Paroxysmal fast activity is a biomarker of treatment response in deep brain stimulation for Lennox–Gastaut syndrome

Objective Epilepsy treatment trials typically rely on seizure diaries to determine seizure frequency, but these are time‐consuming and difficult to maintain accurately. Fast, reliable, and objective biomarkers of treatment response are needed, particularly in Lennox–Gastaut syndrome (LGS), where high seizure frequency and comorbid cognitive and behavioral issues are additional obstacles to accurate diary‐keeping. Here, we measured generalized paroxysmal fast activity (GPFA), a key interictal electrographic feature of LGS, and correlated GPFA burden with seizure diaries during a thalamic deep brain stimulation (DBS) treatment trial (Electrical Stimulation of the Thalamus in Epilepsy of Lennox–Gastaut Phenotype [ESTEL]). Methods GPFA and electrographic seizure counts from intermittent, 24‐h electroencephalograms (EEGs) were compared to 3‐month diary‐recorded seizure counts in 17 young adults with LGS (mean age ± SD = 24.9 ± 6.6) in the ESTEL study, a randomized clinical trial of DBS lasting 12 months (comprising a 3‐month baseline and 9 months of postimplantation follow‐up). Results Baseline median seizures measured by diaries numbered 2.6 (interquartile range [IQR] = 1.4–5) per day, compared to 284 (IQR = 120.5–360) electrographic seizures per day, confirming that diaries capture only a small fraction of seizure burden. Across all patient EEGs, the average number of GPFA discharges per hour of sleep was 138 (IQR =72–258). GPFA duration and frequency, quantified over 2‐h windows of sleep EEG, were significantly associated with diary‐recorded seizure counts over 3‐month intervals (p