Abstracts

Rationale: Despite all efforts for optimizing epilepsy management in children over the past decades, there is no clear consensus regarding whether to treat or not to treat epileptiform discharges after a first unprovoked seizure, or the optimal duration of therapy with antiseizure medication (ASM). Defining what should be considered as a pathological EEG discharge that requires treatment on scalp EEG is therefore highly needed.This retrospective study aimed to identify whether the electrographic finding of ripples/ high frequency oscillations (HFOs) in coexistence with interictal epileptiform discharges in routinely acquired scalp EEG is associated with a higher risk of seizure recurrence and could be used as a prognostic marker. Methods: Children presenting with new onset seizures to Children Medical Center- Dallas in 2015, who were not on ASM, and who had focal epileptiform discharges on an awake and sleep EEG recorded with sample frequency of 500 HZ, were identified by review of electronic database. 100 children were selected at random from this group and enrolled into the study.EEGs were analyzed blinded to patient’s data. HFOs were visually identified using a method devised from methods used in previous studies (Kobayashi et al., 2010; Nariai et al., 2018; van Klink et al., 2016). Five spikes or sharp waves were examined for each patient measuring duration, amplitude, frequency, activation by sleep, and presence of HFOs. Patients charts were then reviewed as regards seizure recurrence in the first two years, start and duration of ASM. Results: The average age of patients was 6.3 yrs (range 3 mos– 18 yrs). HFOs were visually identified in 20% of the studied epileptiform discharges with inter-rater reliability of 100% for identification of HFO negative discharges and 88% agreement for HFOs.HFOs were found more often in the younger age group (44.4%, 15%, 20% and 4.5 % in age groups <2 yrs, 2-5 yr, 5-10 yrs and >10 yrs respectively). When present, HFOs were identified in all studied epileptiform discharges whether spikes or sharp waves for the patient. They were identified more often with higher amplitude spikes/sharp waves- 13.9% for spikes/sharp waves with amplitude100-150uv and 31.9% for those >150 uV compared to 3.8% for spikes/sharp waves 50-100uv .Patients with HFOs were more likely to have recurrence of seizures during the first year after diagnosis; 88.9% vs 46.5% for HFO negative patients (P <0.003), and to continue to have seizures after two years; 80% vs 20% (P<0.0001). There was no statistically significant difference between the two groups as regards continuing on anti-seizure medications after 2 years. Conclusions: HFOs can be visually identified on routinely acquired scalp EEG, and their presence predicted risk for seizure recurrence. Including analysis for HFOs in routine EEG interpretation increases the yield of the study, and may help guide the decision to start or discontinue ASM for children with epilepsy. In the future, this may also help to identify the pathological EEG discharges with deleterious effect on the growing brain and may set a new target for management of epilepsy.  Funding: No funding