Expansion of nociceptive reflex receptive fields in patients with low back and neck pain

A.Y. NEZIRI; J.A. BIURRUN MANRESA; P. JÜNI; L. ARENDT-NIELSEN; O.K. ANDERSEN; M. CURATOLO

Hamburgo

Congreso; 7th Congress of the European Federation of Pain Chapters (EFIC); 2011

Background and Aims: Expansion of receptive fields of spinal cord neurons may be one of the mechanisms underlying central hypersensitivity, and can be measured in humans with a new method involving nociceptive reflexes. We tested the hypothesis that patients with low back pain and neck pain display an expansion of nociceptive reflex receptive fields. Methods: 40 patients with chronic low back pain, 40 with chronic neck pain and 14 with acute low back pain (data collection is running) were tested and compared with a cohort of 300 pain-free subjects. All subjects were tested by the same investigator (A.N.). Electrical stimuli were applied to 10 sites of the foot sole to evoke reflexes in the tibialis anterior muscle. The reflex receptive field area was defined as the area of the foot sole (expressed as fraction of the foot sole) from which a muscle contraction was evoked by the electrical stimulus. The groups were compared by Kruskal?Wallis ANOVA on ranks and Multiple Comparisons versus control group. Results: All three patient groups displayed significantly larger RRF area, compared with pain-free subjects. Medians (25 and 75 percentiles, p-value compared to controls) were: acute low back pain 0.46 (0.33?0.52, p = 0.004), chronic low back pain 0.39 (0.26? 0.55, p = 0.047), chronic neck pain 0.40 (0.29?0.48, p = 0.006) and control group 0.30 (0.18?0.44). No significant differences between patients were observed. Conclusions: This study provides the first evidence for widespread expansion of reflex receptive fields in acute and chronic musculoskeletal pain.