Chronic pain: a neuroscientific understanding.

The neuroscientific understanding of chronic pain presented evolved through the integration of clinical, research and theoretical conceptualizations associated with chronic idiopathic orofacial pain after posing the following three questions: (1) What if chronic idiopathic orofacial pain was viewed from a neuroscientific perspective as part of a global syndrome rather than a site-specific anatomo-physiological perspective? (2) What if it was assumed that rather than serving no useful purpose chronic idiopathic orofacial pain served a useful purpose? (3) Would current knowledge be sufficient to explain chronic idiopathic orofacial pain? The understanding defines chronic pain as being a centrally perceived event expressing the continual or episodic persistence of a level of peripheral and/or central neural activity above the pain threshold of a sensitized nervous system that is sufficient to maintain the sensitization. This ongoing neural activity may be associated with or independent of the neural activity that initiated the sensitization. In effect the nervous system is "bruised" and the "bruising" is being maintained (prodded) by the total neural activity of the system irrespective of its origin; the normal protective healing function of the nervous system, pain, continues its warning when the activity of the system activates the switch that is the pain threshold. The common clinical history of initial trauma and ongoing stress suggests that chronic pain might be thought of as an expression of post-traumatic stress. Treatment based on the presented understanding would aim to reduce and maintain total neural activity below the pain threshold level and ideally down to where the sensitization can be reduced or even resolved by neuroplastic processes, the level rather than the origin of neural activity being relevant to the pain mitigation. A review of chronic pain in the light of this understanding will provide the opportunity to formulate, test and refine new and existing strategies for its prevention and treatment, thereby offering hope to the millions of sufferers worldwide.