An inflammatory reflex develops following cell damage or an infectious inflammation (virus, bacteria, toxin). This results in the release of cytokines and inflammatory mediators. These inflammatory mediators cause a sickness syndrome- the fever, anorexia, fatigue, and withdrawal from activity that we all feel when we come down with the flu. People with other inflammatory conditions can feel the same sickness syndrome. People who suffer from conditions as varied as irritable bowel syndrome and gulf war syndrome often report similar symptoms which are part of this inflammatory response to their condition.
It is felt that much of this inflammation is mediated both afferently and efferently via the vagus nerve. The vagus nerve is the 10th cranial nerve. It is responsible for a number of actions in the body from coordination of breathing, speech, sweating and regulating heart beat to aiding in digestion to name a few. The principal neurotransmitter involved is Acetylcholine. [Thayer JF, Cleve Clin J Med. 2009 Apr;76 Suppl 2:S23-6. doi: 10.3949/ccjm.76.s2.05. Review.]
The vagus nerve is responsible for turning off inflammation in inflammatory cells in spleen, liver and periphery. There is a setpoint for triggering this inflammatory cascade. Individuals who are susceptible have poor Vagal tone-evidenced by reduced heart rate variability. In fact, you can check your heart rate variability by feeling your pulse and seeing how it changes when you inhale and take a deep breath and when you exhale fully. Try it. Feel the pulse at your wrist just below your thumb and note how your heart rate changes with deep breathing. High vagal tone is felt to indicate that there is little central inflammation. Low vagal tone is just the opposite. If your heart rate varies from beat to beat with breathing, you have good vagal tone and probably don’t have much systemic inflammation. If your heart rate doesn’t vary much, the opposite may be true. Since it is known that the vagus is the nerve that most frequently activated in central inflammation, this is a good test for whether your are suffering from, or susceptible to chronic inflammation and central sensitization.
With effective treatment, Vagal tone can be restored. Meditation and exercise are two activities proven to improve vagal tone. Not surprisingly, these are also known to improve the symptoms associated with conditions of chronic inflammation and central sensitization ranging from Fibromyalgia to Chronic Fatigue syndrome to Gulf War Syndrome and TMJ. It is important to include exercise and psychological techniques for managing pain such as meditation and cognitive behavioral therapy in your pain management program.