Premium
Unimpaired endogenous pain inhibition in the early phase of complex regional pain syndrome
Author(s) -
Kumowski N.,
Hegelmaier T.,
Kolbenschlag J.,
Maier C.,
Mainka T.,
Vollert J.,
EnaxKrumova E.
Publication year - 2017
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1002/ejp.988
Subject(s) - complex regional pain syndrome , quantitative sensory testing , medicine , anesthesia , threshold of pain , conditioning , classical conditioning , stimulus (psychology) , neuropathic pain , hyperalgesia , sensory system , nociception , psychology , neuroscience , receptor , psychotherapist , statistics , mathematics
Abstract Background The complex regional pain syndrome ( CRPS ) is characterized by distal generalisation of pain beyond the initial trauma. This might be the result of impaired endogenous pain inhibition. Method We compared Conditioned Pain Modulation ( CPM ) between patients with CRPS ( n = 24; pain: 4.5 ± 2.2, NRS 0–10; disease duration <1 year), neuralgia ( n = 17; pain: 5.5 ± 1.1) and healthy subjects ( n = 23) and its correlation with loss and gain of function as assessed by Quantitative Sensory Testing ( QST ). CPM was assessed with heat as test stimulus ( TS ) and cold water as conditioning stimulus ( CS ). The early CPM ‐effect was calculated as difference between heat pain during and before conditioning, the late CPM ‐effect, 5 minutes after and before conditioning, respectively. Results Heat pain decreased comparably after CS in all groups, resulting in a significant CPM ‐effect (healthy: −12.5 ± 12.4, NRS 0–100; CRPS : −14.7 ± 15.7; neuralgia: −7.9 ± 9.8; p < 0.001). When compared to healthy subjects, heat pain declined significantly steeper in CRPS patients (healthy: −2.0 ± 5.5, NRS 0–100/10 s; CRPS : −6.3 ± 8.1; p < 0.05). Only CRPS patients demonstrated a late CPM effect (−6.0 ± 9.0, p < 0.005). Neither spontaneous pain nor any QST parameter correlated with CPM , with the exception of a decreased cold pain threshold, which correlated with an enhanced CPM in CRPS patients only ( r = −0.456, p < 0.05). Conclusion An impairment of endogenous pain inhibition does not explain the extent of pain in the early stage of CRPS or in neuralgia. The unexpectedly high CPM in CRPS patients might result from activation of the intact descending pathways in response to central sensitization, as cold hyperalgesia correlated with the CPM ‐effect. Significance Conditioned pain modulation ( CPM ) is not impaired in the early phase of complex regional pain syndrome ( CRPS ) and neuralgia. Only in CRPS higher CPM was associated with lower cold pain thresholds.