Treatment of drug-resistant epilepsy in patients with periventricular nodular heterotopia using RNS® System: Efficacy and description of chronic electrophysiological recordings.

OBJECTIVES: Describe changes in clinical seizure frequency and electrophysiological data recorded in patients with medically-intractable seizures and periventricular nodular heterotopias (PVNH) treated with the RNS® System (NeuroPace, Inc., Mountain View, CA). METHODS: Clinical seizures from eight patients (mean follow-up of 10.1 years) were analyzed pre- and post-treatment. Chronic ambulatory electrocorticograms (ECoGs) recorded from PVNHs, hippocampus and neocortex were evaluated to identify the earliest electrographic seizure onset type, pattern of spread, and interictal characteristics. RESULTS: Mean reduction in disabling seizures was 85.7 % (n = 8); seven patients had >50% seizure reduction and two were seizure-free in the final year of analysis. Seizure rate showed a progressive reduction over the course of the study with the highest rate of improvement in the first two to three years after implantation. Four of seven patients with one PVNH lead and a second lead in the hippocampus or neocortex had some electrographic seizures first recorded at either lead location, suggesting two foci or seizure propagation patterns. Low voltage fast type activity was the prominent seizure onset pattern. Interictal ECoG power was lower in PVNH than hippocampus. CONCLUSIONS: RNS® System treatment substantially reduced clinical seizure frequency in patients with PVNH. Analysis of ictal ECoG records suggests PVNH may be involved in seizure generation. SIGNIFICANCE: Chronic ECoG recordings suggest PVNH tissue can actively participate in epileptogenic networks. Direct brain-responsive neurostimulation is a safe and effective treatment option in such patients, progressively reducing seizure rate over a period of years.

Brain-responsive neurostimulation in patients with medically intractable seizures arising from eloquent and other neocortical areas.

OBJECTIVE: Evaluate the seizure-reduction response and safety of brain-responsive stimulation in adults with medically intractable partial-onset seizures of neocortical origin. METHODS: Patients with partial seizures of neocortical origin were identified from prospective clinical trials of a brain-responsive neurostimulator (RNS System, NeuroPace). The seizure reduction over years 2-6 postimplantation was calculated by assessing the seizure frequency compared to a preimplantation baseline. Safety was assessed based on reported adverse events. Additional analyses considered safety and seizure reduction according to lobe and functional area (e.g., eloquent cortex) of seizure onset. RESULTS: There were 126 patients with seizures of neocortical onset. The average follow-up was 6.1 implant years. The median percent seizure reduction was 70% in patients with frontal and parietal seizure onsets, 58% in those with temporal neocortical onsets, and 51% in those with multilobar onsets (last observation carried forward [LOCF] analysis). Twenty-six percent of patients experienced at least one seizure-free period of 6 months or longer and 14% experienced at least one seizure-free period of 1 year or longer. Patients with lesions on magnetic resonance imaging (MRI; 77% reduction, LOCF) and those with normal MRI findings (45% reduction, LOCF) benefitted, although the treatment response was more robust in patients with an MRI lesion (p = 0.02, generalized estimating equation [GEE]). There were no differences in the seizure reduction in patients with and without prior epilepsy surgery or vagus nerve stimulation. Stimulation parameters used for treatment did not cause acute or chronic neurologic deficits, even in eloquent cortical areas. The rates of infection (0.017 per patient implant year) and perioperative hemorrhage (0.8%) were not greater than with other neurostimulation devices. SIGNIFICANCE: Brain-responsive stimulation represents a safe and effective treatment option for patients with medically intractable epilepsy, including adults with seizures of neocortical onset, and those with onsets from eloquent cortex.