title: A positron emission tomography study of wind-up pain in chronic postherniotomy pain.
abstract: Many neuropathic pain conditions are characterized by abnormal responses to noxious or innocuous mechanical stimulation, including wind-up pain. Whereas previous brain imaging studies have explored the cerebral correlates of hyperalgesia and allodynia, no studies are available on mechanical-induced wind-up pain in neuropathic pain patients. We therefore used positron emission tomography (PET) to investigate the cerebral response pattern of mechanical wind-up pain in a homogenous group of 10 neuropathic pain patients with long-standing postherniotomy pain in the groin area. Patients were scanned in the following conditions: (1) rest; (2) wind-up pain, induced by 2 Hz von Frey stimulation in the painful area; (3) non-painful 2 Hz von Frey stimulation in the homologous contralateral area and (4) tonic pressure pain in the homologous contralateral area. A direct comparison between wind-up pain and non-painful von Frey stimulation revealed that the former more strongly activated contralateral secondary somatosensory cortex, insula, anterior cingulate cortex, right dorsolateral prefrontal cortex, thalamus and cerebellum. In addition, wind-up pain also activated the sublenticular extended amygdala (SLEA) and the brain stem. A direct comparison between wind-up pain and pressure pain revealed that both activated a largely overlapping network. Since no de novo brain areas were activated by wind-up pain, our data suggest that the processes specific to wind-up pain do not occur at the cerebral level.
authors.affiliation: Dept. of Surgical Pathophysiology, Rigshospitalet, Copenhagen University, Copenhagen, Denmark. ron@pet.rh.dk
authors.forename: Ron
authors.initials: R
authors.lastname: Kupers
authors.forename: Markus Nowak
authors.initials: MN
authors.lastname: Lonsdale
authors.forename: Eske
authors.initials: E
authors.lastname: Aasvang
authors.forename: Henrik
authors.initials: H
authors.lastname: Kehlet
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging*; D001931:Brain Mapping; D059685:Herniorrhaphy / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000000981:diagnostic imaging* / Q000209:etiology; D059906:Neuroimaging; D010147:Pain Measurement; D010812:Physical Stimulation; D011877:Radionuclide Imaging