Resection After Responsive Neurostimulation for Bilateral Mesial Temporal Epilepsy: Why Continuing Neurostimulation...

Prior research has suggested that select patients with refractory bilateral mesial temporal lobe epilepsy (MTLE) treated with responsive neurostimulation (RNS) may benefit from eventual resection of the more active side. However, there is little guidance regarding the role for continuing RNS therapy after unilateral resection. Our series aims to help define the utility of continued RNS therapy after resection and offer guiding principles for neurostimulation in this context.

Retrospective chart review was performed for patients who underwent RNS implant surgery for bilateral MTLE at our institution between the years 2015-2024.

Five patients with RNS treating bilateral hippocampi ultimately underwent selective mesial temporal lobe resection on the primary side. After resection, 4/5 became seizure-free immediately; patient 4 had a 70% seizure reduction, with reemergence of seizures on the less active side. After reprogramming RNS to increase total number of daily stimulations, patient 4 became seizure-free. All patients continued RNS therapy after resection with the ipsilateral electrode used for monitoring, while the contralateral electrode monitored and delivered stimulation. Two patients had transient interruptions of RNS stimulation after resection associated with seizure relapse, followed by return to seizure freedom once stimulation was restored.

This series suggests that (1) unilateral remission in patients with bilateral MTLE being treated with RNS may be stimulation dependent; thus, stimulation should continue after unilateral resection; (2) unilateral seizure remission may depend on a particular threshold of number of stimulations per day.