Responsive Neurostimulation Targeting the Anterior, Centromedian and Pulvinar Thalamic Nuclei and the Detection of Electrographic Seizures in Pediatric and Young Adult Patients

Abstract

BackgroundResponsive neurostimulation (RNS System) has been utilized as a treatment for intractable epilepsy. The RNS System delivers stimulation in response to detected abnormal activity, via leads covering the seizure foci, in response to detections of predefined epileptiform activity with the goal of decreasing seizure frequency and severity. While thalamic leads are often implanted in combination with cortical strip leads, implantation and stimulation with bilateral thalamic leads alone is less common, and the ability to detect electrographic seizures using RNS System thalamic leads is uncertain.ObjectiveThe present study retrospectively evaluated fourteen patients with RNS System depth leads implanted in the thalamus, with or without concomitant implantation of cortical strip leads, to determine the ability to detect electrographic seizures in the thalamus. Detailed patient presentations and lead trajectories were reviewed alongside electroencephalographic (ECoG) analyses.ResultsAnterior nucleus thalamic (ANT) leads, whether bilateral or unilateral and combined with a cortical strip lead, successfully detected and terminated epileptiform activity, as demonstrated by Cases 2 and 3. Similarly, bilateral centromedian thalamic (CMT) leads or a combination of one centromedian thalamic alongside a cortical strip lead also demonstrated the ability to detect electrographic seizures as seen in Cases 6 and 9. Bilateral pulvinar leads likewise produced reliable seizure detection in Patient 14. Detections of electrographic seizures in thalamic nuclei did not appear to be affected by whether the patient was pediatric or adult at the time of RNS System implantation. Sole thalamic leads paralleled the combination of thalamic and cortical strip leads in terms of preventing the propagation of electrographic seizures.ConclusionThalamic nuclei present a promising target for detection and stimulation via the RNS System for seizures with multifocal or generalized onsets. These areas provide a modifiable, reversible therapeutic option for patients who are not candidates for surgical resection or ablation.

Responsive Thalamic Neurostimulation: A Systematic Review of a Promising Approach for Refractory Epilepsy

“…After removal of duplicates, 109 references underwent title and abstract screening resulting in the identification of 7 publications which met the inclusion criteria ( Osorio et al, 2005 ; Herlopian et al, 2019 ; Burdette et al, 2020 , 2021 ; Kokkinos et al, 2020 ; Welch et al, 2021 ; Beaudreault et al, 2022 ). A supplemental search of the reference lists and articles which cited these 7 publications was performed as well, yielding 3 additional publications ( Kokoszka et al, 2018 ; Elder et al, 2019 ; Kwon et al, 2020 ; Figure 1 , PRISMA Diagram).…”

“…At most recent follow up, 15 subjects were receiving stimulation in the ANT (7 unilateral and 8 bilateral nuclei), 11 in the CMT (2 unilateral and 9 bilateral) and three subjects in the PVN (2 unilateral and 1 bilateral). In addition, Beaudreault et al (2022) included two subjects in their 14-patient case series for whom follow-up data was not available; the other 12 subjects were included in this analysis.…”

“…The authors reported a 90–95% seizure reduction by 24 months and no adverse reactions to corticothalamic RNS. Finally, a large case series was recently published by Beaudreault et al (2022) which included six subjects with active leads implanted in the ANT. The authors report successful seizure detection and stimulation using the same ANT leads.…”

“…This case further highlights the efficacy of thalamic RNS in inducing remission of absence seizures. In addition, the recent review by Beaudreault et al (2022) includes six subjects with a range of response rates to RNS treatment targeting the CMT.…”

“…It is also challenging to make deductions from these studies regarding the effects of thalamic responsive stimulation on neurocognitive wellbeing, as only 1 out of 10 publications included formal neurocognitive testing at follow-up ( Burdette et al, 2021 ). Furthermore, whereas larger studies utilize responsive stimulation for several years before assessing the impact on seizure frequency, ( Ryvlin and Jehi, 2022 ) follow-up data for 12/29 of the subjects described in this review was obtained within 12 months from starting thalamic stimulation ( Osorio et al, 2005 ; Kokoszka et al, 2018 ; Burdette et al, 2020 , 2021 ; Kwon et al, 2020 ; Welch et al, 2021 ; Beaudreault et al, 2022 ). Finally, although seizure frequency was a primary outcome in all 10 studies, the RNS system cannot record for extended periods of time and does not track all data relating to seizure frequency ( Thomas and Jobst, 2015 ).…”