Functional MRI and pain.

PURPOSE OF REVIEW: This article reviews the current state of knowledge in functional MRI (fMRI) research related to pain with primary focus on clinical studies.

RECENT FINDINGS: With fMRI, the subjective effects of pain (sensory, affect, emotion, and motor components) can be objectively imaged. Although the conventional fMRI technique has been the isolation of regions in the brain transmitting and modulating pain, functional connectivity measurement can identify functionally linked regions associated with pain processing. The primary and secondary somatosensory cortex (S1 and S2), anterior cingulate cortex (ACC), and insula are the four regions (part of pain matrix) consistently activated in pain states. Functional connectivity between the prefrontal cortex (PFC), ACC, and insula correlates well with clinical pain measures. The dorsal medial PFC to insula connectivity can identify patients prone to persistent back pain. Default mode network (DMN) to insula connectivity is associated with spontaneous pain in fibromyalgia patients. In addition, the DMN encompasses the PFC. Techniques for fMRI analysis, templates, and standards for identifying the functional networks in the brain are evolving continuously. The activation pattern with analgesic agents seems to be specific to the class of drugs.

SUMMARY: As we learn more about fMRI related to pain, functional connectivity patterns could emerge as biomarkers for specific pain conditions.