Abstract
ObjectiveTo investigate the electroclinical characteristics and the prognostic impact of generalized fast discharges in a large cohort of genetic generalized epilepsy (GGE) patients studied with 24-h prolonged ambulatory electroencephalography (paEEG).MethodsThis retrospective multicenter cohort study included 202 GGE patients. The occurrence of generalized paroxysmal fast activity (GPFA) and generalized polyspike train (GPT) was reviewed. GGE patients were classified as having idiopathic generalized epilepsy (IGE) or another GGE syndrome (namely perioral myoclonia with absences, eyelid myoclonia with absences, epilepsy with myoclonic absences, generalized epilepsy with febrile seizures plus, or GGE without a specific epilepsy syndrome) according to recent classification proposals.ResultsGPFA/GPT was found in overall 25 (12.4%) patients, though it was significantly less frequent in IGE compared with other GGE syndromes (9.3 vs. 25%, p = 0.007). GPFA/GPT was found independently of seizure type experienced during history, the presence of mild intellectual disability/borderline intellectual functioning, or EEG features. At multivariable analysis, GPFA/GPT was significantly associated with drug resistance (p = 0.04) and with a higher number of antiseizure medications (ASMs) at the time of paEEG (p < 0.001) and at the last medical observation (p < 0.001). Similarly, GPFA/GPT, frequent/abundant generalized spike-wave discharges during sleep, and a higher number of seizure types during history were the only factors independently associated with a lower chance of achieving 2-year seizure remission at the last medical observation. Additionally, a greater number of GPFA/GPT discharges significantly discriminated between patients who achieved 2-year seizure remission at the last medical observation and those who did not (area under the curve = 0.77, 95% confidence interval 0.57–0.97, p = 0.02)ConclusionWe found that generalized fast discharges were more common than expected in GGE patients when considering the entire GGE spectrum. In addition, our study highlighted that GPFA/GPT could be found along the entire GGE continuum, though their occurrence was more common in less benign GGE syndromes. Finally, we confirmed that GPFA/GPT was associated with difficult-to-treat GGE, as evidenced by the multivariable analysis and the higher ASM load during history.
Highlights
Generalized paroxysmal fast activity (GPFA) has always been considered one of the electroencephalography (EEG) hallmarks of Lennox-Gastaut syndrome (LGS)
We aimed to investigate generalized fast discharges in a large cohort of genetic generalized epilepsy (GGE) patients studied with prolonged ambulatory EEG (paEEG) in order to clarify their prevalence and identify the electroclinical characteristics and epilepsy syndromes associated with these EEG patterns along the GGE spectrum
Patients were enrolled according to the following inclusion criteria: [1] diagnosis of GGE according to recently proposed criteria; [9] [2] availability of at least one 24 h ambulatory EEG and one standard video EEG; [3] availability of complete clinical documentation in order to adequately review electroclinical features and seizure outcome information; and [4] followup duration of at least 5 years from epilepsy onset to the last medical observation and at least 24 months from paEEG recording to the last medical observation
Summary
Generalized paroxysmal fast activity (GPFA) has always been considered one of the electroencephalography (EEG) hallmarks of Lennox-Gastaut syndrome (LGS). GPFA was later described in genetic generalized epilepsy (GGE) patients exhibiting intermediate phenotypes between classical idiopathic generalized epilepsy (IGE) and epileptic/developmental encephalopathy, with higher rates of poor seizure control and borderline intellectual functioning [2, 3]. Different authors have recently described GPFA in classical IGE syndromes with favorable seizure and neuropsychiatric outcomes, raising questions regarding the real prognostic and electroclinical significance of this EEG pattern along the GGE spectrum [4–6]. In addition to GPFA, a newly described EEG pattern, defined as generalized polyspike train (GPT), has been reported in GGE patients [7]. GPT is characterized by a shorter discharge duration and has been considered a promising biomarker of drug resistance in GGE patients [7, 8]
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