According to a study published in Epilepsy & Behavior, seizures with habitual motor semiology may be triggered early in diagnostic direct electrical stimulation (DES) during stereoelectroencephalography (SEEG) intracerebral recording for epilepsy presurgical assessment.

Patients with habitual seizures featuring objective motor signs involving the limbs and/or trunk triggered by diagnostic 50-Hz train bipolar stimulation during SEEG were included. A total of 120 habitual seizures triggered by DES during SEEG were included in the final analysis. Spontaneous seizures were recorded on surface video-EEG before SEEG as well as typical noninvasive tests prior to surgery.

Investigators evaluated seizure stimulation parameters, electroclinical data, semiology, and anatomical localization in spontaneous and stimulated seizures. The primary focus was seizure onset, defined as a seizure beginning with a first observable clinical sign (eg, change in motor behavior). Motor behaviors included elementary motor behavior signs (ie, limb tonic posture and/or clonic jerks) and/or complex motor behavior signs (ie, rock, tapping, and twisting).

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A total of 20 habitual seizures triggered during SEEG in 16 patients were associated with initial motor semiology, including either elementary motor signs, complex motor behavior, or both. Biphasic current of 0.5-2.0 milliamperes at a frequency of 50 Hz was used to initiate bipolar stimulations of 2 adjacent electrodes, representing a duration stimulation range of 3.0-5.0 seconds. Clinical seizure onset patterns observed after stimulation included long latency onset (n=7) and short latency onset (n=13), represented by semiology occurring after the stimulation train and semiological expressing occurring during the stimulation train, respectively.

The primary limitation of the analysis includes its small sample size, which may reduce the findings’ generalizability across the population.

“Rather than the usual scenario in spontaneous seizures in which clinical expression is driven by cortical epileptic discharge in short latency seizures,” the researchers wrote, “DES might allow more rapid ignition of the same epileptogenic network predominantly via its corticosubcortical connections, thus effectively producing a “short- cut” to behavioral expression.”

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McGonigal A, Lagarde S, Trébuchon-Dafonseca A, Roehri N, Bartolomei F. Early onset motor semiology in seizures triggered by cortical stimulation during SEEG. Epilepsy Behav. 2018;88:262–267.