Conditioned pain modulation in patients with nonspecific chronic back pain with chronic local pain, chronic widespread pain, and fibromyalgia

Abstract

Findings considering conditioned pain modulation (CPM) in chronic back pain (CBP) are contradictory. This might be because many patients with CBP report pain in further areas of the body, and altered CPM might influence spatial extent of pain rather than CBP per se. Therefore, we compared CPM in patients with CBP with different pain extent. Patients with fibromyalgia syndrome (FMS), for whom CPM impairment is reported most consistently, were measured for comparison. Based on clinical evaluation and pain drawings, patients were categorized into chronic local back pain (CLP; n = 53), chronic widespread back pain (CWP; n = 32), and FMS (n = 92). Conditioned pain modulation was measured by the difference in pressure pain threshold (test stimuli) at the lower back before and after tonic heat pain (conditioning stimulus). We also measured psychosocial variables. Pressure pain threshold was significantly increased in CLP patients after tonic heat pain (P < 0.001) indicating induction of CPM. Conditioned pain modulation in CLP was significantly higher than that in CWP and FMS (P < 0.001), but CPM in CWP and FMS did not differ. Interestingly, a higher number of painful areas (0-10) were associated with lower CPM (r = 0.346, P = 0.001) in CBP but not in FMS (r = -0.013, P = 0.903). Anxiety and depression were more pronounced in FMS than in CLP or CWP (P values <0.01). Our findings suggest that CPM dysfunction is associated with CWP and not with FMS as suggested previously. FMS seems to differ from CWP without FMS by higher psychosocial burden. Moreover, patients with CBP should be stratified into CLP and CWP, and centrally acting treatments targeting endogenous pain inhibition seem to be more indicated the higher the pain extent.

Understanding the pain profile in patients with haemophilia: Impaired descending pain inhibition as measured by conditioned pain modulation

“…In chronic low back pain, a reduced CPM result is associated with a larger spatial extent of pain. 23 In order to obtain significant pain relief and to also prevent our already vulnerable patients from experiencing increased and extended pain, treatment based on the presence of dysfunctional endogenous pain inhibition should be a substantial aim of individual pain management regimens. Hence, a comprehensive pain diagnostic should involve different diagnostic tools capable of assessing the entire pain processing system.…”

“…Patients with haemophilia presented a more impaired total WFH physical examination score (median [IQR] PwH: 20 [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Likewise, the analysis of the severity of chronic pain showed a statistically significant difference between PwH and controls (P < .001) ( Table 1). Table 2).…”

Effects of repeated conditioning pain modulation in healthy volunteers

“…No other studies have compared repeated CPM‐bouts with Control bouts but four studies have successfully repeated two CPM‐bouts in healthy controls within the same session to evaluate reliability (Julien et al., ; Potvin and Marchand, ; Gerhardt et al., ). One study assessed CPM‐effects three times using a fixed conditioning intensity (Granovsky et al., , ; Imai et al., ; Vaegter et al., ).…”

“…Impaired CPM‐effect has been linked to local painful conditions including knee pain (Arendt‐Nielsen et al., ; Rathleff et al., ) and widespread pain such as fibromyalgia (Julien et al., ; Potvin and Marchand, ; Gerhardt et al., ). Yet, some studies compare the conditioned test‐stimulus to a single, unconditioned test‐stimulus (Granovsky et al., , ; Imai et al., ; Vaegter et al., ) while others use an average of two or more test‐stimuli to compare with a single conditioned test‐stimulus (Rathleff et al., ; Stolzman and Bement, ; Stolzman and Hoeger Bement, ; Skovbjerg et al., ; Vaegter et al., ).…”

Endocannabinoids and Related Lipids in Chronic Pain: Analytical and Clinical Aspects

“…The endogenous pain inhibitory ability has been studied in humans by conditioned pain modulation (CPM) activation (similar to diffuse noxious inhibitory controls (DNIC) in rats) and relies on the analgesic effect of a conditioning stimulus on a painful test stimulus ('pain inhibits pain') [11]. Deficit CPM has been reported in several chronic pain conditions [12,13]. However, sensitization can only be measured in settings where both input and output of a neural system are known (i.e., in animal experiments).…”