Anterior Nucleus and Pulvinar Thalamic Four-lead Deep Brain Stimulation in Addition to Cortical Responsive Neurostimulation in a Patient with Medically Refractory Epilepsy

Introduction: Medically and surgically refractory epilepsy presents significant challenges for treatment. This is likely the result of complex network pathologies, requiring multi-modal approaches to achieve seizure control. Thalamic Deep brain stimulation (DBS) is an FDA-approved neuromodulation modality for refractory epilepsy, in addition to responsive neurostimulation (RNS) and vagus nerve stimulation. Current DBS therapies have been limited to stimulating single thalamic targets, with the anterior nucleus of the thalamus (ANT) being a major site of therapy. The Pulvinar thalamus (Pul) has been a target of interest for posterior quadrant seizure control for patients refractory to ANT DBS stimulation.

Methods: The ANT and Pul were simultaneously implanted using four 8-contact leads (directional for ANT and standard ring electrodes for Pul) placed through 2 burr-holes, connected to a 32-channel pulse generator. The patient later developed a non-infectious seroma and erythema which led to removal and reimplantation. Subjective seizure logs were maintained throughout this period.

Results: After two months of 4-lead ANT + Pul DBS, there was a reported seizure reduction from 12-14 to 2-3 seizures/day (75-85% reduction). Interestingly, RNS ECoG demonstrated an initial increase in total event (159 to 357, p< 0.01) and long episode detection (0 to 16, p< 0.01) followed by a decrease. These trends strongly reversed after DBS IPG removal and immediately re-established after reimplantation (changes in daily seizures–12 to 2, total RNS event detection–172 to 206, p=0.02, and long episodes–0 to 39, p< 0.01). Tractography with lead reconstruction revealed anatomical connections between the 32-channel system and the RNS, perhaps suggesting the RNS leads were detecting stimulation effects of DBS.

Conclusion : We present a case report demonstrating the feasibility of a 32-channel multi-nuclei thalamic DBS strategy in addition to simultaneous cortical RNS for treating medically and surgically refractory epilepsy. This approach warrants further investigation as a therapeutic option for refractory epilepsy.