Objective: Genetic testing has become a routine part of the diagnostic workup in children with early onset epilepsies. In the present study, we sought to investigate a cohort of adult patients with epilepsy, to determinate the diagnostic yield and explore the gain of personalized treatment approaches in adult patients. Methods: Two hundred patients (age span = 18-80 years) referred for diagnostic gene panel testing at the Danish Epilepsy Center were included. The vast majority (91%) suffered from comorbid intellectual disability. The medical records of genetically diagnosed patients were mined for data on epilepsy syndrome, cognition, treatment changes, and seizure outcome following the genetic diagnosis. Results: We found a genetic diagnosis in 46 of 200 (23%) patients. SCN1A, KCNT1, and STXBP1 accounted for the greatest number of positive findings (48%). More rare genetic findings included SLC2A1, ATP6A1V, HNRNPU, MEF2C, and IRF2BPL.Gene-specific treatment changes were initiated in 11 of 46 (17%) patients (one with SLC2A1, 10 with SCN1A) following the genetic diagnosis. Ten patients improved, with seizure reduction and/or increased alertness and general well-being. Significance: With this study, we show that routine diagnostic testing is highly relevant in adults with epilepsy. The diagnostic yield is similar to previously reported pediatric cohorts, and the genetic findings can be useful for therapeutic decisionmaking, which may lead to better seizure control, ultimately improving quality of life.

Objective. To characterize in detail the electroclinical features of typical absence seizures and elucidate whether EEG or semiology features, alone or in combination, can predict long‐term therapeutic outcome. Methods . We analysed video‐EEG recordings from 213 typical absence seizures from 61 patients with idiopathic generalized epilepsy. We extracted semiological features, in addition to hallmark manifestations (motor/behavioural arrest, non‐responsiveness), their location, timing and frequency. We evaluated the duration and frequency of generalized spike‐wave discharges and the presence of polyspikes. We used a supervised machine‐learning approach (random forest) to search for classifier features for long‐term therapeutic outcome (>one year). Results. Besides the hallmark manifestations, additional semiological features were identified in 87% of patients (75% of seizures). The most common additional semiological features were automatisms and eye blinking (observed in 45% and 41.5% of seizures, respectively). Automatisms were associated with longer seizure duration, and oral automatisms occurred earlier compared to limb automatisms (4.03 vs. 6.19 seconds; p=0.005). The mean duration of the ictal spike‐wave discharges was nine seconds, and the median frequency was 3 Hz. Polyspikes occurred in 46 seizures (21.6%), in 19 patients (31%). Median follow‐up was five years, and 73% of the patients were seizure‐free at the end of the follow‐up. None of the semiological features, alone or in combination, were predictors of therapeutic outcome. The only significant classifier was the presence of polyspikes, predicting a non‐seizure‐free outcome with an accuracy of 73% (95% CI: 70‐77%), positive predictive value of 92% (95% CI: 84‐98%) and negative predictive value of 60% (95% CI: 39‐81%). Significance. Semiological features, in addition to behavioural arrest and non‐responsiveness, are common in typical absence seizures, but they do not predict long‐term therapeutic outcome. The presence of polyspikes has a high positive predictive value for unfavourable therapeutic outcome, and their presence should therefore be included when reporting EEGs in patients with typical absence seizures.