Authors :
Presenting Author: Harsh Shah, MD – VCU
Shawn D'Souza, MD – VCU
Satya Paruchuri, BS – VCU
Jan Hachmann, MD – Mayo Clinic - Florida
Christine Baca, MD – VCU
Sandra Dewar, PhD, RN – VCU
Jennifer Haynes, MD – VCU
Kenichiro Ono, MD – VCU
Kathryn Holloway, MD – VCU
Paul Koch, MD – VCU
Rationale:
Temporal lobe epilepsy (TLE) with bilateral seizure foci is unamenable to surgical resection. Closed-loop responsive neurostimulation (RNS) of bilateral temporal lobes and open-loop deep brain stimulation (DBS) of the anterior thalamic nucleus (ANT) are both approved neuromodulation treatments for such patients. Seminal studies for these treatment modalities demonstrated 18.4% of patients being seizure free with RNS1 and 16% of patients being seizure free with DBS2. Our institutional experience with these strategies has found a higher-than-expected rate of seizure freedom amongst patients treated with open-loop thalamic DBS. Given this, we sought to compare the two treatment strategies and identify factors associated with seizure freedom.
Methods:
Retrospective review of patients treated with closed-loop responsive stimulation with bi-hippocampal RNS and open-loop stimulation of bilateral ANT with DBS from 2014-2023 was performed. Chart review was performed to extract demographic and clinical variables, with postoperative seizure frequency determined by patients’ treating epileptologists. Pre-operative and post-operative images were co-registered, lead localization was performed, and volume of tissue activated (VTA) models were generated using patient-specific stimulation parameters using LeadDBS. To compare between the open (DBS) & closed (RNS)-loop cohorts, only patient-reported clinical seizures are compared with 6 months minimum follow-up.
Results:
We identified 10 patients treated with bilateral open-loop ANT stimulation (DBS), of which 6 have bitemporal seizure foci; median follow-up was 25.9 months and 4/6 (67%) patients with bitemporal epilepsy achieved seizure freedom (median duration of seizure freedom 22.5 months). We identified 23 patients (14 female) with closed-loop bi-hippocampal stimulation (RNS) of which 21 patients have bitemporal seizure foci; median follow-up was 56.9 months and 5/21 (24%) patients with bitemporal epilepsy achieved seizure freedom (median duration of seizure freedom 12 months). Detailed demographic and clinical variables along with seizure outcome data are provided in table 1. VTA analysis of ANT DBS patients demonstrates a Sweetspot intersecting with anterior aspect of the ANT (Figure 1), corroborating published literature. VTA analysis of RNS patients demonstrates a Sweetspot residing in hippocampal body and head (Figure 2), with no involvement of hippocampal tail or amygdala.Conclusions:
In our small cohort open-loop stimulation with bilateral anterior thalamic DBS resulted in higher rates of seizure freedom compared to closed-loop stimulation with bi-hippocampal RNS in patients with bitemporal epilepsy. Higher-than-published rate of seizure freedom (67%) amongst our DBS cohort is associated with VTA stimulation of the anterior aspect of the ANT while improved seizure outcomes with hippocampal RNS is associated with VTA stimulation of hippocampal head and body. Analysis of presurgical factors & structural connectivity that may explain this outcome are underway. Further generalization of our results will require a larger sample size. Funding: None