Abstracts

Rationale: Focal motor status epilepticus involving the primary motor cortex includes epilepsia partialis continua (EPC), characterized by prolonged, focal myoclonic activity that can persist for years. Pediatric EPC is associated with significant neurological consequences in 65% and lethal outcomes in 16%. The responsive neurostimulation system (RNS) is a closed loop neurostimulation device FDA-approved to treat chronic multifocal epilepsy in adults. Typical use of the RNS involves months or years of outpatient parameter adjustment for optimal seizure control.


Methods: We present a case of successful treatment of super-refractory focal motor status epilepticus in a child using combined limited focal resection and acute RNS implantation and treatment.


Results: Our patient is a 6-year-old left-handed female with a complex history of diffuse left hemispheric polymicrogyria and pachygyria, mild right hemiparesis, global developmental delay, near-continuous left frontopolar epileptiform discharges during sleep, and drug refractory daily brief left central focal motor seizures. While on vacation, the patient developed continuous right thumb twitching that escalated to include right face and arm jerking refractory to escalating medication treatments including benzodiazepine, levetiracetam, fosphenytoin, lacosamide, topiramate, phenobarbital, midazolam and propofol. Hemispherotomy was considered. She was transferred to our institution on hospital day 19, where video EEG demonstrated 2-5 Hz left frontal discharges time-locked to her myoclonic jerks. Ictal PET scan demonstrated hypermetabolism in the left frontal region. The patient underwent resection of the frontopolar ictal focus guided by intra-operative electrocorticography. An RNS was implanted with 2 depth electrodes targeting presumed superior and inferior motor cortex identified by intraoperative sensorimotor mapping. After ~24 hours seizure-free, the patient again developed EPC on POD1. RNS recordings revealed abundant epileptic spikes in the contacts over presumed primary motor cortex (channels 1 and 3). Neurostimulation at these contacts resulted in worsened myoclonus. Lead-to-lead stimulation over the contacts estimated to be immediately anterior to the primary motor cortex (channels 2 and 4) was tolerated and initiated on POD1. On POD 24, when treatment reached an estimated charge density of 4.1 mC/cm² (4 mA, 333.3 Hz, 160 ms pulse width, 200ms burst duration), the EPC stopped. The patient successfully tapered off multiple antiseizure medications, returned to baseline cognitive and motor function, and remained clinically seizure free over the subsequent 14 months with only occasional epileptiform activity observed on the RNS recordings.


Conclusions: This case demonstrates the potential role of neuromodulation to achieve seizure control in the acute setting in children. Use of this minimally invasive surgical treatment option avoids the functional morbidities that would result from alternate, destructive options. Compared to the outpatient setting, acute management with RNS may require rapid adjustments and higher currents.


Funding: NA