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October 27, 2023
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Yamada, Thoru, and Elizabeth Meng. Practical Guide for Clinical Neurophysiologic Testing: EEG. Available from: Wolters Kluwer, (2nd Edition). Wolters Kluwer Health, 2017.

Interictal epileptiform discharges (IED’s) are helpful in localizing seizure onset but do not hold the same diagnostic value as the actual seizure captured on an EEG.

Capturing IEDs on the EEG will vary depending on several factors such as seizure type, age of the patient, and seizure frequency. Detection of IEDs differs depending on the origin of the epileptiform activity and some may not be detected by scalp electrodes at all.

Recording N2 sleep on EEG, or using the provocation method of sleep deprivation increases the yield of IEDs, and this is especially true in children. NI and N2 sleep are essential for activating interictal epileptiform discharges (IEDs). During awake and REM sleep recordings the IEDs are decreased or abolished. Some epileptic syndromes have dramatically increased IEDs in sleep like CSWS, Landau–Kleffner syndrome, and BECTS.

What are the classic IED’s seen in patients with the generalized adolescent epilepsy of Juvenile Myoclonic Epilepsy?
Polyspike and polyspike-wave discharges
Spike or spike-wave discharges
Extremely high-amplitude polymorphic delta
Correct Answer: 

Interictal EEG patterns of JME consist of generalized polyspike and polyspike-wave discharges with frontocentral predominance. These patterns are not distinguishable from other idiopathic generalized epilepsies but may include more polyspike components. Like other idiopathic seizures, background activity is usually normal. Spike-wave or polyspike-wave bursts are usually faster than the typical 3-Hz spike waves seen in absence seizures, but in some patients, 2.5- to 3-Hz spike-wave bursts may occur that are indistinguishable from typical absence seizures.

Juvenile myoclonic epilepsy is among the more common pediatric epilepsy syndromes, arising in adolescence with possible persistence into adulthood. Clinically it is marked by myoclonic jerks, more often in the morning, and on EEG you may see a classic, intermittent 4-6 Hz generalized spike or polyspike and slow wave pattern.

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