EEG Abnormal Epileptiform Patterns 4 — Questions and Answers
Question 1: Which EEG pattern is characterized by bilateral synchronous 3-Hz spike-and-wave discharges that are typically enhanced by hyperventilation?
- Childhood absence epilepsy (Correct answer)
- Juvenile myoclonic epilepsy
- Lennox-Gastaut syndrome
- Dravet syndrome
Correct answer: Childhood absence epilepsy
Childhood absence epilepsy classically produces bilateral synchronous 3-Hz spike-and-wave discharges that are strongly activated by hyperventilation.
Question 2: A patient's EEG shows slow (1–2.5 Hz) spike-and-wave complexes during sleep alongside atonic and tonic seizures. Which syndrome does this pattern most suggest?
- West syndrome
- Lennox-Gastaut syndrome (Correct answer)
- Dravet syndrome
- Angelman syndrome
Correct answer: Lennox-Gastaut syndrome
Lennox-Gastaut syndrome is defined by slow (1–2.5 Hz) spike-and-wave, multiple seizure types including atonic and tonic, and intellectual disability.
Question 3: Hypsarrhythmia on EEG is the interictal hallmark of which epilepsy syndrome?
- Lennox-Gastaut syndrome
- Ohtahara syndrome
- West syndrome (Correct answer)
- Landau-Kleffner syndrome
Correct answer: West syndrome
Hypsarrhythmia — chaotic high-amplitude activity with multifocal spikes — is the characteristic interictal EEG pattern of West syndrome (infantile spasms).
Question 4: On EEG, a burst-suppression pattern in a neonate without hypothermia treatment most likely indicates which condition?
- Benign neonatal sleep myoclonus
- Ohtahara syndrome (Correct answer)
- Hypoxic-ischemic encephalopathy grade I
- Normal preterm variant
Correct answer: Ohtahara syndrome
Burst-suppression in a neonate (outside therapeutic hypothermia) is a hallmark of Ohtahara syndrome (early infantile epileptic encephalopathy).
Question 5: Which epileptiform feature specifically distinguishes a true spike from a sharp wave on EEG?
- Duration less than 70 ms vs. 70–200 ms (Correct answer)
- Amplitude greater than 200 µV
- Occurrence only during NREM sleep
- Presence of a following slow wave
Correct answer: Duration less than 70 ms vs. 70–200 ms
By convention, a spike has a duration of less than 70 ms, whereas a sharp wave has a duration of 70–200 ms; both may be followed by a slow wave.
Question 6: Centrotemporal spikes (rolandic spikes) in a child are associated with which EEG characteristic regarding sleep?
- They disappear entirely during NREM sleep
- They increase in frequency and may become bilateral during NREM sleep (Correct answer)
- They are only seen during REM sleep
- They occur exclusively during drowsiness
Correct answer: They increase in frequency and may become bilateral during NREM sleep
Centrotemporal spikes in benign epilepsy with centrotemporal spikes (BECTS) are markedly activated and may spread bilaterally during NREM sleep.
Question 7: A patient has recurrent brief lapses with 3-Hz spike-and-wave that are abruptly terminated by photic stimulation. This response pattern is called:
- Photomyogenic response
- Photoparoxysmal response (Correct answer)
- Fixation-off sensitivity
- Scotosensitivity
Correct answer: Photoparoxysmal response
A photoparoxysmal response refers to generalized epileptiform discharges (spike-and-wave) triggered by intermittent photic stimulation, distinct from the non-epileptiform photomyogenic response.
EEG Abnormal Epileptiform Patterns 4
Which EEG pattern is characterized by bilateral synchronous 3-Hz spike-and-wave discharges that are typically enhanced by hyperventilation?