Electroclinical Features of Generalized Paroxysmal Fast Activity in Typical Absence Seizures

Generalized paroxysmal fast activity (GPFA) is a diffuse, paroxysmal, frontal predominant activity described in patients with generalized epilepsies. Studies specifically focusing on electroclinical features of typical absence seizures in children have not reported any GPFA-like features. We sought to identify GPFA in children with typical absence seizures, study its incidence, characteristic electroclinical features, and effect on their epilepsy.

We performed a retrospective review of electroencephalograms of children with diagnosis of absence epilepsy. A total of 173 subjects were identified. In subjects with GPFA on their electroencephalograms, GPFA characteristics were collected (i.e., predominant location, duration, amplitude, frequency, provocation factors, and if GPFA was followed by spike-wave discharges). In GPFA-positive subjects, further data sets were collected examining their demographics, duration of epilepsy, and pharmacoresponsiveness to epilepsy.

Generalized paroxysmal fast activity was identified in 10 subjects (5.78%) with female to male ratio of 9:1. Median age of subjects was 17 years, and median duration of illness was 9.5 years. Mean maximum GPFA amplitude was 88.3 μV with posterior predominance in 9/10 subjects. Generalized paroxysmal fast activity frequency ranged between 11 and 20 Hz with duration of 1 to 4 seconds. Generalized paroxysmal fast activity was provoked with eye closure, hyperventilation, and photic stimulation. Antiseizure medications had no effect on GPFA, and epilepsy was well controlled in most subjects.

Generalized paroxysmal fast activity is uncommon in children with typical absence seizures and has medium voltage, posterior predominance, and marked female preponderance. Generalized paroxysmal fast activity is seen during both pharmacoresponsive and drug-resistant epilepsy, and is not affected by antiseizure medications. It may serve as an independent marker of lifelong epilepsy.