Department of Neurology

Questions about using the magnet trigger for vagus nerve stimulation in developmentally disabled persons

Q: My sister is 21 years old and she has brain damage and has a lot of seizures. Her doctor suggested the vagus nerve stimulator. I would like to know if you have to use the stimulator before a seizure or whether it can work after the seizure has begun because she has to much brain damage to do it herself.

Thank you for your time,


Q: I'm writing with a question regarding the "vagus nerve stimulator." I hope you will be able to give me some information or maybe lead me in the right direction. I am the Administrator for 4 group homes for adults with developmentally disabilities. We are considering admitting a young man who has the implant and is moderatley mentally retarted. He does not use it independenlty, and is not able to determine when a seizure is coming on or what his aura is, if any. His mother has always used the magnet after the seizure has begun, it she gets to him in time. My question is, is using the magnet after it's already started doing any good? Should it be used before the seizure starts or does it still help to use it at this point?

Again, thanks!


A: The vagus nerve stimulator has two modes. It is programmed to go off automatically at preset time intervals, usually every 5 minutes. The stimulator can also be triggered manually, using a magnet. Many patients cannot use the magnet, either because they don't have an aura, or because it is too brief for them to use the magnet before they lose consciousness. As it turns out, most patients do not use the magnet regularly, but nonetheless have a good effect form the device. From both clinical experience and some laboratory research at our institution, it is pretty well established that vagus nerve stimulation exerts a antiseizure effect that persists after the end of stimulation. Thus, it appears to be effective even if it is not turned on when a seizure starts. Thus, inability to use the magnet trigger would not necessary prevent a patient from receiving this therapy.

To answer the second question, some persons report that if they use the magnet to trigger a pulse at the start of their seizure, they can abort or reduce the duration of the seizure. This has not been systematically examined in humans, but in animals, a pulse of vagal stimulation does appear to shorten the seizure, but only if given close to the start of the seizure. We currently recommend that if the magnet trigger is used, it should be used as soon as possible after the start of the seizure, preferrably during the aura if there is one. It may be worthwhile to try it even if the person is already in middle of the seizure. Whether it helps or not is probably dependent on the individual and must be judged in hindsight.

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