Chronic pain due to brachial plexus avulsion (BPA) is a kind of refractory neuropathic pain, yet there is a lack of knowledge regarding underlying brain activity. To further identify brain regions involved in chronic pain due to BPA, fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) was used to observe brain glucose metabolic changes in those patients. Five patients with chronic pain due to left-BPA, whose pain reduced more than 75% after dorsal root entry zoneotomy (DREZotomy) were selected. The visual analog scale (VAS) , Hamilton depression scale, Hamilton anxiety scale and ¹⁸F-FDG PET of brain were recorded before and 14 days after DREZotomy respectively. Statistical parametric mapping 2 (SPM2) was applied for data analysis. Comparing with PET during pain before DREZotomy, PET after DREZotomy showed significant glucose metabolism decreases in bilateral caudate, orbitofrontal cortex (OFC) (BA11), contralateral subgenual cingulate (BA25) and ipsilateral dorsolateral prefrontal cortex (DLPFC) (BA46/47), and significant glucose metabolism increases in contralateral thalamus, pulvinar and ipsilateral parietal lobe (BA7). The results suggested that the brain areas involved in emotion, attention and internal modulation of pain play an important role in the modulation of chronic pain due to BPA.