Traumatic Brain Injury causes gut permeability, which helps explain why TBI patients are at a higher risk of blood infections post injury.
“Researchers have known for years that TBI has significant effects on the gastrointestinal tract, but until now, scientists have not recognized that brain trauma can make the colon more permeable, potentially allowing allow harmful microbes to migrate from the intestine to other areas of the body, causing infection.. People are 12 times more likely to die from blood poisoning after TBI, which is often caused by bacteria, and 2.5 times more likely to die of a digestive system problem, compared with those without such injury.”
The ties between the brain and the second brain are remarkable. There is a direct and distinct pathway for the two to communicate. https://www.scientificamerican.com/article/gut-second-brain/
The gut permeability piece is interesting and in line with a lot of similarly manifested autoimmune conditions that result from eating offending foods. Most of these foods are endogenous plant derived pesticides like lectins, gluten, oxalates, etc. These chemicals irritate and inflame the walls of the gut, allowing larger food particles to slip through the tight junctions of the gut lining, which the body then mistakes for invaders and mounts an immune response. This chronic ramping of immune response can eventually lead to seemingly unrelated conditions like hasimotos thyroiditis, rheumatism, lupus, inflammatory bowel disease, skin conditions, etc.
So it’s not surprising that if TBI causes gut permeability, we would see similar ailments in those with TBI, and in the immediate acute aftermath of a TBI we’d see actual microbes getting into the blood.