Abstracts

Rationale: Epilepsy affects up to 80% of patients with Tuberous Sclerosis Complex (TSC).  Most seizures are focal, arising from a single tuber. Current surgical options for patients with TSC include tuber resection, corpus callostomy, VNS, and laser ablation.  The NeuroPace RNS System provides an adjunctive therapy in reducing the frequency of partial onset seizures in adults with medically refractory, focal epilepsy. The system is designed to continuously monitor brain activity, detect abnormal activity and respond by delivering imperceptible levels of electrical stimulation. We will discuss our center’s experience in evaluation and treatment of a patient with TSC following implantation of the RNS System.  Methods: CA is a 37 year old woman with TSC and seizures beginning at age 8.  History is negative for infantile spasms or intellectual disability.  Seizures as a child were described by prodrome of anxiety with progression to bilateral tonic clonic movements, with last tonic clonic seizure in 2010 following addition of Carbamazepine.  Habitual seizures are characterized by anxiety, rising sensation progressing to impaired expressive language with intact comprehension with apparent preserved awareness.  Progression of seizures results in impaired awareness, loss of postural tone and amnesia. Following presurgical evaluation, the patient underwent implantation of bilateral subdural electrodes for monitoring to evaluate feasibility of resection of the seizure focus or RNS System placement.  Due to the focal onset in left mesial temporal (MT) lobe, risk for of loss of mnestic function, and complex clinical presentation in case of TSC, this patient was not a good candidate for MT lobe resection. The patient elected to proceed with RNS System placement concurrently with grid and strip removal.  Two 4-contact cortical leads were placed in similar orientation to the anterior and middle subtemporal strips that were placed for intracranial monitoring.  Based on interictal EEG, two inactive cortical leads were placed over the lateral neocortex consistent with region adjacent to the dominant tuber. Results: CA reported 19 seizures in 96 days, 1.5 per week at her 9 month visit.  Baseline seizure frequency was 2 to 4 seizures per week.  In the last six weeks the patient reported 4 seizures, including a two week seizure free interval.  Subjectively the patient feels clinically seizures are milder, shorter in duration with shorter post ictal period.  The following graphs are daily detected electrographic abnormalities recorded by her neurostimulator. “Long episodes” (prolonged detections) are a good representation of her electrographic seizures.  Conclusions: The RNS System provides a safe and effective surgical alternative for patients with TSC. Remission rates for tuber resection is estimated at 57% depending on clinical, imaging and EEG data.  Epilepsy is often early onset, with may lead to damage of MT structures and “dual pathology”. The benefit of tuber resection must clearly outweigh the risks of due to high remission rate.  The RNS System provides no permanent risk for loss of mnestic function or damage to eloquent cortex. Cognitive outcomes data demonstrate gains in cognitive domains such a naming and verbal memory.RNS provides the flexibility to adjust detection and therapy settings.  The active cortical leads may be exchanged based on clinical observation and EcOG data. Therapy settings and strategies are adjusted based on patient response.  Cortical strips may deliver therapy to “encapsulate” the dominant tuber or alternatively between the cortical strip lead electrodes and the neurostimulator to stimulate a broader field of neocortex.    Funding: None