[Neuroimaging findings of central nervous system dysfunction in neuropathic pain]

The central mechanism of pain is influenced by multiple factors including the quality of stimulation, cognition, psychological status, environment, and genetics. The region of the brain modulated by painful sensation, taken together, are termed as "pain matrix," composing primary/secondary somatosensory area, thalamus, insula, prefrontal cortex, anterior cingulate cortex, basal ganglia, limbic system, brainstem, and cerebellum. The degrees of noxious stimulation and chronic spontaneous pain are associated with activity in the insula and the anterior cingulate cortex, which is involved in the emotional dimension of pain. Brain activation by allodynia is observed in the thalamus, prefrontal cortex, anterior cingulate, insula, and cerebellum and relates to attention and sensory-motor integration. Molecular neuroimaging studies indicate that the underlying pathophysiology of pain is related to the dopaminergic system, opioidergic system, and brain inflammation. Functional neuroimaging can elucidate the pathophysiology of acute and chronic pain syndromes, and thus objectively evaluate the degree of pain sensation, enabling us to plan pain control therapies for the future.