TNF and peripheral neuropathy: The production of anti-neuronal antibodies and the BBB breakdown driven by pro-inflammatory cytokines, such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-α produced in the small bowel, contribute to the development of peripheral neuropathy, headache, cognitive impairment, “brain fog”, epilepsy, psychiatric symptoms, or states of neurological low chronic inflammation [17].