Andreas Gerhardt

Pain perception in athletes compared to normally active controls: a systematic review with meta-analysis.

Summary Differences in pain perception between athletes and nonathletes were meta‐analyzed. Available data suggest that regular physical activity is associated with specific alterations in pain perception. ABSTRACT This study systematically reviewed differences in pain perception between athletes and normally active controls. We screened MEDLINE, Sport‐Discus, EMBASE, Web of Science, PsycINFO, PSYNDEX, and the citations of original studies and systematic reviews. All studies on experimentally induced pain that compared pain perception between athletes and normally active controls were eligible. The main outcome measures were pain tolerance and pain threshold. Effects are described as standardized mean differences and were pooled using random‐effects models. Fifteen studies including 899 subjects met the inclusion criteria. Twelve of these studies assessed pain tolerance, and 9 studies examined pain threshold. A meta‐analysis of these studies revealed that athletes possessed higher pain tolerance compared to normally active controls (effect size calculated as Hedges’ g = 0.87, 95% confidence interval [CI95] 0.53–1.21; P < 0.00001), whereas available data on pain threshold were less uniform (Hedges’ g = 0.69, CI95 0.16–1.21; P = 0.01). After exclusion of studies with high risk of bias, differences between groups in pain threshold were not significant any longer. Our data suggest that regular physical activity is associated with specific alterations in pain perception. Psychological and biological factors that may be responsible for these alterations are discussed.

Quantitative sensory testing profiles in chronic back pain are distinct from those in fibromyalgia.

ObjectivesAlterations in the central nervous system leading to higher pain sensitivity have been shown in both chronic back pain (CBP) and fibromyalgia syndrome (FMS). The aim of this study was to disclose commonalities and differences in the pathophysiology of FMS and CBP. MethodsWe used the quantitative sensory testing protocol of the German Research Network on Neuropathic Pain to obtain comprehensive profiles of somatosensory functions. The protocol comprised thermal and mechanical detection and pain thresholds, vibration thresholds, and pain sensitivity to sharp and blunt mechanical stimuli. We studied 21 FMS patients (mean pain duration: 13.4 y), 23 CBP subjects (mean pain duration: 15.9 y), and 20 healthy controls (HCs). Each participant received the test battery on the back and on the dorsal hand (pain-free control site). ResultsOn the back, FMS patients showed increased thermal and mechanical pain sensitivity compared with HCs and CBP participants. On the hand dorsum, FMS patients showed higher mechanical pain sensitivity compared with CBP participants and HCs and higher cold pain sensitivity compared with HCs. CBP participants showed increased pressure pain sensitivity and lower vibration sensitivity on the back, but no significant differences on the hand dorsum compared with HCs. DiscussionFMS patients showed increased sensitivity for different pain modalities at all measured body areas, suggesting central disinhibition as a potential mechanism. CBP participants in contrast, showed localized alterations within the affected segment possibly due to peripheral sensitization.

Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): Reference data for the trunk and application in patients with chronic postherpetic neuralgia

Summary A new set of reference data on the trunk for male and female healthy subjects is presented and applied to patients with postherpetic neuralgia. ABSTRACT Age‐ and gender‐matched reference values are essential for the clinical use of quantitative sensory testing (QST). To extend the standard test sites for QST—according to the German Research Network on Neuropathic Pain—to the trunk, we collected QST profiles on the back in 162 healthy subjects. Sensory profiles for standard test sites were within normal interlaboratory differences. QST revealed lower sensitivity on the upper back than the hand, and higher sensitivity on the lower back than the foot, but no systematic differences between these trunk sites. Age effects were significant for most parameters. Females exhibited lower pressure pain thresholds (PPT) than males, which was the only significant gender difference. Values outside the 95% confidence interval of healthy subjects (considered abnormal) required temperature changes of >3.3–8.2 °C for thermal detection. For cold pain thresholds, confidence intervals extended mostly beyond safety cutoffs, hence only relative reference data (left‐right differences, hand‐trunk differences) were sufficiently sensitive. For mechanical detection and pain thresholds, left‐right differences were 1.5–2.3 times more sensitive than absolute reference data. The most sensitive parameter was PPT, where already side‐to‐side differences >35% were abnormal. Compared to trunk reference data, patients with postherpetic neuralgia exhibited thermal and tactile deficits and dynamic mechanical allodynia, mostly without reduced mechanical pain thresholds. This pattern deviates from other types of neuropathic pain. QST reference data for the trunk will also be useful for patients with postthoracotomy pain or chronic back pain.

Alterations in endogenous pain modulation in endurance athletes: an experimental study using quantitative sensory testing and the cold-pressor task.

&NA; Athletes were significantly less sensitive to mechanical pain but showed higher sensitivity to vibration compared with normally active controls. Assessment of conditioned pain modulation suggests that the endogenous pain‐inhibitory system is less responsive in athletes. &NA; There is evidence for long‐term alterations in pain tolerance among athletes compared with normally active controls. However, scientific data on pain thresholds in this population are inconsistent, and the underlying mechanisms for the differences remain unclear. Therefore, we assessed differences and similarities in pain perception and conditioned pain modulation (CPM) at rest in endurance athletes and normally active controls. The standardised quantitative sensory testing protocol (QST) of the ‘German‐Research‐Network‐on‐Neuropathic‐Pain’ was used to obtain comprehensive profiles on somatosensory functions. The protocol consisted of thermal and mechanical detection as well as pain thresholds, vibration thresholds, and pain sensitivity to sharp and blunt mechanical stimuli. CPM (the diffuse‐noxious‐inhibitory‐control‐like effect) was measured using 2 tonic heat pain test stimuli (at the temperature exceeding a subjective pain rating of 50/100) separated by a 2‐min cold‐pressor task (CPM‐TASK; conditioning stimulus). Pain ratings were measured with a numerical rating scale. Endurance capacity was validated by assessment of maximum oxygen uptake (VO2max). Participants included 25 pain‐free male endurance athletes (VO2max > 60 mL/min * kg) and 26 pain‐free normally active controls (VO2max < 45 mL/min * kg) matched based on age and body mass index. Athletes were significantly less sensitive to mechanical pain but showed higher sensitivity to vibration (P < 0.05). In athletes, CPM was significantly less activated by the conditioning stimuli (P < 0.05) when compared with normally active controls. Our data show that somatosensory processing in athletes differs in comparison with controls, and suggest that the endogenous pain inhibitory system may be less responsive. This finding may explain the paradoxical propensity of athletes to develop chronic widespread pain.

The Prevalence and Type of Axis-I and Axis-II Mental Disorders in Subjects with Non-Specific Chronic Back Pain: Results from a Population-Based Study

OBJECTIVE To investigate the prevalence and the type of mental comorbidity in a population-based sample of subjects with non-specific chronic back pain. DESIGN Representative population-based survey. SETTING The city of Heidelberg (in southwestern Germany) and 10 adjacent communities. PATIENTS From a random sample of individuals (N = 2,000), 1,091 subjects completed a questionnaire including a pain assessment. Of those, 188 subjects (17%) fulfilled the criteria for chronic back pain (≥45 days of back pain in the last 3 months) and were subsequently invited to undergo a detailed clinical examination; 131 subjects (70%) agreed to participate. The Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) (SCID-I + II) was used to assess current (defined as the previous 4 weeks) mental comorbidity and was completed in 110 subjects (84%) with non-specific chronic back pain. INTERVENTION   N/A. OUTCOME MEASURES   DSM-IV mental comorbidity diagnoses. RESULTS The overall prevalence of mental comorbidity of Axis-I and -II disorders were 35.5% and 15.5%, respectively. Of Axis-I disorders, anxiety disorders (20.9%) and affective disorders (12.7%) were the most frequent. Of Axis-II disorders, 9.1% of diagnoses was of the Cluster C category (anxious/inhibited). Compared with the general population, the total rate of Axis-I comorbidity was significantly higher, while the total rate for Axis-II personality disorders was only slightly different. CONCLUSIONS The consistent diagnoses of anxiety, fear, and avoidance in these subjects indicate that also primary care health professionals should consider anxiety disorders in patients with chronic pain, in addition to the affective disorders that are most frequently self-reported in pain patients.

Altered pressure pain thresholds and increased wind-up in adult patients with chronic back pain with a history of childhood maltreatment: a quantitative sensory testing study.

Abstract Childhood maltreatment (CM) has been associated with an increased risk of nonspecific chronic low back pain (nsCLBP). However, the mechanisms underlying this association are unclear. Therefore, this study considered whether distinct types of CM are accompanied by specific alterations in somatosensory function. A total of 176 subjects with nsCLBP and 27 pain-free controls (PCs) were included. The Childhood Trauma Questionnaire (CTQ) was used to categorize patients into 2 groups (abused/neglected vs nonabused/nonneglected) for 5 types of CM (emotional abuse, physical abuse, sexual abuse, emotional neglect, and physical neglect). The standardized quantitative sensory testing protocol of the “German Research Network on Neuropathic Pain” was performed to obtain comprehensive profiles on somatosensory function, including detection and pain thresholds, pain sensitivity, and assessments of temporal summation (wind-up). Between 17.7% and 51.4% of subjects with nsCLBP reported CM, depending on the type of CM. Childhood Trauma Questionnaire subscores for emotional and sexual abuse were significantly higher in subjects with nsCLBP than in PCs. Compared with PCs, subjects with CM showed reduced pressure pain thresholds (PPTs), irrespective of the type of CM. Regarding distinct types of CM, subjects with nsCLBP with emotional abuse reported significantly higher wind-up than those without, and sexual abuse was accompanied by enhanced touch sensitivity. Our findings suggest that CM is nonspecifically associated with a decreased PPT in nsCLBP. Emotional abuse apparently leads to enhanced spinal pain summation, and sexual abuse leads to enhanced touch sensitivity. These results emphasize the importance of emotional abuse in nsCLBP and suggest that CM can induce long-term changes in adult somatosensory function.

Distinct quantitative sensory testing profiles in nonspecific chronic back pain subjects with and without psychological trauma.

Abstract Psychological trauma is associated with an increased risk for chronification of nonspecific chronic back pain (nsCLBP) independent of posttraumatic stress disorder (PTSD). However, the mechanisms underlying the role of psychological trauma in nsCLBP are less clear than in PTSD. Therefore, this study considered whether psychological trauma exposure (TE) is accompanied by specific alterations in pain perception. The study included 56 participants with nsCLBP and TE (nsCLBP-TE), 93 participants with nsCLBP without TE (nsCLBP-W-TE), and 31 pain-free controls. All participants underwent a thorough clinical evaluation. The standardized quantitative sensory testing protocol of the “German Research Network on Neuropathic Pain” was used to obtain comprehensive profiles on somatosensory functions in painful (back) and non-painful areas (hand). The protocol consisted of thermal and mechanical detection as well as pain thresholds, vibration thresholds, and pain sensitivity to sharp and blunt mechanical stimuli. Psychological trauma was validated by structured clinical interview. Trauma-associated symptom severity, anxiety, and depressive symptomatology were assessed by self-report questionnaires. Differences in somatosensory function were seen only for pressure pain thresholds. Compared with controls, nsCLBP-TE revealed hyperalgesia generalized in space with lower thresholds in painful and non-painful areas, whereas nsCLBP-W-TE demonstrated localized alterations with decreased thresholds only in the pain-affected area of the back (P ⩽ 0.006). Our findings suggest an augmented central pain processing in nsCLBP-TE (alterations in painful and non-painful areas), whereas nsCLBP-W-TE show only local changes (alterations only in the painful area) suggesting regional sensitization processes. This finding might explain why TE without PTSD is associated with an increased prevalence of chronic pain.

The Prevalence Rate and the Role of the Spatial Extent of Pain in Nonspecific Chronic Back Pain—A Population-Based Study in the South-West of Germany

OBJECTIVE To determine the prevalence of chronic back pain in the general population and to establish an evidence-based subclassification system for chronic back pain based on pain extent. DESIGN Representative population-based survey. SETTING South-western Germany. SUBJECTS Four-thousand representative residents were contacted. The corrected response rate was 61.8% (N = 2,408). Those suffering from chronic back pain (pain ≥45 days/last 3 months) were invited to a clinical evaluation. OUTCOME MEASURES Chronic back pain, spatial extent of pain, sociodemographic and clinical variables. RESULTS Age- and sex-adjusted prevalence rate for chronic back pain was 17.7%. Analyzing pain extent, we found that only 19.6% suffered strictly from chronic local back pain, while the majority indicated additional pain regions. Thus, we developed a subclassification system based on pain extent that consists of four more homogeneous groups (19.6% strict chronic local pain, 42.1% chronic regional pain, 24.3% common chronic widespread pain, 13.9% extreme chronic widespread pain). Interestingly, in this system, increasing pain extent was significantly associated with higher distress, as reflected by sociodemographic (e.g., lower education, lower social class, and higher application rate for disability pension) and clinical variables (e.g., higher pain intensity, more pain medication, more consultations, higher impairment, and lower quality of life). CONCLUSIONS Chronic back pain is prevalent and usually involves additional pain areas outside of the back. This challenges the concept of chronic back pain as a distinct entity. To identify patients who are distressed by chronic back pain, a four-class taxonomy based on pain drawings is both feasible and clinically useful.

Chronic Widespread Back Pain is Distinct From Chronic Local Back Pain: Evidence From Quantitative Sensory Testing, Pain Drawings, and Psychometrics.

Objectives:Whether chronic localized pain (CLP) and chronic widespread pain (CWP) have different mechanisms or to what extent they overlap in their pathophysiology is controversial. The study compared quantitative sensory testing profiles of nonspecific chronic back pain patients with CLP (n=48) and CWP (n=29) with and fibromyalgia syndrome (FMS) patients (n=90) and pain-free controls (n = 40). Materials and Methods:The quantitative sensory testing protocol of the “German-Research-Network-on-Neuropathic-Pain” was used to measure evoked pain on the painful area in the lower back and the pain-free hand (thermal and mechanical detection and pain thresholds, vibration threshold, pain sensitivity to sharp and blunt mechanical stimuli). Ongoing pain and psychometrics were captured with pain drawings and questionnaires. Results:CLP patients did not differ from pain-free controls, except for lower pressure pain threshold (PPT) on the back. CWP and FMS patients showed lower heat pain threshold and higher wind-up ratio on the back and lower heat pain threshold and cold pain threshold on the hand. FMS showed lower PPT on back and hand, and higher comorbidity of anxiety and depression and more functional impairment than all other groups. Discussion:Even after long duration CLP presents with a local hypersensitivity for PPT, suggesting a somatotopically specific sensitization of nociceptive processing. However, CWP patients show widespread ongoing pain and hyperalgesia for different stimuli that is generalized in space, suggesting the involvement of descending control systems, as also suggested for FMS patients. Because mechanisms in nonspecific chronic back pain with CLP and CWP differ, these patients should be distinguished in future research and allocated to different treatments.

Subgroups of musculoskeletal pain patients and their psychobiological patterns – The LOGIN study protocol

BackgroundPain conditions of the musculoskeletal system are very common and have tremendous socioeconomic impact. Despite its high prevalence, musculoskeletal pain remains poorly understood and predominantly non-specifically and insufficiently treated.The group of chronic musculoskeletal pain patients is supposed to be heterogeneous, due to a multitude of mechanisms involved in chronic pain. Psychological variables, psychophysiological processes, and neuroendocrine alterations are expected to be involved. Thus far, studies on musculoskeletal pain have predominantly focused on the general aspects of pain processing, thus neglecting the heterogeneity of patients with musculoskeletal pain. Consequently, there is a need for studies that comprise a multitude of mechanisms that are potentially involved in the chronicity and spread of pain. This need might foster research and facilitate a better pathophysiological understanding of the condition, thereby promoting the development of specific mechanism-based treatments for chronic pain. Therefore, the objectives of this study are as follows: 1) identify and describe subgroups of patients with musculoskeletal pain with regard to clinical manifestations (including mental co-morbidity) and 2) investigate whether distinct sensory profiles or 3) distinct plasma levels of pain-related parameters due to different underlying mechanisms can be distinguished in various subgroups of pain patients.Methods/DesignWe will examine a population-based chronic pain sample (n = 100), a clinical tertiary care sample (n = 100) and pain-free patients with depression or post-traumatic stress disorder and pain-free healthy controls (each n = 30, respectively). The samples will be pain localisation matched by sex and age to the population-based sample. Patients will undergo physical examination and thorough assessments of mental co-morbidity (including psychological trauma), perceptual and central sensitisation (quantitative sensory testing), descending inhibition (conditioned pain modulation, the diffuse noxious inhibitory control-like effect), as well as measurement of the plasma levels of nerve growth factor and endocannabinoids.DiscussionThe identification of the underlying pathophysiologic mechanisms in different subgroups of chronic musculoskeletal pain patients will contribute to a mechanism-based subgroup classification. This will foster the development of mechanism-based treatments and holds promise to treat patients more sufficient.