Consistent topography and amplitude symmetry are more typical than morphology of epileptiform discharges in genetic generalized epilepsy

- 24-h ambulatory electroencephalograms were done in a cohort of patients diagnosed with genetic generalized epilepsy.
- The typical epileptiform abnormalities were evaluated quantitatively to demonstrate the spectrum of common and rare EEG characteristics in GGE.
- Awareness of the most consistent EEG features (topography and amplitude symmetry) and their variations is important to avoid misdiagnosis.

ObjectiveTo provide a quantitative evaluation of typical electroencephalographic (EEG) abnormalities in genetic generalized epilepsy (GGE).MethodsWe prospectively performed 24-h ambulatory EEG recordings in a cohort of patients with GGE. The diagnosis was established according to the International League Against Epilepsy criteria. Details of all epileptiform discharges across the 24-h time scale were entered into an electronic database. We carried out descriptive statistics to provide a quantitative breakdown of typical EEG abnormalities.ResultsA total of 6923 epileptiform discharges from 105 abnormal 24-h ambulatory EEGs were analyzed. 96% of discharges were symmetric in amplitude with fronto-central maximum topographically. Only 24% of the paroxysms had typical morphology while 43% were regular. Photoparoxysmal response, eye-closure sensitivity and hyperventilation-induced generalized paroxysms were less common in around 10%, whereas occipital intermittent rhythmic delta activity was very rare (2%).ConclusionOur results indicate that generalized discharges with symmetric amplitude and fronto-central maxima are the most consistent findings in GGE, and other features are observed less frequently.SignificanceEpileptiform discharges displaying highly consistent amplitude symmetry coupled with fronto-central topography should provoke consideration of GGE. Recognition of variations from typical abnormalities is important to avoid the risk of misdiagnosis and delayed diagnosis.