Decreasing Pain Ratings in Chronic Arm Pain Through Changing a Virtual Body: Different Strategies for Different Pain Types

Modifying the visual aspect of a virtual arm that is felt as one's own using immersive virtual reality (VR) modifies pain threshold in healthy subjects, but does it modify pain ratings in chronic pain patients? Our aim was to investigate whether varying properties of a virtual arm co-located with the real arm modulated pain ratings in patients with chronic arm/hand pain because of complex regional pain syndrome (CRPS) type I (without nerve injury) or peripheral nerve injury (PNI). CRPS (n = 9) and PNI (n = 10) patients were immersed in VR and the virtual arm was shown at 4 transparency levels (transparency test) and 3 sizes (size test). We evaluated pain ratings throughout the conditions and assessed the virtual experience, finding that patients with chronic pain can achieve levels of ownership and agency over a virtual arm similar to healthy participants. All 7 conditions globally decreased pain ratings by half. Increasing transparency decreased pain in CRPS but did the opposite in PNI, whereas increasing size slightly increased pain ratings only in CRPS. We conclude that embodiment in VR can decrease pain ratings in chronic arm pain, although the type of pain determines which strategy to decrease pain is most useful. We discuss this through the interactions between body image and pain perception.Perspective“Embodiment” in VR is useful to decrease pain ratings in chronic pain patients, but the best strategy needs to be tuned to the pain etiology. This approach could potentially help patients with chronic pain and clinicians who seek alternatives to pain management for patients.     

Responses to a clinical test of mechanical provocation of nerve tissue in whiplash associated disorder

Involvement of nerve tissue may contribute to the persistence of pain following a whiplash injury. This study aimed to investigate responses to the brachial plexus provocation test (BPPT) in 156 subjects with chronic whiplash associated disorder (WAD) with and without associated arm pain and 95 asymptomatic control subjects. The range of elbow extension (ROM) and visual analogue scale (VAS) pain scores were measured. Subjects with chronic WAD demonstrated significantly less ROM and higher VAS scores with the BPPT than the asymptomatic subjects (P<0.001). These effects occurred bilaterally. Within the whiplash population, subjects whose arm pain was reproduced by the BPPT demonstrated significantly less ROM on both the symptomatic and asymptomatic sides when compared to the whiplash subjects whose arm pain was not reproduced by the BPPT (P=0.003) and significantly less ROM and higher VAS scores than those whiplash subjects with no arm pain (P=0.003, 0.01). Only the whiplash subjects whose arm pain was reproduced by the BPPT demonstrated differences between the symptomatic and asymptomatic sides. These generalized hyperalgesic responses to the BPPT support the hypothesis of central nervous system hypersensitivity as contributing to persistent pain experienced by WAD patients.     

Associations Between Catecholaminergic and Serotonergic Genes and Persistent Arm Pain Severity Following Breast Cancer Surgery

Persistent arm pain is a common problem after breast cancer surgery. Little is known about genetic factors that contribute to this type of postsurgical pain. Study purpose was to explore associations between persistent arm pain phenotypes and genetic polymorphisms among 15 genes involved in catecholaminergic and serotonergic neurotransmission. Women (n = 398) rated the presence and intensity of arm pain monthly for 6 months after breast cancer surgery. Three distinct latent classes of patients were identified (ie, no arm pain [41.6%], mild arm pain (23.6%), and moderate arm pain (34.8%). Logistic regression analyses were used to evaluate for differences between genotype or haplotype frequencies and the persistent arm pain classes. Compared with the no arm pain class, 3 single nucleotide polymorphisms and 1 haplotype, in 4 genes, were associated with membership in the mild arm pain class: COMT rs4633, HTR2A haplotype B02 (composed of rs1923886 and rs7330636), HTR3A rs1985242, and TH rs2070762. Compared with the no arm pain class, 4 single nucleotide polymorphisms in 3 genes were associated with membership in the moderate arm pain class: COMT rs165656, HTR2A rs2770298 and rs9534511, and HTR3A rs1985242. Findings suggest that variations in catecholaminergic and serotonergic genes play a role in the development of persistent arm pain.PerspectiveLimited information is available on genetic factors that contribute to persistent arm pain after breast cancer surgery. Genetic polymorphisms in genes involved in catecholaminergic and serotonergic neurotransmission were associated with 2 persistent arm pain phenotypes. Findings may be used to identify patients are higher risk for this common pain condition.     

Identification of patient subgroups and risk factors for persistent arm/shoulder pain following breast cancer surgery

PurposeIn this prospective, longitudinal study, we extend our findings on persistent breast pain in patients (n = 398) following breast cancer surgery and evaluate the prevalence and characteristics of persistent pain in the arm/shoulder. In addition, differences in the severity of common symptoms and quality of life outcomes measured prior to surgery, among the arm pain classes, were evaluated.Methods and samplePatients were recruited from Breast Care Centers located in a Comprehensive Cancer Center, two public hospitals, and four community practices. Patients were assessed prior to and monthly for six months following breast cancer surgery.ResultsUsing growth mixture modeling, patients were classified into no (41.6%), mild (23.6%), and moderate (34.8%) arm pain classes based on ratings of worst arm/shoulder pain. Compared to the no pain class, patients in the moderate pain class were significantly younger, had a higher body mass index, and were more likely to report preoperative breast pain and swelling in the affected breast. In addition, patients in the moderate pain class reported higher levels of depression, anxiety, and sleep disturbance than the no pain class.ConclusionsFindings suggest that approximately 35% of women experience persistent levels of moderate arm/shoulder pain in the first six months following breast cancer surgery. Moderate arm/shoulder pain is associated with clinically meaningful decrements in functional status and quality of life.     

The influence of pain intensity on somatosensory perception in patients suffering from subacute/chronic lateral epicondylalgia.

A confounding factor in the analysis of chronic pain patients is the finding of signs of somatosensory disturbances not only in neuropathic pain patients but also in a subgroup of patients with musculoskeletal pain. The purpose was to investigate if patients suffering from subacute/chronic lateral epicondylalgia demonstrated altered sensibility, and if this was affected by pain intensity. At the start of the experiment, quantitative sensory testing (QST) (thermal, pressure pain, touch) was performed in the local pain area and in the area of pain referral. QST was repeated following pain provocation (weight lifting). A local anaesthetic was then injected into the lateral epicondyle and QST was repeated in the area of pain referral. The contralateral arm was assessed, treated and injected in the same way. At the baseline assessment there was no difference in sensibility between sides, with the exception of a significantly lowered threshold to noxious heat (p<0.04) in the area of pain referral, present during the whole experiment. In the affected arm only, weight lifting resulted in significantly increased pain intensity in the local (p<0.01) and referred (p<0.01) pain areas, respectively. Repeated muscle contractions resulted in altered somatosensory functions in both the affected arm and the unaffected arm, consequently not dependent on ongoing pain in the assessed area. Tactile perception thresholds increased significantly following pain provocation in the area of pain referral (p<0.04) only and normalized following injection of local anaesthetic (p<0.02), indicating that the sensitivity to light touch was altered by the nociceptive input from the affected arm.     

血小板激活因子在颈椎间盘突出中的表达

目的:研究血小板激活因子(PAF)在颈椎间盘突出中的表达及其与颈肩痛的关系,为颈椎间盘突出症的临床康复治疗起指导作用.方法:以30例颈椎间盘突出症患者(突出组)手术取出的突出髓核组织用酶联免疫吸附法测定其PAF;另7例颈椎骨折患者(对照组)手术中所取的髓核组织作为正常对照.对颈椎间盘突出症所导致颈肩痛以达拉斯(Dallas)疼痛调查表作评分.结果:髓核组织中PAF 2组均存在,突出组含量明显高于对照组(P＜0.01),且PAF的含量与颈肩痛程度有相关性.结论:PAF与颈椎间盘突出引起的颈肩痛有明显相关性,使用康复措施阻止PAF等炎性因子的合成、释放、乃至清除,可能对改善颈肩痛有重要作用.     

Are the changes in postural control associated with low back pain caused by pain interference?

BACKGROUND: Voluntary limb movements are associated with involuntary and automatic postural adjustments of the trunk muscles. These postural adjustments occur prior to movement and prevent unwanted perturbation of the trunk. In low back pain, postural adjustments of the trunk muscles are altered such that the deep trunk muscles are consistently delayed and the superficial trunk muscles are sometimes augmented. This alteration of postural adjustments may reflect disruption of normal postural control imparted by reduced central nervous system resources available during pain, so-called "pain interference," or reflect adoption of an alternate postural adjustment strategy. METHODS: We aimed to clarify this by recording electromyographic activity of the upper (obliquus externus) and lower (transversus abdominis/obliquus internus) abdominal muscles during voluntary arm movements that were coupled with painful cutaneous stimulation at the low back. If the effect of pain on postural adjustments is caused by pain interference, it should be greatest at the onset of the stimulus, should habituate with repeated exposure, and be absent immediately when the threat of pain is removed. Sixteen patients performed 30 forward movements of the right arm in response to a visual cue (control). Seventy trials were then conducted in which arm movement was coupled with pain ("pain trials") and then a further 70 trials were conducted without the pain stimulus ("no pain trials"). RESULTS: There was a gradual and increasing delay of transversus abdominis/obliquus internus electromyograph and augmentation of obliquus externus during the pain trials, both of which gradually returned to control values during the no pain trials. CONCLUSION: The results suggest that altered postural adjustments of the trunk muscles during pain are not caused by pain interference but are likely to reflect development and adoption of an alternate postural adjustment strategy, which may serve to limit the amplitude and velocity of trunk excursion caused by arm movement.     

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

The aim of this study was to establish the somatosensory profiles of patients with cervical radiculopathy and patients with nonspecific neck–arm pain associated with heightened nerve mechanosensitivity (NSNAP). Sensory profiles were compared to healthy control (HC) subjects and a positive control group comprising patients with fibromyalgia (FM). Quantitative sensory testing (QST) of thermal and mechanical detection and pain thresholds, pain sensitivity and responsiveness to repetitive noxious mechanical stimulation was performed in the maximal pain area, the corresponding dermatome and foot of 23 patients with painful C6 or C7 cervical radiculopathy, 8 patients with NSNAP in a C6/7 dermatomal pain distribution, 31 HC and 22 patients with FM. For both neck–arm pain groups, all QST parameters were within the 95% confidence interval of HC data. Patients with cervical radiculopathy were characterised by localised loss of function (thermal, mechanical, vibration detection P < .009) in the maximal pain area and dermatome (thermal detection, vibration detection, pressure pain sensitivity P < .04), consistent with peripheral neuronal damage. Both neck–arm pain groups demonstrated increased cold sensitivity in their maximal pain area (P < .03) and the foot (P < .009), and this was also the dominant sensory characteristic in patients with NSNAP. Both neck–arm pain groups differed from patients with FM, the latter characterised by a widespread gain of function in most nociceptive parameters (thermal, pressure, mechanical pain sensitivity P < .027). Despite commonalities in pain characteristics between the 2 neck–arm pain groups, distinct sensory profiles were demonstrated for each group.     

身体上部加压服消除正加速度诱发臂痛的实验观察

目的 观察受试者在载人离心机上进行抗荷正压呼吸,身体上部着加压服时发生臂痛的性质、程度,并对其防护作用进行评价. 方法 被试者为 6名男性青年,正加速度(+ Gz)暴露时,先观察受试者穿中囊代偿背心和 65%大面积抗荷服( ECGS),在 5.0, 5.5, 6.0, 6.5, 7.0 G各持续 15 s时的臂痛程度和性质;休息 10 min后,受试者改穿身体上部加压服进行 7.0 G持续 15 s,观察臂痛缓解的程度. 结果 6名受试者均完成了本项实验.穿中囊背心的受试者,在 6.0, 6.5, 7.0 G时均有人出现不同程度的臂痛,疼痛发生的几率和程度与 G值的增高成正比.在 7.0 G时穿身体上部加压服后,双臂均无疼痛感. 结论身体上部加压服可以消除高+ Gz与 PBG引起的臂痛.     

Pathological muscle activation patterns in patients with massive rotator cuff tears, with and without subacromial anaesthetics

A mechanical deficit due to a massive rotator cuff tear is generally concurrent to a pain-induced decrease of maximum arm elevation and peak elevation torque. The purpose of this study was to measure shoulder muscle coordination in patients with massive cuff tears, including the effect of subacromial pain suppression. Ten patients, with MRI-proven cuff tears, performed an isometric force task in which they were asked to exert a force in 24 equidistant intervals in a plane perpendicular to the humerus. By means of bi-polar surface electromyography (EMG) the direction of the maximal muscle activation or principal action of six muscles, as well as the external force, were identified prior to, and after subacromial pain suppression. Subacromial lidocaine injection led to a significant reduction of pain and a significant increase in exerted arm force. Prior to the pain suppression, we observed an activation pattern of the arm adductors (pectoralis major pars clavicularis and/or latissimus dorsi and/or teres major) during abduction force delivery in eight patients. In these eight patients, adductor activation was different from the normal adductor activation pattern. Five out of these eight restored this aberrant activity (partly) in one or more adductor muscles after subacromial lidocaine injection. Absence of glenoid directed forces of the supraspinate muscle and compensation for the lost supraspinate abduction torque by the deltoideus leads to destabilizating forces in the glenohumeral joint, with subsequent upward translation of the humeral head and pain. In order to reduce the superior translation force, arm adductors will be co-activated at the cost of arm force and abduction torque. Pain seems to be the key factor in this (avoidance) mechanism, explaining the observed limitations in arm force and limitations in maximum arm elevation in patients suffering subacromial pathologies. Masking this pain may further deteriorate the subacromial tissues as a result of proximal migration of the humeral head and subsequent impingement of subacromial tissues.     

Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness

This study compares the effect of experimental muscle pain on deep tissue sensitivity and force attenuation in the wrist extensors of patients with lateral epicondylalgia (n=20), and healthy controls (n=20) with experimentally induced sensori-motor characteristics simulating lateral epicondylalgia. Delayed onset muscle soreness (DOMS) in wrist extensors of healthy controls was induced by eccentric exercise in one arm 24h prior to injection (Day 0). Saline-induced pain intensity (visual analogue scale, VAS), distribution, and quality were assessed quantitatively in both arms for both groups. Pressure pain thresholds (PPT) were assessed at three different sites in the wrist extensors. Maximal grip force and wrist extension force were recorded. In response to saline-induced pain in the extensor carpi radialis brevis, regardless of arm, the patient group demonstrated a significantly quicker pain onset (P<0.01), mapped larger pain areas and more referred pain areas, compared to healthy controls (P<0.03). Pain persisted significantly longer in the sore arm of the patient group, compared with all other arms (P<0.02). Patients demonstrated significant bilateral hyperalgesia at extensor carpi radialis brevis during and post saline-induced pain compared to pre-injection and healthy controls (P<0.04). The sore arm in patients and the DOMS arms in healthy subjects showed significantly reduced maximal force (P<0.0001), at all Day 1 times compared with the control arms. In patients, the bilateral increase in deep tissue sensitivity and enlarged referred pain areas during saline-induced pain might suggest involvement of central sensitisation.     

Mechanisms of pain referral in patients with whiplash associated disorder

The aim was to investigate the mechanisms of pain referral in patients with whiplash associated disorder. Pain was induced in 12 controls and 12 patients with whiplash associated disorder by intramuscular electrical stimulation in the infraspinatus muscle and the ipsilateral upper arm, i.e., the area where all subjects perceived referred pain during conditioning stimulation in the infraspinatus muscle. Conditioning stimulation amounted to a pain intensity rated as 2/10 and 4/10. During conditioning stimulation in the infraspinatus muscle, sensitivity to test stimuli was assessed in the referred pain area (i.e., upper arm) and vice versa. Test stimuli consisted of intramuscular electrical stimulation corresponding to innocuous perception threshold, electrical pain threshold, and pain intensities rated as 2/10, 4/10 and 6/10, respectively. Compared to controls, patients with whiplash associated disorder had increased pain sensitivity (p≤0.01) and indicated larger areas of referred pain ((p≤0.003) during stimulation at the infraspinatus muscle; p≤0.03 during stimulation at the upper arm), including proximal referral of pain which was never reported by controls (p≤0.05). During conditioning stimulation in the infraspinatus muscle (4/10) all subjects reported referred pain in the upper arm (corresponding to the test site) and innocuous perception thresholds (p<0.05)(patients) and electrical pain thresholds (p<0.001) (controls) decreased. Conditioning stimulation in the upper arm did not affect sensitivity to test stimuli in the infraspinatus muscle. In conclusion, patients with whiplash associated disorder had increased sensitivity to painful stimulation, reported larger areas of referred pain during the same subjectively painful conditioning stimulation (i.e., lower absolute stimulus intensities), including proximal pain referral which was never seen in controls, indicating aberrant processing of nociceptive input. The perceptual integration of nociceptive stimuli during simultaneous stimulation did not differ between groups suggesting that divergence of nociceptive input from the focal pain area leading to excitation of neurones with projected fields in the referred pain area most likely explains referred pain in both groups alike.     

Lesson of the month (2). Angina without 'strangling and anxiety of the breast'

Frequently patients with coronary artery disease (CAD) present with chest pain. Anginal equivalents such as dyspnoea and fatigue, or radiation of pain to the neck, jaw and arm, are also well described. Absence of chest pain with chronic left arm and neck pain is more unusual but demonstrates the heterogeneity of presentation. CAD should be considered in those anginal equivalents in the absence of 'strangling and anxiety of the breast'.     

自制软枕预防乳腺癌术后患侧上肢淋巴水肿的效果观察

目的:应用自制软枕,预防或减少乳腺癌术后患侧上肢淋巴水肿的发生.方法:采用数字表随机分组,将临床诊断且经病理证实的乳腺癌行乳腺癌改良根治术患者70例分为实验组和观察组各35例.实验组术后给予自制软枕抬高患侧上肢,对照组按传统方法护理,比较术侧上臂周径、疼痛和活动情况.结果:实验组有11例术后患侧上臂周径较术前大于1.0 cm(占31.43%),明显低于对照组的20例(占57.14%);实验组发生水肿者的持续天数明显少于对照组(5.45 vs 8.50,P<0.01);实验组术后疼痛天数明显少于对照组(5.09 vs 6.46,P<0.05).结论:使用自制软枕可减少乳腺癌术后患侧上肢淋巴水肿的发生,且可使水肿程度和疼痛程度减轻,患者感觉舒适,具有一定使用价值.     

Evaluation of a new rehabilitation program for postoperative patients with breast cancer

The purpose of the present study was to evaluate the efficacy of a newly designed rehabilitation program for postoperative patients with breast cancer. This was achieved through examinations to clarify the range of motion (ROM) of the shoulder joint, postoperative pain and recovery of activities of daily living (ADL). The ROM of the shoulder joint was evaluated with respect to five items and determinations were carried out five times. Patients were orally questioned four times regarding their pain after surgery, movement-associated chest pain, pain at night and operative wound pain. Evaluation of the ADL after discharge was conducted using a three-level rating method at postoperative week 4 and week 12. A total of 72 patients were studied, comprising 39 who underwent pectoral muscle-conserving mastectomy and 33 who underwent breast-conserving surgery. The arm movement of forward raising showed the greatest decline, followed by lateral raising of the arm. Postoperative time-course changes in internal/external arm rotation, as well as backward arm raising were slight. Comparison of the operative procedures revealed differences only for lateral arm raising at postoperative week 4, while there were no differences in any of the shoulder joint movements. Lowering of the ROM of the shoulder joint was more marked at an earlier time (week 1 to week 2) after surgery, but it was not statistically significant. Pain at night and operative wound pain were prolonged over the period, and reported in postoperative week 1 to week 12 by 3-15% of patients. All ADL items became almost normal in approximately 90% of patients at postoperative week 4. The efficacy of the present rehabilitation program early after surgery was demonstrated in terms of recovery of ADL as well as the ROM of the arm on the affected side.     

The Development of the Negative Pain Thoughts Questionnaire

Background: Cognitive processes play a pivotal role in the perception of pain intensity, pain‐related disability, and response to medical treatments including surgeries. While various measures of dysfunctional pain coping exist in the literature, there is no instrument available to examine such negative cognitions in relation to perceptions of medical treatment in pain patients presenting to a surgical orthopedics practice. Aims: The purpose of this article is to report on the development and preliminary testing of the Negative Pain Thoughts Questionnaire (NPTQ). Methods: The NPTQ is an 11‐item questionnaire assessing cognitions about pain and its treatment in patients presenting to orthopedics surgical practices. It was administered to 2 samples of patients with hand and arm pain seeking medical treatment in a hospital surgical practice. Patients in the second sample also completed a measure of depression and one of disability of hand, arm, and shoulder. Results: The NPTQ was found to be internally consistent, and unidimensional. The NPTQ total score was found to have a moderate to high positive correlation with perceived hand, arm, and shoulder disability, and a moderate positive correlation with depression. In multivariate analyses, high scores on the NPTQ significantly predicted high perceived hand, arm, and shoulder disability, even after controlling for depression. Conclusion: This short and easily administered measure of negative pain thoughts could potentially help surgeons identify at risk patients, and facilitate referrals to cognitive behavioral therapy. This, in turn, may prevent unnecessary surgeries, may decrease healthcare costs, and prevent transition toward costly chronic pain syndrome. ?     

The long-term outcome of arm function after stroke: results of a follow-up study

Purpose: To assess the long-term motor and functional recovery of arm function after stroke. Design: Cohort study. Subjects: Fifty-four patients with a first stroke, who underwent inpatient rehabilitation, were measured early after stroke, after 16 weeks and after 4 years. Measures: Fugl-Meyer Motor Assessment (FM, upper extremity), Action Research Arm Test (ARA), Barthel Index, Arm Function Questionnaire, shoulder pain and range of motion, sensory function, Ashworth Scale and a perceived problem score. Results: Although most of the improvement occurred during the first 16 weeks after stroke, improvement in the FM score continued after 16 weeks in 10 patients. In 13 patients the recovery of arm function only started after 16 weeks. After 4 years a fair to good recovery of arm motor function (FM score 20) was found in 31 patients. Twenty-seven patients had fair to good functional abilities of the hemiplegic arm (ARA 25). Submaximal ARA scores for the unaffected arm were found in 11 patients. Barthel scores 60 were found in 52 patients. Serious shoulder pain persisted in 11 patients. Intact sensory function was found in only 14 patients. It was associated with good motor recovery (FM score 35 in 11 patients). Loss of arm function was perceived as a major problem by 36 patients. Conclusion: This is the first study to investigate the recovery of arm function after stroke over a period of 4 years. It is encouraging to note that even after 16 weeks improvement still occurred in some patients. However, considerable long-term loss of arm function, associated disability and perceived problems were found. There is an obvious need to develop effective treatment methods for hemiplegic arm function.     

The long-term outcome of arm function after stroke: results of a follow-up study

Purpose: To assess the long-term motor and functional recovery of arm function after stroke. Design: Cohort study. Subjects: Fifty-four patients with a first stroke, who underwent inpatient rehabilitation, were measured early after stroke, after 16 weeks and after 4 years. Measures: Fugl-Meyer Motor Assessment (FM, upper extremity), Action Research Arm Test (ARA), Barthel Index, Arm Function Questionnaire, shoulder pain and range of motion, sensory function, Ashworth Scale and a perceived problem score. Results: Although most of the improvement occurred during the first 16 weeks after stroke, improvement in the FM score continued after 16 weeks in 10 patients. In 13 patients the recovery of arm function only started after 16 weeks. After 4 years a fair to good recovery of arm motor function (FM score 20) was found in 31 patients. Twenty-seven patients had fair to good functional abilities of the hemiplegic arm (ARA 25). Submaximal ARA scores for the unaffected arm were found in 11 patients. Barthel scores 60 were found in 52 patients. Serious shoulder pain persisted in 11 patients. Intact sensory function was found in only 14 patients. It was associated with good motor recovery (FM score 35 in 11 patients). Loss of arm function was perceived as a major problem by 36 patients. Conclusion: This is the first study to investigate the recovery of arm function after stroke over a period of 4 years. It is encouraging to note that even after 16 weeks improvement still occurred in some patients. However, considerable long-term loss of arm function, associated disability and perceived problems were found. There is an obvious need to develop effective treatment methods for hemiplegic arm function.     

Kinematics of the contralateral and ipsilateral shoulder: a possible relationship with post-stroke shoulder pain.

OBJECTIVE: Post-stroke shoulder pain is a common phenomenon in hemiplegia and impedes rehabilitation. The aim of this study was to identify a possible relationship between post-stroke shoulder pain, scapula resting position and shoulder motion. METHODS: Shoulder kinematics of 27 patients after stroke (17 men) were compared with 10 healthy age-matched control subjects. Using an electromagnetic tracking device, the kinematics of both the contralateral and ipsilateral (i.e. paretic and non-paretic) arm during active and passive abduction and forward flexion were measured and expressed in Euler angles. RESULTS: Scapular lateral rotation relative to the thorax was increased in patients with post-stroke shoulder pain compared with both patients without post-stroke shoulder pain and control subjects at rest as well as during arm abduction and forward flexion. Additionally, glenohumeral elevation was decreased in patients with post-stroke shoulder pain during passive abduction. No differences were found regarding scapula position (displacement relative to the thorax). CONCLUSION: In patients with post-stroke shoulder pain a particular kinematical shoulder pattern was established, characterized by enhanced scapular lateral rotation and diminished glenohumeral mobility.     

Once an Avoider Always an Avoider? Return of Pain-Related Avoidance After Extinction With Response Prevention

In exposure for chronic pain, avoidance is often forbidden (extinction with response prevention; RPE) to prevent misattributions of safety. Although exposure is an effective treatment, relapse is common. Little is known about the underlying mechanisms of return of pain-related avoidance. We hypothesized that pain-related avoidance would recover when becoming available again after RPE and after unexpected pain episodes (“reinstatement”), especially when restricting avoidance during RPE (compared to instructing not to use it). In an operant pain-related avoidance conditioning paradigm, healthy volunteers used a robotic arm to perform various arm reaching movements differing in pain-effort trade-off. During acquisition, participants learned to avoid pain by performing more effortful movements. During RPE they only performed the formerly pain-associated movement under extinction, and were either forbidden (Restricted group) or merely instructed (Instructed group) not to perform other movements. One day later, we tested spontaneous recovery and reinstatement of pain-related fear and avoidance with availability of all movements. Results showed that pain-related fear and avoidance re-emerge after RPE, though not to pretreatment levels. The reinstatement manipulation had no additional effect. No group differences were observed. We discuss findings in the context of learning processes in (chronic) pain disability and relapse prevention in chronic pain treatment.Perspective: Using experimental models of relapse, we investigated the return of pain-related avoidance behavior after extinction with response prevention. Findings are potentially informative for clinicians performing exposure treatment with chronic pain patients.