Association between brain and low back pain.

Most chronic low back pain includes elements of nociceptive pain, neuropathic pain, and nonorganic pain. We conducted screening for nonorganic pain with use of the Brief Scale for Psychiatric Problems in Orthopaedic Patients (BS-POP), which is simple and can be used for multidimensional assessment. Research on pain areas using functional magnetic resonance imaging (fMRI) and positron emission tomography has shown that the dopamine system contributes to the pathology of chronic low back pain. Chronic low back pain patients show decreased activation of the anterior cingulate cortex, prefrontal cortex, and nucleus accumbens. Given that both the anterior cingulate cortex and prefrontal cortex belong to the descending inhibitory system, and that the nucleus accumbens, which is involved in the dopamine system, releases μ-opioids that act to relieve pain, decreased activation in these three brain regions may be related to decreased function of the descending inhibitory system. A pathological condition that can be explained at the molecular biological level clearly exists between chronic low back pain and psychosocial factors, and investigations of a pathological condition of chronic low back pain including brain function are needed.