Abstract
Genetic generalized epilepsy (GGE) consists of several syndromes diagnosed and classified on the basis of clinical features and electroencephalographic (EEG) abnormalities. The main EEG feature of GGE is bilateral, synchronous, symmetric, and generalized spike-wave complex. Other classic EEG abnormalities are polyspikes, epileptiform K-complexes and sleep spindles, polyspike-wave discharges, occipital intermittent rhythmic delta activity, eye-closure sensitivity, fixation-off sensitivity, and photoparoxysmal response. However, admixed with typical changes, atypical epileptiform discharges are also commonly seen in GGE. There are circadian variations of generalized epileptiform discharges. Sleep, sleep deprivation, hyperventilation, intermittent photic stimulation, eye closure, and fixation-off are often used as activation techniques to increase the diagnostic yield of EEG recordings. Reflex seizure-related EEG abnormalities can be elicited by the use of triggers such as cognitive tasks and pattern stimulation during the EEG recording in selected patients. Distinct electrographic abnormalities to help classification can be identified among different electroclinical syndromes.
Highlights
Genetic generalized epilepsy (GGE) encompasses several electroclinical syndromes diagnosed and classified according to clinical features and electroencephalographic (EEG) characteristics [1,2,3]
Fixationoff sensitivity (FOS), eye-closure sensitivity, photoparoxysmal response (PPR), epileptiform K-complexes/sleep spindles, and occipital intermittent rhythmic delta activity (OIRDA) are among the spectrum of abnormalities described in GGE [4]
We will focus on the electrographic differences among different GGE syndromes, factors affecting the yield of EEG, and diagnostic pitfalls
Summary
Genetic generalized epilepsy (GGE) encompasses several electroclinical syndromes diagnosed and classified according to clinical features and electroencephalographic (EEG) characteristics [1,2,3]. The EEG hallmark of GGE is bilateral synchronous, symmetrical, and generalized spike-wave (GSW) discharges. A more recent study considered GSW bursts lasting 3 or more seconds, with or without clinical signs, as an absence seizure [8]. The second component is a positive transient of 100–150 ms It is followed by spike 2 of negative polarity lasting 30–60 ms with frontal amplitude maxima. The source localization of epileptiform discharges on dense array EEG in juvenile myoclonic epilepsy (JME) detected activity in the orbitofrontal and medial frontopolar cortex [17]. Frequency of Discharges The typical 3 Hz spike-wave activity characteristic of absence seizures was first described by Gibbs and collaborators [9]. The fast spike-wave activity of >3.5 Hz is usually seen in juvenile myoclonic epilepsy (JME) [19]. The initial frequency is slightly faster and it becomes more stable, slower, and regular [20]
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