In a brazen act of lazy research, I have read the Wikipedia article on the blood-brain barrier. I promise to look further because this is actually pretty interesting.
The blood-brain barrier is what separates circulating blood from the fluid in the brain that comes from the central nervous system. Basically, it keeps the bad things out of brain fluid and lets in the good things. Mildly ironically, the good things include glucose and amino acids. The bad things are bacteria and viruses, which is a good thing because the blood-brain barrier also keeps out drugs that would fight any infection that gets through.
The most pertinent to fibromyalgia is that the blood-brain barrier is weakened during inflammation. In addition, oxidative stress (something that constantly comes up in reading about fibro), apparently also plays a role in weakening the blood-brain barrier. I don’t think that necessarily means that people with fibromyalgia (inflammatory fibromyalgia, if there is indeed two different types of fibromyalgia) are susceptible to brain infections or diseases as such. However, it does raise a question about sensitivity to glutamate.
Ingesting glutamate in food is not really a problem in terms of the blood-brain barrier, but weakening the blood-brain barrier with chronic inflammation could cause increases in glutamate levels which then works against magnesium as a block for NMDA (N-methyl-D-aspartate [remember asparate?]). I wonder if, when the barrier is weakened, a sensitivity to ingested glutamate is then created because it can more easily cross that barrier – this then leads to excitotoxicity. As always, I don’t know what I’m talking about, but it seems like that lays the groundwork for chronic pain/fibromyalgia.
I have found an article from 2014 discussing the the connection between blood-brain barrier permeability and fibromyalgia (Dos Santos et al, see library later) which talks about the cascading effect starting with inflammatory pain causing blood-brain barrier weakening, so this possible connection is not completely out in left field, so I need to keep looking at it.