Treatment of medically refractory seizures with responsive neurostimulation: 2 pediatric cases

Abstract

The responsive neurostimulation (RNS) system, an adjunctive treatment for pharmacoresistant partial-onset seizures with 1 or 2 foci, has been available to patients aged 18 years or older since the device's FDA approval in 2013. Herein, the authors describe their off-label application of this technology in 2 pediatric patients and the consequent therapeutic benefit without surgical complications or treatment side effects. A 14-year-old nonambulatory, nonverbal male with severe developmental delay was considered for RNS therapy for medically and surgically refractory epilepsy with bilateral seizure onsets in the setting of a normal radiological examination and a known neuropathological diagnosis of type I cortical dysplasia. The RNS system was implanted with strip electrodes placed on the left lateral frontal and right lateral temporal neocortex. At 19 months' follow-up, cortical stimulation resulted in sustained reduction in both seizure frequency-3 seizures per day down from 15 to 30 per day-and seizure severity. The patient subsequently underwent a trial of corticothalamic stimulation with a right temporal cortical strip and a left thalamic depth electrode, which resulted in a further 50% reduction in seizure frequency. In a second case, a 9-year-old right-handed female with radiological evidence of a small watershed infarct on the left and medically refractory seizures was referred for presurgical evaluation. Invasive monitoring revealed an unresectable seizure focus in the eloquent cortex of the left posterior frontal and parietal lobes. The RNS device was implanted with cortical leads placed at the putative seizure focus. At 21 months after surgery, the patient had been seizure free for 4 months, following a 17-month period in which the seizure frequency had decreased from 12 per month to 2 per month, with associated functional and behavioral improvement. The authors' results suggest that RNS may be a palliative option for children with intractable seizures whose condition warrants off-label use of the surgical device. The improved therapeutic effect noted with time and sustained RNS treatment points to a possible neuromodulatory effect.

Keywords: AED = antiepileptic drug; DBS = deep brain stimulation; ECoG = electrocorticography; EEG = electroencephalography; FCD = focal cortical dysplasia; MRE = medically refractory epilepsy; MST = multiple subpial transection; RNS; RNS = responsive neurostimulation; VNS = vagus nerve stimulation; children; epilepsy; neuromodulation; responsive neurostimulation; surgical failure.