title: Homotopic stimulation can reduce the area of allodynia in patients with neuropathic pain.
abstract: Allodynia is a common, troublesome feature of neuropathic pain conditions. In a previous study of postherpetic neuralgia we observed that repeated tactile stimulation appeared to reduce the size of the area of allodynia in some patients. We have undertaken a pragmatic clinical study to characterise this phenomenon in neuropathic pain patients with a range of different aetiologies. Neuropathic pain patients with a discrete area of tactile allodynia were recruited (n=20). We assessed the sensitive area using punctate and dynamic tactile stimuli, and thermal quantitative sensory testing. On two separate testing visits, the patients had repeated (10x over 1 min) noxious heat or cotton bud strokes applied to the affected site or contralaterally. Tactile stimulation of the affected area evoked pain (median 7 NRS) and a reduction (>30%) in the area of allodynia in 9/18 patients (maximum -48+/-9%, after 20 min), although the intensity of allodynic pain was unchanged. This effect persisted for over 1h and was present the following day in all patients tested (n=5/5). No subjects showed an increase in area after allodynic stimulation. There was no change in heat pain threshold at a distant site following allodynic stimulation, suggesting no activation of diffuse noxious inhibitory control. Repeated thermal noxious stimulation (median NRS 7) could also elicit changes (>30%) in the area of allodynia in some patients (reductions in 7/20, increases in 3/20). Thus, we have found that a brief period of homotopic painful stimulation can reduce the area of allodynia in around half of patients with established neuropathic pains.
authors.affiliation: Pain Clinic, Bristol Royal Infirmary, Bristol, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Love-Jones
authors.forename: Marie
authors.initials: M
authors.lastname: Besson
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Steeds
authors.forename: Peter
authors.initials: P
authors.lastname: Brook
authors.forename: Boris A
authors.initials: BA
authors.lastname: Chizh
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Pickering
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010525:Peripheral Nerves / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology / Q000628:therapy*; D010812:Physical Stimulation; D026741:Physical Therapy Modalities; D012867:Skin / Q000294:innervation / Q000503:physiopathology; D014110:Touch / Q000502:physiology*; D016896:Treatment Outcome