This is a touchy subject, but the gist of it is that nearly all evidence points to post-Lyme complications being due to something other than ongoing Lyme infection. However, there are a lot of alternative medicine doctors who try to treat post-Lyme complications as ongoing infections that they claim are too hidden to be measured or detected. They want to treat the "hidden infection" with extremely long courses of very powerful (and expensive) antibiotics.
The problem with this theory is that when studied under double-blind conditions, the post-Lyme patients who receive high dose antibiotics don't actually do much better than those who receive placebo. Similar numbers of patients in both placebo and antibiotic groups have recoveries, but the antibiotic cohort has higher rates of adverse effects. Any time you have evidence like this, insurance companies will refuse to cover these treatments.
It's a touchy subject because post-Lyme symptoms are very real, but the cause of those symptoms isn't really understood. Patients who are desperate for answers are drawn to the high-dose, long-term antibiotic treatments because it gives a convenient explanation and a convenient treatment option, but the real-world results don't really support it. There are a few researchers out there who are still trying to prove otherwise, so it's possible that we'll get some different information later.
Sadly, there isn't much in the way of treatment knowledge for how to actually deal with post-Lyme complications, other than going for large batteries of neurological and immunological testing and hoping that something turns up. Beyond that it's largely palliative care and rest while the patient hopefully gradually recovers.