EEG - Electroencephalography Pediatric and Neonatal EEG Questions and Answers 1 — Questions and Answers
Question 1: An EEG is performed on a 32-week conceptional age premature infant. During quiet sleep, the recording shows bursts of high-amplitude mixed frequencies lasting 3-10 seconds, separated by periods of marked attenuation (<25 µV) lasting 10-20 seconds. This pattern is best described as:
- Tracé alternant
- Tracé discontinu (Correct answer)
- Burst-suppression
- Hypsarrhythmia
Correct answer: Tracé discontinu
Tracé discontinu is the characteristic EEG pattern of quiet sleep in premature infants between approximately 30 and 34 weeks conceptional age. It consists of bursts of mixed-frequency activity separated by interburst intervals of significant voltage attenuation, typically less than 25 µV. [1, 2, 3] Tracé alternant is seen in older infants (around 34-44 weeks) and has a higher interburst interval amplitude (>25 µV). Burst-suppression is a profoundly abnormal pattern associated with severe encephalopathy. Hypsarrhythmia is a chaotic, high-voltage, disorganized pattern seen in infants with West syndrome.
Question 2: A 7-year-old child with normal development presents with new-onset seizures, often occurring shortly after falling asleep. The seizures involve twitching on one side of the face and drooling. The interictal EEG shows high-amplitude, diphasic sharp-and-slow wave complexes that are most prominent over the left centrotemporal region and increase significantly during drowsiness. What is the most likely diagnosis?
- Childhood Absence Epilepsy
- Lennox-Gastaut Syndrome
- Self-Limited Epilepsy with Centrotemporal Spikes (SeLECTS) (Correct answer)
- Juvenile Myoclonic Epilepsy
Correct answer: Self-Limited Epilepsy with Centrotemporal Spikes (SeLECTS)
The clinical description of focal seizures involving the face and the specific EEG finding of high-amplitude sharp waves in the centrotemporal (rolandic) region, which are activated by sleep, are pathognomonic for Self-Limited Epilepsy with Centrotemporal Spikes (SeLECTS), formerly known as Benign Rolandic Epilepsy. [16, 18] Childhood Absence Epilepsy features generalized 3 Hz spike-wave discharges. [12] Lennox-Gastaut Syndrome and Juvenile Myoclonic Epilepsy have different clinical and EEG characteristics.
Question 3: Which of the following electrographic features is most characteristic of an ictal event (electrographic seizure) in a full-term neonate?
- Generalized, synchronous 3 Hz spike-and-wave discharges.
- A sustained, rhythmic, evolving pattern of sharp waves or delta activity lasting more than 10 seconds. (Correct answer)
- Intermittent, asynchronous bursts of high-voltage slow waves mixed with spikes (Hypsarrhythmia).
- Bilaterally synchronous and symmetric sleep spindles.
Correct answer: A sustained, rhythmic, evolving pattern of sharp waves or delta activity lasting more than 10 seconds.
The gold standard for identifying a neonatal electrographic seizure is the presence of a sustained, rhythmic discharge that shows clear evolution in frequency, morphology, or location and lasts for at least 10 seconds. [5, 26] Neonatal seizures are typically focal in onset and can consist of various morphologies, including rhythmic delta or sharp activity. [5] Generalized 3 Hz spike-and-wave is typical of absence seizures in older children, hypsarrhythmia is an interictal pattern, and sleep spindles are normal sleep architecture.
Question 4: A 6-month-old infant is brought in for evaluation of developmental regression and clusters of flexor spasms that occur upon waking. The EEG shows a continuous, chaotic, and disorganized pattern of very high-voltage, asynchronous slow waves with multifocal spikes and sharp waves. This EEG pattern is called:
- Burst-suppression
- Tracé alternant
- Extreme spindle coma
- Hypsarrhythmia (Correct answer)
Correct answer: Hypsarrhythmia
The described EEG pattern is the classic presentation of hypsarrhythmia. It is characterized by its chaotic, disorganized, and high-amplitude ('mountainous') appearance with asynchronous slow waves and multifocal spikes. [8, 9, 10] This pattern is the interictal hallmark of West Syndrome, which includes the clinical triad of infantile spasms, hypsarrhythmia on EEG, and developmental delay or regression. [10]
Question 5: In a healthy 3-year-old child, the posterior dominant rhythm (PDR) during relaxed wakefulness with eyes closed is expected to have a frequency of approximately:
- 4-5 Hz
- 10-12 Hz
- 8-9 Hz (Correct answer)
- 6-7 Hz
Correct answer: 8-9 Hz
The posterior dominant rhythm (PDR), or alpha rhythm, matures with age. It begins around 3-4 Hz at a few months of age and should reach the alpha frequency range of 8 Hz by approximately 3 years of age. [2] A PDR of 4-5 Hz would be too slow for a 3-year-old, while 10-12 Hz is more typical of an older child or adult. 6-7 Hz would be expected around 12 months of age.
Question 6: A 5-year-old girl is evaluated for frequent staring spells. During hyperventilation, the EEG shows a 12-second burst of generalized, synchronous, and symmetric 3 Hz spike-and-wave discharges with an abrupt onset and offset. The patient was unresponsive during the event. This EEG finding is the classic hallmark of:
- Lennox-Gastaut Syndrome
- Childhood Absence Epilepsy (Correct answer)
- Benign Rolandic Epilepsy
- Juvenile Myoclonic Epilepsy
Correct answer: Childhood Absence Epilepsy
The classic electroclinical signature of Childhood Absence Epilepsy (CAE) is the presence of generalized, symmetric, 3 Hz spike-and-wave discharges that are associated with clinical absence seizures (staring, unresponsiveness). [12, 19, 22] These events are often provoked by hyperventilation, have an abrupt start and stop, and occur in otherwise neurologically normal children. The other listed syndromes have distinctly different EEG and clinical features.
EEG - Electroencephalography Pediatric and Neonatal EEG Questions and Answers 1
An EEG is performed on a 32-week conceptional age premature infant.
During quiet sleep, the recording shows bursts of high-amplitude mixed frequencies lasting 3-10 seconds, separated by periods of marked attenuation (<25 µV) lasting 10-20 seconds.
This pattern is best described as: