Electrophysiological characteristics and syndrome specificity of generalized paroxysmal fast activity in genetic generalized epilepsy.

OBJECTIVE: The characteristics of generalized paroxysmal fast activity (GPFA) in genetic generalized epilepsy (GGE) have been reported previously, but its electroclinical features and syndrome specificity remain unclear. This study explored the characteristics of GPFA based on the EEG data of patients with GGE. METHODS: Clinical and EEG data were retrospectively collected from GGE patients who presented with GPFA on their EEG. Electroclinical characteristics of GPFA, including its incidence rate, age at first detection on EEG, period of occurrence, and inducing factors, were analyzed across different GGE syndromes. RESULTS: Seventy-nine GGE patients presented with GPFA on EEG, most commonly in epilepsy with eyelid myoclonia (EEM) and unclassified GGE. GPFA was detected only during the wakefulness in 73.4% of the patients. Photosensitivity was observed in 48.1% of the patients with GPFA, and eye closure sensitivity was observed in 75.9%. In 45.6% (36/79) of the patients, GPFA was accompanied by generalized epileptic seizures, including 25 with eyelid myoclonia with or without absence seizures and 11 with myoclonic seizures. A retrospective review of the serial EEGs of 53 patients revealed that GPFA persisted in 34 patients, whereas it presented transiently in 19. Specifically, GPFA persisted in 82.4% of EEM patients and 88.9% of epilepsy with generalized tonic-clonic seizures alone (GTCA) patients. CONCLUSION: GPFA is an important EEG marker of GGE, with a higher prevalence in patients with unclassified GGE and EEM. GPFA can be induced by eye closure and inter mitten photic stimulation (IPS) and is detectable by both interictal and ictal EEG. GPFA can either be present transiently or persist on the EEGs of GGE patients.