Normal manual straight ahead pointing in Complex Regional Pain Syndrome

Abstract

There is evidence to suggest that people with Complex Regional Pain Syndrome (CRPS) can have altered body representations and spatial cognition. One way of studying these cognitive functions is through manual straight ahead (MSA) pointing, in which participants are required to point straight ahead of their perceived body midline without visual feedback of the hand. We therefore compared endpoint errors from MSA pointing between people with CRPS (n = 17) and matched controls (n = 18), and examined the effect of the arm used (Side of Body; affected/non-dominant, non-affected/dominant). For all participants, pointing errors were biased towards the hand being used. We found moderate evidence of no difference between Groups on endpoint errors, and moderate evidence of no interaction with Side of Body. The differences in variability between Groups were non-significant/inconclusive. Correlational analyses showed no evidence of a relationship between MSA endpoint errors and clinical parameters (e.g. CRPS severity, duration, pain) or questionnaire measures (e.g. body representation, “neglect-like symptoms”, upper limb disability). This study is consistent with earlier findings of no difference between people with CRPS and controls on MSA endpoint errors, and is the first to provide statistical evidence of similar performance of these two groups. Our results do not support a relationship between clinical or self-reported measures (e.g. “neglect-like symptoms”) and any directional biases in MSA. Our findings may have implications for understanding neurocognitive changes in CRPS.

The characteristics of the implicit body model of the trunk

“…Investigations with patients in chronic upper limb pain have also shown a shift in perceived midline toward the affected side (Reinersmann et al, 2012). In studies comparing healthy participants and patients with CRPS, no significant difference was found in midline perception for tasks where participants pointed ahead with vision obstructed (Kolb et al, 2012;Verfaille et al, 2021;Vittersø et al, 2021) or directed an illuminated dot/rod to their perceived midline in light (Verfaille et al, 2021) and dark conditions (Verfaille et al, 2021;Wittayer et al, 2018). In contrast, participants with CRPS have also demonstrated a significantly larger leftward shift in their perceived midline compared to patients with chronic upper limb pain and healthy controls (Reinersmann et al, 2012).…”

“…The influence of hand dominance may also play a role in this study's observed midline results. When asking participants to point straight ahead of their perceived body midline without visualising their hand, healthy controls made errors toward their dominant side when pointing with their dominant arm, and toward their non-dominant side when pointing with their non-dominant arm ( Vittersø et al, 2021 ). With the majority of participants in the current study right-hand dominant, this may explain the rightward midline bias observed in our study (and also the rightward bias in the majority of body landmarks).…”

“…As with healthy participants, results for patients with chronic pain are variable. Participants with complex regional pain syndrome (CRPS) did not demonstrate any midline deviation when performing a point straight ahead task for midline either blindfolded ( Verfaille et al, 2021 ) or in dark conditions ( Christophe et al, 2016 ), however with eyes closed, another study found participants deviated to the same side as the arm used ( Vittersø et al, 2021 ). With the visual task of stopping an illuminated dot at the perceived midline position, in illuminated conditions, results also demonstrated no midline deviation for patients with CRPS ( Sumitani et al, 2007 ; Uematsu et al, 2009 ; Verfaille et al, 2021 ) and patients with post-herpetic neuralgia ( Uematsu et al, 2009 ).…”

Reduced Visuospatial Attention in Personal Space is Not Limited to the Affected Limb in Complex Regional Pain Syndrome

“…To be able to compare the performance relative to the CRPS-affected versus unaffected side between the CRPS and control groups, we matched the non-dominant side of controls to the affected side of people with CRPS, following the approach used in previous studies. 26 , 30 A G*power 31 sample size calculation to detect a medium effect size ( eta 2 = 0.05) for an interaction between Group and Body Region (see “Statistical analyses” section), with an alpha level of 0.05 and 80% power resulted in a required sample size of 51, with 17 participants per group (UL-CRPS, LL-CRPS, controls). However, we fell slightly short of this recruitment target for the CRPS groups (see “Sample Characteristics” in the “Results” section).…”