Wednesday, October 24, 2007
Now there is a novel title! A part of “Explain Pain” in the clinic is to give meaning to the patient’s symptoms. By providing meaning and explanation, the “threat value” of the symptom is usually reduced, thus reducing engagement of coping systems such as the sympathetic, immune, endocrine, motor and pain systems. One of the joys of reading clinical neuroscience is the discovery of explanation. Let me give you one example: Mirror pains – the once perplexing state where the same pain (area and nature) is experienced in the other limb has been shown to have an immune system basis (Milligan, Twining et al. 2003). In the past, I tried to make up explanations for patients, such as that it was new or different use of the limb, but for me (and surely the patient) it was always unconvincing. And imagine the patient’s distress and fear that their problem was now spreading and seemingly out of control. The research by Milligan’s group showed that if immune activating compounds are injected around rat sciatic nerve, ipsilateral allodynia can be observed. If more compound is injected, then the allodynia is bilateral. This response is rapidly reversed by glial metabolic inhibitors. Glia are one source of the proinflammatory cytokines such as Interleukin 1 &6 and TNF which appear to underpin the mirror pains. My narrative may be something along the lines of “mirror pains are quite common and we are now beginning to understand them. Your brain has calculated that due to all the circumstances around your injury (eg no explanations, failed treatment to date, work pressure etc etc) that you need a bit more sensitivity, a bit more protection, so it has done a really good job and made pain on both sides. Don’t worry when we can get you in control of this, your brain will realise that it doesn’t need to make so much pain………..” More calming therapeutic narratives in later blogs. Milligan, E. D., C. Twining, et al. (2003). "Spinal glia and proinflammatory cytokines mediate mirror-image neuropathic pain in rats." The Journal of Neuroscience 23: 1036-1040.