Abstracts

Rationale: As many as 40% of patients with idiopathic generalized epilepsy (IGE) have poorly controlled seizures. Brain stimulation is an emerging surgical therapy that holds great promise for reducing seizure burden in patients with medically refractory IGE. Here, we present two-year outcomes for four patients with IGE implanted with the NeuroPace RNS System.

Methods: Four patients with pharmacoresistant epilepsy underwent bilateral implantation of the centromedian nucleus (CM). RNS was set to record intracranial electroencephalography (iEEG) without stimulation in order to characterize baseline thalamic electrophysiology. Electrophysiology data were extracted from the Patient Data Management System (PDMS) and analyzed using a custom-built platform (BRAINStim). Postoperative visualization of electrode locations was performed with Lead DBS and the Morel atlas of the thalamus. Seizure control assessments were reported in relation to the Engel outcome scale.

Results: Patient 1 presented as a 19-year-old female with an 8-year history of eyelid myoclonia with absences who experienced a >90% reduction in seizure frequency and periods of >48 h without seizures and achieved an Engel class IB outcome. Patient 2 presented as a 24-year-old male with a 13-year history of absence and generalized tonic-clonic seizures who experienced a reduction in seizure severity and frequency and achieved an Engel class IIA outcome. Patient 3 presented as a 23-year-old female with a 7-year history of juvenile myoclonic epilepsy with generalized tonic-clonic seizures and absences who experienced a reduction in seizure frequency of 75–89%, length of individual seizures, and duration of post-ictal state with a Engel class IIIA outcome. Patient 4 presented as a 33-year-old female with a 16-year history of generalized tonic-clonic seizures with a reduction in seizure frequency of 90–99% and an Engel class IC outcome.

Electrodes were implanted in the CM (10), posterior (Po–2), ventral posterior medial (VPM–4), anterior ventral posterior lateral (VPLa–1), posterior ventral posterior lateral (VPLp–4), posterior-dorsal ventral lateral (VLpd–2), posterior-ventral ventral lateral (VLpv–3), intralaminar (Li–), pulvinar anterior (PuA–1) regions of the thalamus, or in white matter (WM–5). Detection accuracy for all patients overall decreased over successive programming epochs from a mean of 96.5% to 88.3%. The greatest number of electrodes used to deliver stimulation were the CM (7/10) followed by the VLpd (2/2), VPLp (3/4) and VLpd (2/3). In all patients, stimulation varied from 0.2–2.0 mA and amplitude only increased over successive epochs. The raw percentage of iEEG recordings with stimulations delivered to electrographic seizures was 24.8% (Patient 1), 1.2% (Patient 2), 7.6% (Patient 3), and 8.8% (Patient 4).

Conclusions: Closed-loop stimulation of the CM region may provide significant improvement in seizure control and quality of life for patients with drug resistant IGE. Optimal detection and stimulation locations and parameters remain an active area of investigation for accelerating and fine-tuning clinical response.

Funding: Please list any funding that was received in support of this abstract.: N/A.