Abstracts

Rationale: Responsive neurostimulation (RNS; NeuroPace) is currently in a pivotal clinical multi-center trial to assess its efficacy as an adjunctive treatment for medication-resistant partial-onset epilepsy. The RNS is a closed-looped strategy with the aim of suppressing the ictal onset. Specifically, focal stimulation is delivered directly in response to its automated detection. To our knowledge, its potential use to synchronize with closed-circuit video monitoring has not been reported. Methods: We report a 24 year old male (CH) with a history of bilaterally independent temporal lobe epileptic sources. MRI demonstrates a post-traumatic left lateral temporal encephalomalacia. Scalp video-EEG monitoring revealed a similar stereotypic semiology for both left and right temporal epileptic sources. CH was enrolled in the now closed RNS feasibility trial. Intracranial electrodes were placed at epileptic sources as identified by a presurgical evaluation. Subtracted ictal SPECT co-registered to MRI (SISCOM) and dipole source modeling were used to place a left subdural 4-contact lead near the antero-lateral temporal encephalomalacia. A 4-contact depth lead was situated in the white matter adjacent to the right anterior-to-mid hippocampal formation. Results: One of the typical seizures was reported by the patient while being monitored by a closed-circuit commercial webcam installed in a University thoroughfare (Fig 1). The semiology was consistent with a complex partial seizure. It was described as upper body waving while sitting. The patient denied recollecting an aura. We were able to associate the webcam timestamp with the electrocorticogram download from the RNS memory buffer (Fig 2). Fast rhythmical activity with increasing amplitude was recorded through the left subdural lead. Despite the delivery of stimulation therapy, the ictus evolved into a stereotypic electrographic seizure pattern. In addition, we observed electrographic propagation of the event to the right hippocampal formation. The RNS was useful for identifying the epileptic source of this particular clinical seizure as originating in the left laterotemporal region. Conclusions: The RNS is currently investigational as a treatment modality. However, this well documented case illustrates its potential use for diagnostic localization during real-world ambulatory monitoring.