I have an implanted vagus nerve stimulator (VNS by
Cyberonics), which is normally used in cases of partial-onset epilepsy. In my case it was considered a possible alternative for "treatment-resistant depression". I believe it only benefits those patients with
dysautonomia, which is why there are equivocal results from studies concentrating on "depression". There have been a number of times when I had unexplained (vasovagal?) syncope (fainting).
It appears to shift the balance between the sympathetic and parasympathetic nervous systems, which helps to compensate for an anciendaze. This does not correct damage to the autonomic nervous system but may reduce symptoms which interfere with normal health. (If it makes a difference in your ability to sleep it can be life-saving.) Research indicates VNS reduces production of pro-inflammatory cytokines, which fits in with a number of models of ME/CFS as a neuroinflammatory disorder. The cause of the inflammation remains elusive.