Spectrum of motor responses elicited by electrical stimulation of primary motor cortex: A polygraphic study in patients with epilepsy

Surface-electromyography characteristics of clonic seizures with no scalp-EEG correlate: A comparative analysis with tremors

INTRODUCTION

Clonic seizures are characterized by twitching movements at a frequency of 0.2-5 Hz. The clonic "twitch" is produced by a brief synchronized contraction of agonist and antagonist muscles, followed by a synchronized silent period. In this study, we aimed to compare the surface-electromyography (sEMG) characteristics of scalp-EEG negative clonic seizures with those of nonepileptic movements like tremors that can resemble clonic seizures.

METHODS

We retrospectively identified patients who were diagnosed with scalp-EEG negative clonic seizures or tremors. We only included patients (n = 6) who were monitored simultaneously with video-EEG and sEMG electrodes. sEMG was placed on agonist and antagonist muscles of the affected extremity using a standardized placement system developed at our institution. We analyzed the following characteristics of sEMG bursts: the relationship between agonist and antagonist muscles and the temporal evolution of burst duration, burst amplitude, and burst frequency.

RESULTS

The following sEMG characteristics were observed: (i) sEMG bursts and corresponding silent periods were synchronous between agonist and antagonist muscles in clonic seizures. In tremors, an alternating pattern was seen. (ii) sEMG burst amplitude increased during the first 10 s of clonic seizures. There was no significant change in tremors. (iii) sEMG burst duration increased from the beginning to end of clonic seizures. There was no significant change in tremors. (iv) sEMG burst frequency decreased from the beginning to end of clonic seizures due to increased burst and silent period duration. There was no consistent change in burst frequency in tremors. (v) sEMG burst duration of ≥250 ms was indicative of a clonic seizure with a >90% positive predictive value.

CONCLUSIONS

Our study describes characteristic sEMG features of clonic seizures without scalp-EEG correlates, which can be used as an objective biomarker in distinguishing these from nonepileptic movements such as tremors.

SEEG guided mapping of primary motor cortex in children with epilepsy

BACKGROUND

Direct cortical electrical stimulation remains the gold standard for delineation of the primary motor cortex in patients with drug-resistant epilepsy (DRE) undergoing epilepsy surgery evaluation OBJECTIVE: This study aimed to explore the efficacy and safety of functional motor mapping through Stereo-EEG (SEEG) electrode contacts in children with DRE at our institute.

METHODS

We performed a retrospective analysis of children who underwent SEEG evaluation and functional cortical mapping via bipolar electrical stimulation at our institution between July 2020 and June 2024. Detailed clinical, radiological and neurophysiological variable were extracted; qualitative and quantitative variables were summarized using appropriate descriptive statistics.

RESULTS

A total of 29 patients underwent functional cortical motor mapping via SEEG with the mean age of 12.5 years (standard deviation, 4.1). Stimulation was performed using 50 Hz bipolar electrical stimulation. Succesful motor mapping was reported in 28 patients (96.6 %). The median lowest current threshold for a motor response was 2 mA. The spectrum of motor responses reported included: tonic/dystonic (26), clonic (6), and jerk/jitteriness (1). Afterdischarges were noted in 14 patients (48.3 %) and seizures were seen in 5 patients (17.2 %).

CONCLUSIONS

SEEG guided electrical stimulation of motor cortex is feasible and safe for functional cortical mapping in children with epilepsy.

Semiology and Neurophysiology of Clonic Seizures: A Report of 39 Patients

Background and Objectives

Clonic seizures are currently defined as repetitive and rhythmic myoclonic contractions of a specific body part, producing twitching movements at a frequency of 0.2-5 Hz. There are few studies in the literature that have reported a detailed analysis of the semiology, neurophysiology, and lateralizing value of clonic seizures. In this article, we aim to report our findings from a retrospective review of 39 patients.

Methods

We identified 39 patients (48 seizures) from our center who had been admitted with clonic seizures between 2016 and 2022. We performed a retrospective review of their video-EEG recordings for semiology and ictal EEG findings. Seventeen patients also had simultaneous surface-EMG (sEMG) electrodes placed on affected body parts, which were analyzed as well.

Results

The most common initial affected body parts were face, arm, and hand. In most of the cases, seizures propagated from lower face to upper face and distal hand to proximal arm. The most common seizure-onset zone was the perirolandic region, and the most common EEG seizure pattern was paroxysmal rhythmic monomorphic activity. The lateralizing value for EEG seizure onset to contralateral hemisphere in unilateral clonic seizures (n = 39) was 100%. All seizures recorded with sEMG electrodes demonstrated synchronous brief tetanic contractions of agonists and antagonists, alternating with synchronous silent periods. Arrhythmic clonic seizures were associated with periodic epileptiform discharges on the EEG, whereas rhythmic clonic seizures were associated with paroxysmal rhythmic monomorphic activity. Overall, the most common etiology was cerebrovascular injuries, followed by tumors.

Discussion

Clonic seizures are characterized by synchronized brief tetanic contractions of agonist and antagonistic muscles alternating with synchronized silent periods, giving rise to the visible twitching. The most common seizure onset zone is in the perirolandic region, which is consistent with the symptomatogenic zone being in the primary motor area. The lateralizing value of unilateral clonic seizures for seizure onset in the contralateral hemisphere is 100%.