Reduced VNS settings paradoxically decreases seizure burden in a patient following resolution of sleep disordered breathing

Vagus nerve stimulation (VNS) can be a highly effective treatment option for patients with drug resistant epilepsy. Notably, VNS has demonstrated side effects including a unique form of sleep disordered breathing known as vagus nerve stimulator associated sleep disordered breathing (VaS). However, the ways in which VaS interacts with seizure frequency is unknown. We report a case of a 28-year-old woman who presented to our department with complaints of worsening sleep quality 3 years following VNS implantation. Upon polysomnographic (PSG) evaluation, it was discovered that she suffered from VaS. The patient's VNS output current was then down titrated during a subsequent PSG resulting in resolution of her VaS. Interestingly, despite downward titration of her nighttime VNS output current, the patient demonstrated a prolonged seizure free period, highlighting the complex interactions between VNS, VaS and seizure frequency. In cases where patients present with both epilepsy and VaS, physicians should be aware of this complex relationship. Further, this case highlights that down titration of VNS settings may result in not just improvement in VaS but may also result in improvement in seizure frequency.