Abstracts

Rationale: Vagus nerve stimulation (VNS) has been widely used for treatment-resistant epilepsy in both adults and children since its FDA approval in 1997. As far as external interference to device function is concerned, effects of heat and electromagnetic field of MRI scanners on VNS has been well documented and discussed. Other common external devices such as home appliances, cell phones etc. do not have effect on VNS function. Theoretically high energy devices such as transmitting antenna may affect the device and VNS manual advises to move at least 6 feet away from the source to avoid effects on the device. Lightning strike has much higher energy than any such devices and can potentially affect VNS or other implantable devices even from greater distance. We report a case of a patient who suffered malfunction of VNS and associated magnet after an unusual electric interference due to lightning strike near her house. Methods: Case analysis with PUBMED literature review was employed. Results: This case is of a 20 year-old woman with a history of traumatic brain injury in 2004 at the age of 10 years, which was followed by development of epilepsy with focal seizures starting in 2007. After multiple medication trials, the patient had a VNS implanted in 2009 for refractory epilepsy and has been on stable settings unchanged since 2011 with improvement in seizure frequency and severity and no adverse effects. Her current antiepileptic medications included lamotrigine 350 mg twice daily and phenytoin ER 230 mg daily. During a thunderstorm in 2014 about 5 years after VNS implantation, there was an intense lightning strike near her home, but the house was not thought to be struck by lightning. Following this storm, some home devices such as garage door opener, cell phone, and a TV remote control, stopped functioning. The patient's parents tried swiping the patient's magnet to test the VNS, and the patient did not have then normal sensation she has with magnet activation. Her VNS was interrogated, and the output and magnet current had been reset to 0.00 mA. One of the VNS magnets also had stopped working. The patient fortunately did not have any major seizures during this period, and the VNS appeared to function normally when reprogrammed. Conclusions: The high electromagnetic energy of lightning strike can cause VNS failure even at a significant distance. Only one similar case had been reported, where the device not only stopped working but was deemed inoperable after investigation. The iatrogenic and potentially avoidable electromagnetic interference notably from electrocautery and ablation procedures has been reported for several other implanted electrical devices, such as pacemakers and implantable loop recorders. Further reports and investigation of ways to avoid this interference should be taken into consideration while designing new models of VNS devices to make it safer and resistant to such events. This may help prevent unnecessary breakthrough seizures and surgeries to replace malfunctioning devices. Patients should also be made aware of the possibility for lightning storms to result in malfunction of the VNS.