I'm lucky enough not to need a VNS.
But I would think the best person to talk to is your Neurologist about things like what batteries to use in it.

Annie, I have had the VNS for years and it has helped me. My doctor who introduced me into having it done, spoke of a meeting I could go to to learn more about it, in which I went.
Everything you want to know, don't hesitate to ask your Dr. he/she should be good about telling you anything you want to know.

I have had a VNS for the past 4 years. The battery pack VNS unit I had first only lasted 3 years. I got the newer unit this last time and the battery pack is supposed to last longer. The one thing I can tell people is the more you swipe it/the higher the settings the sooner the battery pack will start to die. The surgery was not bad and they amp up the settings slowly and it has helped my seizures.These units do only work for certain kind of seizures though. Hope this helps someone.

I am sorry. I haven't had either treatments. So, I don't have an answer.

I believe all batteries have a problem with heat dependent on condition of batteries and unit using the battery. There are PDF files that help users determine how heat distributes and how to circumvent