Authors :
Presenting Author: Mahtab Rostamihosseinkhani, MD – University of Alabama at Birmingham
Rebekah Chatfield, BS – University of Alabama at Birmingham
Rachel Smith, PhD, MS, BS – University of Alabama at Birmingham
Benjamin Cox, MD – University of Alabama at Birmingham
Rationale:
Single-pulse electrical stimulation (SPES) using stereo-EEG (sEEG) electrodes can generate corticocortical evoked potentials (CCEPs). These responses are increasingly used to investigate brain connectivity and identify the seizure-onset zone in patients with drug-resistant epilepsy. It is important, however, to assess how this stimulation may affect the seizure network. This study aims to determine whether SPES has any impact on interictal activity or recorded seizures.Methods:
We applied SPES in 30 patients with drug-resistant epilepsy undergoing sEEG monitoring for seizure localization. Stimulation was delivered between all paired electrode contacts using standard parameters (5 mA, 1 Hz, 300 μs pulse width) over 30 seconds. One-hour segments of sEEG immediately before and after stimulation were reviewed. Stimulation-induced seizures were assessed in all patients. Interictal spike rates (spikes/minute) and seizure counts before and after stimulation were manually counted by expert reviewers in a subset of 21 patients with available pre- and post-stimulation baseline recordings. The colocalization of stimulation-induced seizures with spontaneous seizures was also noted. A paired t-test was used to compare pre- and post-stimulation spike rates, and McNemar’s test was applied to assess changes in seizure occurrence.Results:
Spike rates did not significantly differ from pre-SPES (mean 32.1 spikes/min) to post-SPES (mean 28.4 spikes/min), with a mean decrease of 3.27 spikes/min across patients (P = 0.24; see Fig. 1). In the hour pre- and post-SPES one patient experienced a seizure only after stimulation, two had seizures only before stimulation, and the remaining eighteen had no seizures during either time window. The difference in seizure frequency before and after stimulation was not statistically significant (P = 0.56). Eleventh of the 30 patients had SPES-induced seizures (5 with only subclinical, 4 with only clinical, 2 with both types). Among these, there was an average of 1.64 subclinical and 0.55 clinical seizures. All SPES-seizures colocalized with the spontaneous seizures except in two patients— one localized to the early propagation zone and another localized to a non-involved area.
Conclusions:
This study provides preliminary evidence that SPES does not significantly alter interictal spike rates or seizures. Although our sample size was limited, further research involving larger groups is needed to draw more definitive conclusions. Demonstrating the safety of SPES remains a key step toward its wider use in clinical and research applications.
Funding:
AES Junior Investigator Award (1042632) and the CURE Epilepsy Taking Flight Award (1061181).