Investigating Object Affordance in People with Complex Regional Pain Syndrome: No Alterations in the Automatic Activation of Motor Plans

Complex Regional Pain Syndrome (CRPS) is a condition of chronic pain, predominantly affecting one limb. CRPS is characterised by motor changes including slowed or uncoordinated movements. Cognitive processes that drive movement planning and/or execution might contribute to these changes. We aimed to investigate the potential alterations to such cognitive mechanisms using an 'object affordance' paradigm. Object affordance refers to the observation that viewing an object modulates associated motor responses, presumably due to the automatic activation of a motor plan. We hypothesised that people with CRPS would show reduced object affordance effects for their affected compared to unaffected hand, and compared to pain-free controls. First, we validated an online object affordance task involving button press responses to everyday objects with handles, in pain-free participants (n = 63; Experiment 1). Object affordance was reflected by faster and more accurate responses when the object handle was aligned to the responding hand ("aligned") compared to when the handle was aligned to the other hand ("non-aligned"). These results were similar for the online task as when administered in person. Second, in a case-control study, we administered the online object affordance task to people with CRPS predominantly affecting the upper limb (n = 25), and age-matched pain-free controls (n = 68; Experiment 2). People with CRPS responded faster and more accurately in the aligned versus non-aligned condition (ie, an object affordance effect), both for the affected and unaffected hands. There were no differences to pain-free participants. Therefore, object affordance effects were seen in people with CRPS, providing no evidence for altered motor planning. PERSPECTIVE: This article presents research investigating cognitive processes related to motor planning in Complex Regional Pain Syndrome (CRPS). Using an online object affordance paradigm, validated in pain-free controls, the authors found that people with CRPS showed intact object affordance effects in the affected and unaffected hand, suggesting unaltered motor planning. DATA AVAILABILITY: The experiment materials, data, pre-processing scripts, and analysis scripts can be found via Open Science Framework (https://osf.io/nc825/files/osfstorage).

Neglect-like symptoms and their relationships with other clinical features in people with hand osteoarthritis: An exploratory study

BACKGROUND

Symptomatic hand osteoarthritis (OA) is a debilitating condition. Body schema impairments such as neglect-like symptoms have been previously reported in people with symptomatic hand OA, however, little is known about their clinical importance, or relationships with other clinical features.

OBJECTIVES

The aim of this cross-sectional study was to assess the prevalence of neglect-like symptoms in painful hand OA and their association with measures of depression, pain catastrophising, sleep quality, function, pain interference and pain duration whilst controlling for important covariates.

DESIGN

Secondary analysis of cross-sectional study.

METHODS

Logistic regression with age, sex, and worst pain intensity as covariates were utilised to assess differences between participants with and without neglect-like symptoms.

RESULTS

A total of 121 participants were recruited. Sixty-one percent of participants presented with neglect-like symptoms. Participants with longer pain duration had greater odds of presenting with neglect-like symptoms (OR: 1.10 95%CI: 1.01 to 1.19; p = 0.012). No difference was observed for depression, pain catastrophising, sleep quality, function, or pain interference.

CONCLUSIONS

A large proportion of participants with symptomatic hand OA reported neglect-like symptoms, the presence of which was associated with longer pain duration.

[Neglect-like symptoms after operations on the upper extremities]

BACKGROUND

Neglect-like symptoms (NLS) describe the experience of perceiving a limb as foreign and could be detected in chronic pain disorders as well as after knee joint replacement. The aim of the present study was to find out whether patients with and without NLS after surgery of the upper extremities differ with respect to pain intensity and psychosocial variables and if NLS are associated with chronic postoperative pain (CPSP).

METHODS

In this study 241 patients were interviewed using a validated questionnaire preoperatively as well as 1 day, 4 weeks, 3 months and 6 months postoperatively. Patients with and without NLS were compared using the χ²-test or Mann-Whitney U‑test. The level of significance was adjusted for multiple testing.

RESULTS

The NLS could be found to a slight extent throughout the entire study period. Patients with NLS showed significantly higher maximum pain scores at every measurement time point: average difference (∆ = 3, adjusted p < 0.005), a higher impairment due to pain (∆ = 15, adjusted p < 0.005), more anxiety (∆ = 3, adjusted p < 0.005), depression (∆ = 3, average adjusted p < 0.003) and kinesiophobia (∆ = 4, preoperative not significant, average postoperative adjusted p = 0.004). Preoperatively, more stressful life events (p = 0.002) and higher stress values (p < 0.001) were reported. In patients with CPSP, NLS occurred significantly more often (74%) than in patients without clinically relevant pain (17.5%. p < 0.001).

CONCLUSION

The occurrence of NLS is associated with higher pain scores, more impairment due to pain and a higher psychosocial burden and they are more frequent in patients with CPSP. Further investigations are needed to show if NLS are an independent risk factor for the chronification of pain and if NLS play an independent role in the pathogenesis of pain.