Mechanisms of chronic pain

Abstract

This review explains the following : First, it demonstrates that functional impairment of the prefrontal cortex leads to chronic pain due to improper functioning of the descending pain modulatory system. In addition, patients with chronic pain often develop “learned–nonuse,” a condition in which affected limbs are not used because of misinterpretation (distorted cognition) that movements cause pain. When learned–nonuse occurs, cerebral cortical areas associated with the execution of movement and sensation are reduced in size, which leads to functional impairments associated with these areas. If nonuse of the affected limbs is prolonged, the self–perception of the body is decreased as in neglect–like symptoms, and this decrease in cognitive ability may result in chronic pain or pain exacerbation. Neglect–like symptoms associated with the development of chronic pain is caused by the collapse in the perception–movement loop, particularly by the disturbed mechanism of the comparator model. The comparator model is involved in the embodied brain system. In the end, this review explains the hypothesis for the mechanism of how functional disturbances can occur in the embodied–brain systems of patients with chronic pain at all levels, from sensorimotor representation to propositional representation and meta–representations.