Abstracts

Rationale: Responsive Neurostimulation (RNS) and Vagus Nerve Stimulation (VNS) are two nonpharmacological therapies approved for treatment of intractable epilepsy. There are significant differences between these two neuromodulation systems and their level of efficacy varies across different types of epilepsy. To date, there are no reports in the literature describing patients who have both devices working simultaneously.  We present two such cases, illustrating the clinical benefit in combining these techniques in patients with intractable epilepsy and demonstrating synergistic neuromodulation. Methods: Case reports Results: Case 1Case of a 52-year-old right-handed man with moderate intellectual disability and history of bilateral mesial temporal sclerosis as a result of viral encephalitis at 10 months of age. He experienced debilitating focal non-motor seizures with impaired awareness and focal motor seizures with secondary generalization. Seizure control remained poor despite optimal treatment with several antiepileptic medications and VNS in 2004. The decision to place a RNS with electrodes targeted in bilateral mesial temporal regions was based on surgical evaluation findings: left temporal hypometabolism, L>R mesial temporal sclerosis, neuropsychological testing, and independent ictal and interictal findings from bilateral mesial temporal structures. RNS electrocorticography (ECoG) recordings showed seizures originating from the left mesial temporal region. However, almost a year into treatment with RNS, ECoG recordings began to capture right mesial temporal seizures. The appearance of right temporal seizures coincided with VNS battery failure. After the battery was replaced, right-sided seizures were no longer captured. With the VNS being used to treat the patient’s right temporal seizures, the RNS settings were adjusted to focused left temporal stimulation parameters.Case 2Case of a 29-year-old right-handed man who developed seizures and severe memory disturbance related to hypoxic brain injury in the context of a drug-overdose at age 17. Drug-resistant non-motor focal impaired awareness seizures occurred every 2 days. MRI showed small hippocampi, left smaller than right. Invasive monitoring in 2008 captured independent bi-temporal seizures. VNS was implanted and reduced seizure count, but ongoing frequent seizures led to significant memory decline. This forced him out of school and employment, and back into his parents’ home. RNS with two bi-hippocampal leads was implanted in 2015 and lowered seizures to once monthly. Three months after RNS placement, VNS was turned off because of malfunction, and within 2 months the seizure frequency increased to daily. Conclusions: These cases illustrate that despite the different mechanisms of action of these two neurostimulation devices, they can work synergistically to improve a patient’s seizure frequency. The combination of the neuromodulation techniques allows us to treat multiple seizure foci and a broader epileptogenic network to decrease seizure burden in patients with refractory epilepsy. Funding: Not applicable