Evidence for spinal cord hypersensitivity in chronic pain after whiplash injury and in fibromyalgia

Abstract

Patients with chronic pain after whiplash injury and fibromyalgia patients display exaggerated pain after sensory stimulation. Because evident tissue damage is usually lacking, this exaggerated pain perception could be explained by hyperexcitability of the central nervous system. The nociceptive withdrawal reflex (a spinal reflex) may be used to study the excitability state of spinal cord neurons. We tested the hypothesis that patients with chronic whiplash pain and fibromyalgia display facilitated withdrawal reflex and therefore spinal cord hypersensitivity. Three groups were studied: whiplash (n=27), fibromyalgia (n=22) and healthy controls (n=29). Two types of transcutaneous electrical stimulation of the sural nerve were applied: single stimulus and five repeated stimuli at 2 Hz. Electromyography was recorded from the biceps femoris muscle. The main outcome measurement was the minimum current intensity eliciting a spinal reflex (reflex threshold). Reflex thresholds were significantly lower in the whiplash compared with the control group, after both single (P=0.024) and repeated (P=0.035) stimulation. The same was observed for the fibromyalgia group, after both stimulation modalities (P=0.001 and 0.046, respectively). We provide evidence for spinal cord hyperexcitability in patients with chronic pain after whiplash injury and in fibromyalgia patients. This can cause exaggerated pain following low intensity nociceptive or innocuous peripheral stimulation. Spinal hypersensitivity may explain, at least in part, pain in the absence of detectable tissue damage.

Quantitative sensory testing somatosensory profiles in patients with cervical radiculopathy are distinct from those in patients with nonspecific neck–arm pain

“…These differing observations may be indicative of the heterogeneity of FM and the possible existence of various sub-groups [34,29,55]. In the absence of evidence of tissue damage in FM, aberrations in pain inhibitory [39,35,45] and pain facilitatory mechanisms [45] as well as central sensitisation/augmentation of sensory input [19,2,62] have been associated with enhanced pain sensitivity in FM.…”

“…(1) the sensory phenotypes between the two neck-arm pain groups would be different; (2) in patients with cervical radiculopathy localised sensory abnormalities would be restricted to the maximal pain area and to the area of dermatomal sensory loss; (3) in patients with NSNAP sensory abnormalities would be found only in the maximal pain area; and 4) sensory profiles of the neck-arm pain groups would differ from that of patients with FM.…”

Defensive reflexes in people with pain – a biomarker of the need to protect? A meta-analytical systematic review

“…There were 19 studies that met the inclusion criteria for the review but could not be included in the meta-analyses because raw data could not be extracted (Peters et al, 1992;Leroux et al, 1995;Knost et al, 1997;de Tommaso et al, 2000;Nappi et al, 2002;Desmeules et al, 2003;Katsarava et al, 2003;Banic et al, 2004;Lang et al, 2005;Ayzenberg et al, 2006;Carleton et al, 2006;Sandrini et al, 2006;Al-Azzawi et al, 2008;Filatova et al, 2008;Mendak et al, 2010;Neziri et al, 2010;Biurrun Manresa et al, 2013a,b;Desmeules et al, 2014). We were unable to obtain a meaningful outcome relevant to our research question for eight studies (see Table 2 for details).…”

“…For example, for five studies, the authors were unable to access their data (Peters et al, 1992;Knost et al, 1997;Nappi et al, 2002;Katsarava et al, 2003;Sandrini et al, 2006), two considered that it was inappropriate to use their data and declined to share their results (Carleton et al, 2006;Biurrun Manresa et al, 2013a,b), and the authors of nine studies did not respond to several enquiries about their data (Leroux et al, 1995;de Tommaso et al, 2000;Desmeules et al, 2003Desmeules et al, , 2014Banic et al, 2004;Lang et al, 2005;Ayzenberg et al, 2006;Al-Azzawi et al, 2008;Mendak et al, 2010). As noted in the peer review process of the current review, this does reflect a kind of bias -towards papers the authors of which are willing and able to share their data for the purposes of the meta-analysis.…”

Associations between cognitive performance and pain in chronic fatigue syndrome: comorbidity with fibromyalgia does matter

“…Chronic widespread musculoskeletal pain is the hallmark symptom of fibromyalgia (FM), and furthermore it is known that patients with CFS and patients with FM share many other symptoms and clinical features such as fatigue, sleep disturbances, cognitive dysfunction, and mood disturbances (2)(3)(4)(5). A growing body of scientific literature designates central sensitisation (CS) as a common pathophysiological mechanism in these overlapping conditions (6)(7)(8)(9).…”