Painful peripheral neuropathy: Heterotopic noxious conditioning stimulation (HNC

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Eur J Pain. 2006 Aug 2

Heterotopic noxious conditioning stimulation (HNCS) reduced the

intensity of spontaneous pain, but not of allodynia in painful

peripheral neuropathy.

Tuveson B, Leffler AS, Hansson P.

Section of Clinical Pain Research, Department of Molecular Medicine

and Surgery, Karolinska Institute, SE-171 76 Stockholm, Sweden; Pain

Unit, Department of Anaesthesia and Intensive Care, Karolinska

Institute/Danderyd Hospital, SE-182 88 Stockholm, Sweden.

In 15 patients with painful peripheral neuropathy and dynamic

mechanical allodynia, the influence of spontaneous ongoing

neuropathic pain on pain sensitivity in a remote pain-free area was

examined, as was the influence of ischemia-induced heterotopic

noxious conditioning stimulation (HNCS) on the intensity of ongoing

pain and brush-evoked allodynia. In addition, the modulating effect

of HNCS on pain sensitivity in a pain-free area was investigated.

Pain thresholds to pressure and heat as well as the sensitivity to

suprathreshold pressure- and heat pain were assessed in the pain-free

area.

Dynamic mechanical allodynia was induced by a recently developed semi-

quantitative brushing technique and the patients continuously rated

the intensity of the allodynia using a computerized visual analogue

scale (VAS). The total brush-evoked pain intensity was calculated as

the area under the VAS curve. At baseline, no significant difference

in pain sensitivity was found between patients and their healthy

controls in the pain-free area, indicating a lack of activation of

pain modulatory systems from the spontaneous pain.

Compared to baseline, the patients rated the ongoing neuropathic pain

intensity significantly lower during the HNCS-procedure (p<0.05). In

contrast, there was no influence from HNCS on the total brush-evoked

pain intensity. In the pain-free area higher pressure pain thresholds

were demonstrated during conditioning stimulation in patients and

controls alike (p<0.01). In controls only, a significantly higher

heat pain threshold was found during the HNCS-procedure (p<0.01).

The main finding of the present study was that HNCS altered

differentially spontaneous and brush-provoked pain in patients with

painful peripheral neuropathy.