Two-point discrimination and judgment of laterality in individuals with chronic unilateral non-traumatic shoulder pain

Tactile acuity, left/right judgment performance, motor imagery ability, and pressure-pain threshold in patients with chronic rotator cuff-related shoulder pain: a cross-sectional case-control study

BACKGROUND

Chronic pain can alter cortical pain representation, and tests like Two-Point Discrimination Test (TPDT), Left/Right Judgment Task (LRJT), motor imagery, and Pressure-Pain Threshold (PPT) can assess these changes. However, their applicability to all pain mechanisms is uncertain.

OBJECTIVE

To compare the TPDT, LRJT, motor imagery ability, and PPT of chronic rotator cuff-related shoulder pain (C-RCRSP) patients with asymptomatic and pain-free controls.

METHODS

Forty-eight C-RCRSP patients and 45 pain-free controls were assessed using a caliper for TPDT and the Recognize® application for LRJT. Motor ability, PPT, physical function, fear avoidance, pain catastrophizing, and Central Sensitization Inventory (CSI) were also evaluated. As part of the subgroup analysis, C-RCRSP patients were divided into two groups based on their CSI (≥40, n = 19; <40, n = 29).

RESULTS

C-RCRSP patients demonstrated higher TPDT thresholds [acromion (F = 5.41, p = 0.001) and deltoid (F = 26.67, p < 0.001)] but no significant differences in LRJT performance [recognition accuracy (F = 2.47, p = 0.063) and response time (F = 0.98, p = 0.414)] than pain-free controls in both shoulder joints. C-RCRSP patients had poorer motor imagery abilities (p < 0.001). The deltoid region PPT differed significantly between the groups (F = 17.45, p < 0.001), but it was not significant for the tibialis anterior region (F = 1.16, p = 0.33). C-RCRSP patients with a CSI≥40 reported higher night pain, reduced shoulder range of motion, slower response times, poorer motor imagery ability, and higher scores on pain-related questionnaires compared to those with a CSI<40 (p = 0.043-<0.001).

CONCLUSION

C-RCRSP patients demonstrated poorer tactile acuity, mechanical sensitivity, and motor imagery ability especially in those with central sensitization, which should be considered in treatment planning.

Implicit Motor Imagery for Chronic Pelvic Pain: A Cross-Sectional Case-Control Study

Implicit motor imagery (IMI), with an image laterality discrimination (LD) task, has been proposed as a useful therapeutic tool to restore body schema in patients with chronic pelvic pain (CPP). The aim of this study was to analyse the existence of differences between patients with CPP and healthy individuals in order to justify the use of IMI. An observational, cross-sectional study with non-probabilistic sampling was designed as a one-to-one matched case-control study. Through a web link designed for this purpose, a total of 40 abdominoperineal images were shown to 130 participants during the laterality task. Outcome measures were pain intensity (visual analogue scale, VAS), accuracy, response time (RT), and CPPQ-Mohedo score (Chronic Pelvic Pain Questionnaire-Mohedo). This was an observational, cross-sectional study with a total of 64 CPP patients and 66 healthy individuals. The comparative analysis between groups revealed significant differences in accuracy, CPPQ-Mohedo and VAS (p < 0.001), but not in RT; in patients with CPP, accuracy was correlated with a lower CPPQ-Mohedo score and RT and, the greater the pain intensity, the higher the CPPQ-Mohedo score and RT, and the lower the accuracy. In the LD task, the patients with CPP made more mistakes than the healthy individuals. IMI could be a useful and complementary tool in the therapeutic approach for patients with CPP.

The sensorimotor theory of pathological pain revisited

Harris (1999) proposed that pain can arise in the absence of tissue damage because changes in the cortical representation of the painful body part lead to incongruences between motor intention and sensory feedback. This idea, subsequently termed the sensorimotor theory of pain, has formed the basis for novel treatments for pathological pain. Here we review the evidence that people with pathological pain have changes to processes contributing to sensorimotor function: motor function, sensory feedback, cognitive representations of the body and its surrounding space, multisensory processing, and sensorimotor integration. Changes to sensorimotor processing are most evident in the form of motor deficits, sensory changes, and body representations distortions, and for Complex Regional Pain Syndrome (CRPS), fibromyalgia, and low back pain. Many sensorimotor changes are related to cortical processing, pain, and other clinical characteristics. However, there is very limited evidence that changes in sensorimotor processing actually lead to pain. We therefore propose that the theory is more appropriate for understanding why pain persists rather than how it arises.