Living with Vagus Nerve Stimulation

My son has been dealing with complex partial siezures [seizures] for over ten years. He has the VNS implanted and it did help, especially during a siezure [seizure]. He has now developed, what has been described as a focal siezure, so now he suffers from both the convulsive and the focal siezure. The focal siezure, which is a severe twitching of his right arm, doesn’t stop and the doctors are unable to even see this siezure during an EEG. I’m at my wits end with the system, when there doesn’t appear to be any help. I am also wondering if this focal siezure is being triggered by the VNS, but the doctors didn’t want to shut it down to test it, while we were there. He has a separation in his brain, on the front left temporal lobe, due to a trauma of falling off a ride at the amusement park in Santa Cruz. I need suggestions from anyone that may have ideas, seeing how the doctors are running out of ideas. Feeling helpless in Ca.