Predictors of Self-Reported Neglect-like Symptoms and Involuntary Movements in Complex Regional Pain Syndrome Compared to Other Chronic Limb Pain Conditions

OBJECTIVE: In addition to pain, people with complex regional pain syndrome (CRPS) often report inattention to and disengagement from their affected limb (i.e., "neglect-like symptoms"). Understanding how these symptoms relate to other characteristics of CRPS, and chronic pain generally, could provide insights for preventing and treating CRPS. METHODS: We administered an online survey to people who received a diagnosis of CRPS (n = 335) and other chronic limb pain (n = 407). Neglect-like symptoms were assessed using the Neurobehavioral questionnaire. RESULTS: A principal component analysis identified two components: motor and cognitive neglect-like symptoms, and involuntary movements. Internal consistency of the components was acceptable. We conducted regression analyses with these as outcomes. Having CRPS, a painful lower limb, higher pain intensity, and somatic symptoms were associated with more motor and cognitive neglect-like symptoms. Having CRPS, higher pain intensity, depression, and somatic symptoms were associated with more involuntary movements. Age, gender, anxiety, disease duration, hours of pain per day, affected side, whether the limb was the most painful body part, and number of pain-related medical diagnoses were no predictors. Finally, motor and cognitive neglect-like symptoms were related to tremor; and involuntary movements to changes in skin color, swelling, sweating, toenails, weakness, and tremor. CONCLUSIONS: This study confirms the specificity of inattention to and disengagement from the affected limb in CRPS, independent of other factors. Furthermore, two components of the Neurobehavioral questionnaire were disentangled: motor and cognitive neglect-like symptoms, and involuntary movements. Results could potentially help clinicians to better assess neglect-like symptoms in chronic pain

Validation of the Leiden Visual Sensitivity Scale and Visual Discomfort Scale in Chronic Pain Conditions

Discomfort provoked by normally innocuous visual stimuli has been reported by people with chronic pain. Visual discomfort may be higher in pain conditions in which central sensitization is implicated, such as Complex Regional Pain Syndrome (CRPS) and fibromyalgia. In an online study, we validated the Leiden Visual Sensitivity Scale (L-VISS) and Visual Discomfort Scale (VDS) in people with CRPS (n = 57), fibromyalgia (n = 75), and general chronic pain (n = 53); investigated whether these groups and pain-free controls (n = 125) differed in visual discomfort; and evaluated the effect of age. The L-VISS and VDS had good internal consistency. Both scales were positively related with experimentally induced visual distortions for mid-spatial frequency striped patterns, suggesting good construct validity. The scales were positively related with each other, and dissociated between the pain and pain-free groups in similar ways, suggesting good construct validity. There was no relationship between age and L-VISS scores and a small negative relationship between age and VDS scores. Visual discomfort was highest in the fibromyalgia group, followed by the CRPS group. This research confirms the utility of the L-VISS and VDS for measuring visual sensitivity in chronic pain and adds to evidence that central sensitization is an important mechanism of visual discomfort

Gaze data of 4243 participants shows link between leftward and superior attention biases and age

Healthy individuals typically show more attention to the left than to the right (known as pseudoneglect), and to the upper than to the lower visual field (known as altitudinal pseudoneglect). These biases are thought to reflect asymmetries in neural processes. Attention biases have been used to investigate how these neural asymmetries change with age. However, inconsistent results have been reported regarding the presence and direction of age-related effects on horizontal and vertical attention biases. The observed inconsistencies may be due to insensitive measures and small sample sizes, that usually only feature extreme age groups. We investigated whether spatial attention biases, as indexed by gaze position during free viewing of a single image, are influenced by age. We analysed free-viewing data from 4,243 participants aged 5–65 years and found that attention biases shifted to the right and superior directions with increasing age. These findings are consistent with the idea of developing cerebral asymmetries with age and support the hypothesis of the origin of the leftward bias. Age modulations were found only for the first seven fixations, corresponding to the time window in which an absolute leftward bias in free viewing was previously observed. We interpret this as evidence that the horizontal and vertical attention biases are primarily present when orienting attention to a novel stimulus – and that age modulations of attention orienting are not global modulations of spatial attention. Taken together, our results suggest that attention orienting may be modulated by age and that cortical asymmetries may change with age

Ignoring space around a painful limb? No evidence for a body-related visuospatial attention bias in complex regional pain syndrome

Background: Complex Regional Pain Syndrome (CRPS) is a disorder of severe chronic pain in one or more limb(s). People with CRPS report unusual perceptions of the painful limb suggesting altered body representations, as well as difficulty attending to their affected limb (i.e., a ‘neglect-like’ attention bias). Altered body representations and attention in CRPS might be related, however, existing evidence is unclear. We hypothesized that if there were a body-related visuospatial attention bias in CRPS, then any attention bias away from the affected side should be larger for or limited to circumstances when the (impaired) body representation is involved in the task versus when this is not the case. Methods: We included 40 people with CRPS, 40 with other limb pain conditions, and 40 pain-free controls. In half of the people with pain, their upper limb was affected, in the other half their lower limb. We administered computerized tasks of spatial attention, including free viewing of images, shape cancellation, temporal order judgement, and dot-probe. The degree to which different versions of each task involved body representation was manipulated by one or more of the following: (1) presenting stimuli nearer versus further away from the body, (2) using body related versus neutral stimuli, and (3) inducing mental rotation of body parts versus no mental rotation. In addition to perceptual judgements, eye movements were recorded as a sensitive index of spatial attention. Bayesian repeated measures analyses were performed. Results: We found no evidence for a (body-related) visuospatial attention bias in upper limb CRPS. Secondary analyses suggested the presence of a body-related visuospatial attention bias away from the affected side in some participants with lower limb CRPS. Discussion: Our results add to growing evidence that there might be no general visuospatial attention bias away from the affected side in CRPS.</p

Ignoring space around a painful limb? No evidence for a body-related visuospatial attention bias in complex regional pain syndrome

Background Complex Regional Pain Syndrome (CRPS) is a disorder of severe chronic pain in one or more limb(s). People with CRPS report unusual perceptions of the painful limb suggesting altered body representations, as well as difficulty attending to their affected limb (i.e. a 'neglect-like' attention bias). Altered body representations and attention in CRPS might be related, however, existing evidence is unclear. We hypothesized that if there were a body-related visuospatial attention bias in CRPS, then any attention bias away from the affected side should be larger for or limited to circumstances when the (impaired) body representation is involved in the task versus when this is not the case. Methods We included 40 people with CRPS, 40 with other limb pain conditions, and 40 pain-free controls. In half of the people with pain, their upper limb was affected, in the other half their lower limb. We administered computerized tasks of spatial attention, including free viewing of images, shape cancellation, temporal order judgement, and dot-probe. The degree to which different versions of each task involved body representation was manipulated by one or more of the following: (1) presenting stimuli nearer versus further away from the body, (2) using body related versus neutral stimuli, and (3) inducing mental rotation of body parts versus no mental rotation. In addition to perceptual judgements, eye movements were recorded as a sensitive index of spatial attention. Bayesian repeated measures analyses were performed. Results We found no evidence for a (body-related) visuospatial attention bias in upper limb CRPS. Secondary analyses suggested the presence of a body-related visuospatial attention bias away from the affected side in some participants with lower limb CRPS. Discussion Our results add to growing evidence that there might be no general visuospatial attention bias away from the affected side in CRPS

The mobility assessment course: A ready‐to‐use dynamic measure of visuospatial neglect

The Mobility Assessment Course (MAC) is a tool to measure visuospatial neglect in a dynamic fashion. Although the MAC has been shown to dissociate between patients with and without neglect, it remains unclear whether it is applicable in clinical settings. We evaluated the MAC regarding its (1) feasibility as a diagnostic tool as part of standard care, (2) construct validity, and (3) underlying constructs and potential confounders. A consecutive sample of stroke patients admitted to inpatient rehabilitation completed the MAC, shape cancellation, line bisection, and/or Catherine Bergego Scale (CBS) as part of the standard assessment. To assess feasibility, we computed the percentage of patients who completed the MAC. Construct validity was tested by evaluating MAC performance between patients with and without neglect and controls. Finally, a regression analysis was conducted to assess underlying constructs and potential confounders of MAC performance (i.e., level of mobility and lesion side). The MAC was completed by 82% of patients (N = 182/223; of whom 145 completed all tasks). Patients with neglect performed worse on the MAC (indicating more severe neglect) compared to patients without neglect and controls. The MAC had a lower sensitivity and higher specificity than paper-and-pencil tasks and the CBS. Performance on shape cancellation, line bisection, and CBS were predictors of MAC performance. Level of mobility and lesion side did not predict MAC scores, indicating that these factors do not confound its reliability. To conclude, the MAC is an easy-to-implement tool to evaluate neglect in a dynamic manner, which can be administered in addition to conventional paper-and-pencil tasks

Pupil dilation reveals the intensity of touch

Touch is important for many aspects of our daily activities. One of the most important tactile characteristics is its perceived intensity. However, quantifying the intensity of perceived tactile stimulation is not always possible using overt responses. Here, we show that pupil responses can objectively index the intensity of tactile stimulation in the absence of overt participant responses. In Experiment 1 (n = 32), we stimulated three reportedly differentially sensitive body locations (finger, forearm, and calf) with a single tap of a tactor while tracking pupil responses. Tactile stimulation resulted in greater pupil dilation than a baseline without stimulation. Furthermore, pupils dilated more for the more sensitive location (finger) than for the less sensitive location (forearm and calf). In Experiment 2 (n = 20) we extended these findings by manipulating the intensity of the stimulation with three different intensities, here a short vibration, always at the little finger. Again, pupils dilated more when being stimulated at higher intensities as compared to lower intensities. In summary, pupils dilated more for more sensitive parts of the body at constant stimulation intensity and for more intense stimulation at constant location. Taken together, the results show that the intensity of perceived tactile stimulation can be objectively measured with pupil responses - and that such responses are a versatile marker for touch research. Our findings may pave the way for previously impossible objective tests of tactile sensitivity, for example in minimally conscious state patients

Characterising sensorimotor adaptation in Complex Regional Pain Syndrome

It has been suggested that sensorimotor conflict contributes to the maintenance of some pathological pain conditions, implying that there are problems with the adaptation processes that normally resolve such conflict. We tested whether sensorimotor adaptation is impaired in people with Complex Regional Pain Syndrome (CRPS) by characterising their adaption to lateral prismatic shifts in vision. People with unilateral upper-limb CRPS Type I (n = 17), and pain-free individuals (n = 18; matched for age, sex, and handedness) completed prism adaptation with their affected/non-dominant and non-affected/dominant arms. We examined 1) the rate at which participants compensated for the optical shift during prism exposure (i.e., strategic recalibration), 2) endpoint errors made directly after prism adaptation (sensorimotor realignment) and the retention of these errors, and 3) kinematic markers associated with strategic control. Direct comparisons between people with CRPS and controls revealed no evidence of any differences in strategic recalibration, including no evidence for differences in a kinematic marker associated with trial-by-trial changes in movement plans during prism exposure. All participants made significant endpoint errors after prism adaptation exposure, indicative of sensorimotor realignment. Overall, the magnitude of this realignment did not differ between people with CRPS and pain-free controls. However, when endpoint errors were considered separately for each hand, people with CRPS made greater errors (indicating more rather than less realignment) when using their affected hand than their non-affected hand. No such difference was seen in controls. Taken together, these findings provide no evidence of impaired strategic control or sensorimotor realignment in people with CRPS. In contrast, they provide some indication that there could be a greater propensity for sensorimotor realignment in the CRPS-affected arm, consistent with more flexible representations of the body and peripersonal space. Our study challenges an implicit assumption of the theory that sensorimotor conflict might underlie some pathological pain conditions

Dynamic assessment of visual neglect: The Mobility Assessment Course as a diagnostic tool

Introduction: Visual neglect is a frequent disorder following stroke and is often diagnosed by neuropsychological assessment. However, paper-and-pencil tasks have low predictive value as they lack sensitivity to capture neglect in complex, dynamic situations, such as activities of daily living. Aims of the current study were to assess the feasibility of the Mobility Assessment Course (MAC), a visual search multitask, to assess neglect, and its relation with existing neglect tasks. Method: Stroke patients admitted for inpatient rehabilitation and healthy controls were tested with the MAC in different corridors. Participants had to move through a corridor, finding and reporting 24 targets attached to the walls. In addition, the shape cancellation, line bisection, and Catherine Bergego Scale (CBS) were used in order to compare the MAC with existing diagnostic tools for neglect. Results: Administering the MAC was feasible, as 112 of 113 patients completed the MAC with a median duration of 4.09 min. Depending on the corridor where the assessment took place, in 88.5–93.3% of assessments all targets were visible. The number of omissions (total and contralesional) and the asymmetry score (contralesional–ipsilesional omissions) on the MAC as well as collisions and corrections, were higher for patients with neglect than for those without neglect. Depending on the neglect task used, 4.0–18.6% of patients without neglect on neuropsychological tasks or the CBS showed neglect on the MAC. Vice versa, 17.2–29.3% of patients who showed neglect at neuropsychological assessment or the CBS did not do so on the MAC. Finally, a moderate to strong positive relation was seen between neglect at neuropsychological assessment, the CBS, and the MAC. Conclusions: The MAC is an ecological task in which both quantitative and qualitative data on neglect can be collected. In order to assess the presence of neglect and neglect severity in a dynamic way, the MAC could be administered in conjunction with neuropsychological assessment