Electroclinical spectrum of generalized paroxysmal fast activity in adults without epileptic encephalopathy

Introduction Generalized paroxysmal fast activity (GPFA) is a rare and underreported EEG pattern known to be related to epileptic encephalopathy. We aimed to investigate the electroclinical spectrum of GPFA along with other atypical EEG features in patients without epileptic encephalopathy in routine EEG practice. Methods Outpatient EEG records of Hacettepe University Hospital were retrospectively reviewed between 2010 and 2020. Patients >= 18 years old with GPFA without epileptic encephalopathy were included. Electroclinical features of GPFA were analyzed. Atypical EEG features, epileptiform K-complexes and sleep spindles, and generalized polyspike train (GPT) were also investigated in this cohort. Results Most of the 19 included patients had refractory epilepsy (68%), while 16% were seizure-free. Generalized epilepsy (GE) was present in 58% of patients, and the rest had structural-focal epilepsy (26%), combined generalized and focal epilepsy (11%), or childhood occipital epilepsy (COE) (5%). Atypical EEG features with full atypical morphology were found in 91% of patients with GE. All patients with GPFA provoked by sleep had epileptiform K-complexes. The presence of GPT was not different between the GE and non-GE groups and was higher in patients with GPFA occurring only during sleep (p = 0.017). In two patients, GPFA frequency increased postictally. A transition from fixation-off sensitivity to GPFA occurred in a patient with COE. Conclusion In this study, GPFA had a wide diagnostic range from focal to generalized epilepsy. The association of GPFA with other electroclinical features was of importance mostly for sleep outcomes; this finding might lead to a better understanding of epileptogenesis.