Biceps electromyography in dialeptic and automotor seizures with and without secondary generalization

•This study analyzed biceps muscle activity during the course of automotor and dialeptic seizures.•A new seizure evolution with a generalized tonic-unilateral clonic pattern was noted in dialeptic seizures.•A prominent uni- or bilateral spindle-shaped increase of muscle tone could serve as predictor for generalizing seizures.

ObjectiveLocalization of seizure onset during presurgical video-EEG monitoring is indispensable for successful epilepsy surgery. Sometimes analysis of ictal EEG and video fails to identify this zone. Therefore, this study explored the hypothesis that ictal EMG recordings contribute to the lateralization or localization of focal epilepsy.MethodsAll patients with automotor or dialeptic seizures with or without secondary generalization were prospectively included during presurgical video-EEG monitoring over a 5 years study period. We analyzed characteristics of ictal biceps EMG and compared the results to EEG and video findings.Results79 patients with 185 seizures were included (51.9% male; 73.5% automotor and 26.5% dialeptic seizures; 24.3% seizures secondarily generalized). Even in dialeptic seizures, muscle tone increased bilaterally within seconds after EEG seizure onset (66.7%) without clinical movements. Bilateral “spindle-shaped” EMG activity during the automotor phase predicted secondary generalization in 88.7%. Increase of muscle activity in the contralateral side of the body in the beginning of the secondarily generalized tonic-clonic phase was detected in 78.1% after automotor seizures whereas this phenomenon was less pronounced after dialeptic seizures (69.2%). 38.5% of dialeptic seizures evolved into generalized tonic-unilateral clonic seizures.ConclusionIctal EMG recordings provide lateralizing signs especially in secondarily generalized automotor seizures. In addition, the study suggested that secondary generalization in automotor seizures is determined early already during the automotor phase. Dialeptic seizures can evolve only unilaterally into a tonic-clonic seizure while the other side of the body remains tonic.SignificanceIctal biceps EMG can provide further information regarding lateralization of epileptic seizures.