Disputing space-based biases in unilateral complex regional pain syndrome

Abstract

There is some evidence that people with Complex Regional Pain Syndrome (CRPS) show reduced attention to the affected relative to unaffected limb and its surrounding space, resembling hemispatial neglect after brain injury. These neuropsychological symptoms could be related to central mechanisms of pathological pain and contribute to its clinical manifestation. However, the existing evidence of changes in spatial cognition is limited and often inconsistent. We examined visuospatial attention, the mental representation of space, and spatially-defined motor function in 54 people with unilateral upper-limb CRPS and 22 pain-free controls. Contrary to our hypotheses and previous evidence, individuals with CRPS did not show any systematic spatial biases in visuospatial attention to or representation of the side of space corresponding to their affected limb (relative to the unaffected side). We found very little evidence of directional slowing of movements towards the affected relative to unaffected side that would be consistent with motor neglect. People with CRPS were, however, slower than controls to initiate and execute movements with both their affected and unaffected hands, which suggests disrupted central motor networks. Finally, we found no evidence of any clinical relevance of changes in spatial cognition because there were no relationships between the magnitude of spatial biases and the severity of pain or other CRPS symptoms. The results did reveal potential relationships between CRPS pain and symptom severity, subjective body perception disturbance, and extent of motor impairment, which would support treatments focused on normalizing body representation and improving motor function. Our findings suggest that previously reported spatial biases in CRPS might have been overstated.

Characterising sensorimotor adaptation in Complex Regional Pain Syndrome

“…This, as well as other recent findings that people with CRPS showed no spatial attention bias (e.g. De Paepe et al, 2020; Filbrich et al, 2017; Halicka, Vittersø, et al, 2020a; Ten Brink, Halicka, Vittersø, Keogh, & Bultitude, 2020), leads us to conclude that prism adaptation is ineffective because spatial representation and attention do not underlie the physical manifestations of CRPS. Nonetheless, our findings that sensorimotor adaptation is no different to – perhaps even better than – normal suggests that sensorimotor processing could be exploited for rehabilitation.…”

Prism adaptation treatment for upper-limb Complex Regional Pain Syndrome: a double-blind randomized controlled trial

“…(b) In the protocol, when specifying selection of potential predictors we planned to prioritize those factors on which participants with CRPS significantly differed from pain-free participants at baseline (research question 5; [34]). However, they showed no differences on the tests of neuropsychological functions (results reported elsewhere [32]). Thus, we instead included all primary and secondary outcomes as potential explanatory variables.…”

“…The transient sensorimotor incongruence introduced by wearing prisms is thought to provide an error signal that triggers normalisation of body representation and sensorimotor integration [9,100]. On average, our participants showed balanced distributions of spatial attention and spatial representations, no systematic slowing of movements directed towards the affected side, and unimpaired laterality recognition of images of affected hands at baseline (see Table 2 and [32]). Cognitive after-effects of PA have been shown to depend on baseline spatial bias [14,29,44].…”

“…Participants with CRPS were primarily recruited for the current RCT of PA treatment (questions 1-4), but we also collected measures of spatial cognition, motor control, and body representation at baseline (RS1) for comparison with pain-free controls and correlational analysis with clinical signs of CRPS (question 5; data reported elsewhere [32]).…”

The Role of Nonmedical Therapeutic Approaches in the Rehabilitation of Complex Regional Pain Syndrome

“…Research has also begun to explore neurophysiological approaches. Evidence from a number of studies suggests a structural reorganisation of the brain is associated with chronic pain [70,71]. Such reorganisation has been recognised in CRPS and its association with pain experience is supported by studies of how CRPS patients represent and attend to their affected limb [72,73] and of the consequent impacts of visual neglect and emotional changes about the painful limb on motor and autonomic function [74][75][76].…”