactivity with painful stimuli
Confirming ECI requires technical verification including electrode impedances <10 kΩ, interelectrode distance ≥10 cm, high sensitivity settings, and absence of reactivity to stimulation.
Question 7: A patient with uremic encephalopathy undergoes EEG. Which pattern would be an expected non-epileptiform abnormality in this setting?
- Prominent alpha activity at 10–12 Hz
- Diffuse theta-delta slowing with possible triphasic waves (Correct answer)
- Persistent beta spindle activity
- Well-organized posterior dominant rhythm
Correct answer: Diffuse theta-delta slowing with possible triphasic waves
Uremic encephalopathy typically produces diffuse background slowing into the theta and delta ranges, sometimes with triphasic morphology similar to hepatic encephalopathy.
EEG Non-Epileptiform Abnormalities 5
Which non-epileptiform EEG pattern is characterized by high-voltage, chaotic slow and sharp waves without organized background activity, classically seen in infantile spasms?