Positron emission tomography study of a chronic pain patient successfully treated with somatosensory thalamic stimulation.

Previous neuroimaging studies suggested that the neuronal network underlying the perception of chronic pain may differ from that underlying acute pain. To further map the neural network associated with chronic pain, we used positron emission tomography (PET) to determine significant regional cerebral blood flow (rCBF) changes in a patient with chronic facial pain. The patient is implanted with a chronic stimulation electrode in the left ventroposterior medial thalamic nucleus with which he can completely suppress his chronic pain. The patient was scanned in the following conditions: before thalamic stimulation (pain, no stimulation), during thalamic stimulation (no pain, stimulation) and after successful thalamic stimulation (no pain, no stimulation). Comparing baseline scans during pain with scans taken after stimulation, when the patient had become pain-free, revealed significant rCBF increases in the prefrontal (Brodmann areas (BA) 9, 10, 11 and 47) and anterior insular cortices, hypothalamus and periaqueductal gray associated with the presence of chronic pain. No significant rCBF changes occurred in thalamus, primary and secondary somatosensory cortex and anterior cingulate cortex, BA 24'. Significant rCBF decreases were observed in the substantia nigra/nucleus ruber and in the anterior pulvinar nucleus. During thalamic stimulation, blood flow significantly increased in the amygdala and anterior insular cortex. These data further support that there are important differences in the cerebral processing of acute and chronic pain.