Generalized onset seizures with focal evolution (GOFE) – a largely unknown ictal variation in genetic generalized epilepsies.

• Focal electroclinical features at onset of generalized seizure are well-known. • In contrary, knowledge on generalized onset seizures with focal evolution is sparse. • We report detailed ictal EEG and semiological characteristics of five such patients. • As focal signs may be prominent, risk of misclassification as focal seizure is high. • In generalized onset seizures, focal electroclinical features seem to be a variant. At onset of generalized seizures, focal electroclinical features are commonly seen, while generalized onset seizures with focal evolution (GOFE) are largely unknown bearing the risk of misclassification. In two German epilepsy-centers, patients with GOFE documented by video-EEG monitoring (VEM) between 2017 and 2022 were identified retrospectively. In addition to analysis of ictal electroclinical features, detailed epilepsy and family history, response to antiseizure medication (ASM), and findings from neuroimaging were considered. We identified five patients with GOFE, three females, age 14 to 22 years. All patients developed genetic generalized epilepsy in childhood or adolescence, each presenting with two or three generalized seizure types. In each of the five patients, one GOFE was recorded by VEM. At onset, EEG seizure patterns were characterized by generalized spike-wave discharges at 2.5 to 3.5/ sec for 9 to 16 s followed by focal evolution of the discharges. Interictally, all patients presented with generalized spike-wave discharges without focal abnormalities. Semiology at onset was behavioral arrest in two patients and generalized increase in tone in one, while two onsets were clinically inapparent. Semiological signs during focal evolution were variable, comprising head and body version, figure 4 sign, unilateral arm clonic activity, and staring with oral automatisms. In one case, focality involved both hemispheres successively. Prominent focal semiological features in GOFE carry a high risk of misclassification as focal seizures and epilepsy and thus wrong choice of ASM. This calls for low-threshold VEM if any doubts of focal genesis of seizures exist. [ABSTRACT FROM AUTHOR]