EEG - Electroencephalography Abnormal Epileptiform Patterns Questions and Answers

Question 1

An 8-year-old child presents with frequent staring spells. The EEG recording shows bursts of generalized, synchronous, and symmetric 3 Hz spike-and-wave discharges that are easily provoked by hyperventilation. What is the most likely clinical correlation?

Accepted Answer

Childhood absence epilepsy

Answer

The classic EEG signature for typical childhood absence epilepsy is generalized, symmetric 3 Hz spike-and-wave discharges, often induced by hyperventilation, which correlates clinically with brief staring spells. Lennox-Gastaut syndrome presents with slow (<2.5 Hz) spike-and-wave, Benign Rolandic epilepsy shows focal centrotemporal spikes, and Juvenile myoclonic epilepsy typically has faster (>3 Hz) polyspike-and-wave discharges.

Question 2

According to the American Clinical Neurophysiology Society (ACNS) guidelines, an epileptiform discharge is classified as a 'sharp wave' based on which of the following duration ranges?

Accepted Answer

70-200 milliseconds

Answer

A sharp wave is defined as a transient with a pointed peak and a duration of 70 to 200 milliseconds. Discharges with a duration of less than 70 ms are classified as spikes, and waves lasting longer than 200 ms are considered slow waves.

Question 3

A 9-month-old infant is evaluated for clusters of sudden, brief flexor spasms. The interictal EEG shows a chaotic, high-voltage, and disorganized pattern of asynchronous slow waves and multifocal spikes. Which of the following terms best describes this EEG pattern?

Accepted Answer

Hypsarrhythmia

Answer

Hypsarrhythmia is the characteristic interictal EEG pattern associated with Infantile Spasms (West Syndrome). It is defined by its disorganized, high-amplitude, and chaotic appearance, with a mix of random slow waves and multifocal spikes.

Question 4

An EEG on a 10-year-old child shows high-amplitude, diphasic sharp waves that occur independently over the centrotemporal regions (C3/T3 and C4/T4). The discharges become significantly more frequent during drowsiness and sleep. This pattern is pathognomonic for which epilepsy syndrome?

Accepted Answer

Self-limited Epilepsy with Centrotemporal Spikes (SeLECTS)

Answer

Self-limited Epilepsy with Centrotemporal Spikes (SeLECTS), formerly known as Benign Rolandic Epilepsy, is characterized by these specific centrotemporal spikes, which show a marked increase during sleep. The location of the discharges is key to this diagnosis.

Question 5

An EEG performed on a patient with an acute left-hemispheric stroke shows stereotyped sharp waves recurring every 1-1.5 seconds, confined to the left cerebral hemisphere. This pattern is best described as:

Accepted Answer

Periodic Lateralized Discharges (PLEDs)

Answer

This pattern fits the definition of Periodic Lateralized Discharges (PLEDs), which are stereotyped, periodic complexes that are restricted to one hemisphere. They are often associated with acute structural lesions like stroke or encephalitis. GPDs are bilateral, not lateralized.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Abnormal Epileptiform Patterns Questions and Answers