[ARTICLE] Electroencephalography in the Diagnosis of Genetic Generalized Epilepsy Syndromes – Full Text

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.

Introduction

Genetic generalized epilepsy (GGE) encompasses several electroclinical syndromes diagnosed and classified according to clinical features and electroencephalographic (EEG) characteristics (1–3). The EEG hallmark of GGE is bilateral synchronous, symmetrical, and generalized spike-wave (GSW) discharges. Polyspikes and polyspike-wave discharges are also commonly seen in GGE. Fixation-off 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).

In this review, we will be discussing the ictal and the interictal EEG abnormalities in GGE. We will also focus on the electrographic differences among different GGE syndromes, factors affecting the yield of EEG, and diagnostic pitfalls.[…]

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Figure 1. Typical interictal epileptiform discharges in genetic generalized epilepsy. Note bilateral, symmetrical, and synchronous spike-wave discharges (A), polyspike-wave discharges (B), and polyspikes (C).