Abstracts

Rationale:
Drug-resistant epilepsy has a significant negative impact on quality of life and may be associated with life-threatening events. Neurosurgical procedures such as resection and laser ablation have proven effective in reducing seizure burden in patients with drug-resistant epilepsy. Removal or ablation of brain tissue can result in significant postoperative deficits if the epileptogenic focus is located in the eloquent cortex.  The responsive neurostimulation (RNS) device, Neuropace, is an FDA approved device for adjunctive treatment of focal seizures in adults 18 years and older. Evidence for the safety and efficacy of RNS devices in the pediatric population is limited. We describe the case of one patient at Rady Children’s Hospital San Diego, a 9-year-old female with a two-year history of drug-resistant epilepsy who underwent placement of a RNS device and, although seizure free, exhibited a decline in multiple neuropsychological scores compared to preoperative baseline.
Method:
A detailed review of the patient's diagnostic and treatment plan were discussed in multidisciplinary case conferences across multiple dates. The patient ultimately had implantation of a subdural grid over the left frontoparietal head region. Seizures were noted to originate from the primary motor cortex involving her right non-dominant hand. She was deemed a poor candidate for surgical resection or laser ablation due to the high chance of right hand weakness. A consensus decision was made to proceed with RNS device implantation. She underwent surgical placement of the Neuropace RNS device with two 4-contact electrode strips over the hand motor and premotor area. The RNS device was activated two months after device placement with initial settings of current 1mA, frequency  200Hz, pulse width 160µs, burst duration 100 msec, and charge density 0.5 µC/cm2.  Follow up neuropsychological testing was performed 1.5 years after device activation.
Results:
The patient tolerated the procedure well and has been seizure free since device implantation. Unfortunately, once the device was set to stimulation mode she began to develop somatic complaints. Initially, she complained of vertigo and lightheadedness prompting concerns for adverse effects of the RNS device. However, magnet deactivation of the system at home did not alleviate complaints. She later developed abdominal pain and episodes of shortness of breath at school. These somatic complaints increased and intensified to the point that she began exhibiting difficulty at school, leading mother to hold the patient from school for over a month. The patient had resolution of her somatic complaints one year after device placement.  Follow up neuropsychological evaluation revealed that, in addition to the preoperative deficits in fine motor skill and sustained attention, there were declines on measures of executive skill and quantitative reasoning. This decline may reflect a failure to make age-appropriate gains in skills, “growing into” deficits with age, resulting in social withdrawal and somatization.  The patient has been seizure free for two years and has discontinued 1 of 3 of her seizure medications, with plans for further medication reduction.
Conclusion:
RNS should be considered as a viable therapy in pediatric patients with drug-resistant epilepsy that are not amenable to resection or laser ablation. However, the interplay between RNS devices and normal childhood development and psychology warrants further investigation. Further, the age and developmental stage of candidates for RNS device placement should be a focus of discussion during preoperative evaluation. Ultimately, monitoring of behavioral and psychological outcomes in pediatric patients after RNS device implantation is warranted.
Funding:
:None