Epilepsy affects about 1% of the population, with roughly 30% of patients with epilepsy
eventually developing drug-resistant epilepsy (DRE). Increasingly, surgery is pursued for
DRE, yielding seizure freedom rates of 50-70%. However, accurate deduction of the
epileptogenic zone (EZ) for surgical planning can be difficult in pediatric DRE,
especially in those cases of multifocal seizures, as is often seen in Tuberous Sclerosis
Complex (TSC), for example. Patients with multifocal epilepsy typically require a period
of pre-surgical invasive EEG monitoring to record spontaneous seizures, the gold standard
for EZ deduction. Unfortunately, the invasive monitoring process may be lengthy, costly
and even fail to reveal a dominant EZ.
Electrical stimulation of induced seizures (ESIS) using stereo EEG (sEEG) has been shown
to be a safe and valid adjunct for EZ delineation in adults with DRE. ESIS can be
implemented within 1-2 days of electrode implantation, while the patient would otherwise
be passively awaiting spontaneous seizures. ESIS typically induces habitual seizures with
few side effects, and there is no data to suggest that ESIS inhibits spontaneous seizures
or prolongs the otherwise clinically-indicated hospital stay. Crucially, published data
show that induced seizures provide information about the EZ that is both convergent with
and unique from that provided by spontaneous seizures. Despite these promising reports,
ESIS is not widely integrated into pediatric DRE evaluation.
The overall objective is to improve methods of EZ identification in pediatric DRE
patients with complex EZs, thereby increasing the likelihood of surgical candidacy for
patients and ultimately improving surgical outcomes. In this protocol, investigators
hypothesize that electrical stimulation of induced seizures (ESIS) is an effective
adjunct for EZ delineation in children with DRE. To test this, the study will enroll n=86
patients with DRE undergoing sEEG evaluation aged 1-30 years. Based on the CCHMC epilepsy
surgery program throughput, it is anticipated that this will include approximately n=36
patients with TSC and n=50 without TSC, which will provide the opportunity to compare the
utility of this technique between patients with and without TSC. Patients will undergo
ESIS using published Cincinnati Children's Hospital Medical Center (CCHMC) parameters
with modifications. Gray and white matter contacts will be stimulated systematically.
Safety, tolerability, yield, validity and parameter space will be examined.