Phenotyping central nervous system circuitry in chronic pain using functional MRI: considerations and potential implications in the clinic.

Functional MRI (fMRI) has provided new insights into brain mechanisms in chronic pain. However, unlike acute pain measures in healthy volunteers, there are additional concerns relating to mapping brain circuits in these patients. These include the ability to measure evoked versus spontaneous pain, background conditions such as medications, or comorbid diseases such as depression, anxiety, or addiction. Nevertheless, our understanding of the centralization of pain with attendant changes in sensory, emotional, and autonomic function is being more clearly realized and has significant implications for defining the disease state and therapeutic interventions. It is possible that fMRI may become clinically useful.