The present study sought to describe a sample of children diagnosed with CRPS using well-validated and accepted diagnostic criteria and to compare this sample with children with other pain conditions in terms of demographic, pain, physical functioning and psychological characteristics using standardized, validated measures. Results reveal that the vast majority of children with CRPS are female, with an even greater sex disparity in this diagnostic group compared with other pediatric chronic pain conditions. The previously documented lower extremity preponderance in pediatric CRPS (6
) was confirmed in the present study. Relative to other chronic pain conditions seen at our tertiary care pediatric pain clinic, children with CRPS have shorter mean pain duration at the time of referral to a tertiary care pain clinic and report higher current pain severity. It is notable, however, that all groups in the present study had a mean pain duration of >1 year at the time of evaluation in this clinic, underscoring both the complexity of this sample and the use of tertiary pediatric chronic pain clinics as a ‘last resort’ referral after failure to improve with more standard routes of care.
Children with CRPS are more likely to have tried physical therapy and anesthetic block procedures before their initial multidisciplinary evaluation than children with other pain conditions, but are less likely to have pursued psychological treatment compared with children with abdominal pain. It is possible that the longer time since pain onset for the abdominal pain group compared with the CRPS group accounts for their increased previous exposure to psychological treatment. The difference in current reported pain severity between the CRPS group and other diagnostic groups is particularly striking, given that ratings were taken at rest and CRPS pain is exacerbated by touch and movement.
Partially confirming the study hypotheses, differences between CRPS and other pain conditions were noted in levels of pain-related disability, with the CRPS group reporting more global functional disability than the other diagnostic groups. Similarly, these children reported more widespread pain and other symptom complaints on the CSI. Because pediatric CRPS typically involves a lower extremity, thus inhibiting ambulation, it is not surprising that daily functional abilities are more impaired in this group. The greater number of somatic symptoms may be accounted for by the fact that CRPS is considered to entail central pain sensitization and thus may lead to pain and hyperesthesia in other areas of the body over time. However, the alternative explanation, that children with CRPS have heightened levels of hypervigilance to physiological or somatic experiences, cannot be ruled out and merits further investigation (54
In terms of school attendance, the opposite pattern emerged. Children with CRPS reported fewer missed school days than children with headache or abdominal pain, suggesting that even in the face of greater physical disability, children with CRPS as a group report comparatively less school impairment. This is somewhat surprising because CRPS is typically characterized by constant pain whereas headache and abdominal pain may be intermittent. Perhaps some children with constant pain find ways to function in spite of their ongoing pain, whereas children with episodic pain are more debilitated by their pain episodes. More research is required in this area to understand these patterns.
Contrary to the hypothesis, at the group level, children with CRPS reported no greater anxiety or depressive symptoms than children with other pain conditions, with self-reported symptoms within normal limits compared with standardized scores based on normative samples. In some respects, the CRPS group appears to be less psychologically impaired than children with other types of chronic pain. Relative to other diagnostic groups in the sample, the CRPS group was less likely to use passive coping strategies (eg, pain catastrophizing), which have been demonstrated to be less effective ways of coping with pain (42
). The finding that these children, on average, do not manifest clinically significant psychological distress is consistent with previous research of children with CRPS using standardized assessment tools (36
), and in opposition to studies relying solely on interview and case study methodologies that report elevated levels of psychological impairment (25
). It is clear that group means do not capture the individual variation that undoubtedly exists within the pediatric CRPS population. Clinical experience suggests that some children with CRPS do, in fact, present with elevated symptoms of depression and anxiety, similar to children with other chronic pain conditions, whereas other children may demonstrate psychological resilience in the face of the challenges of chronic pain. In the setting of a chronic pain clinic where children present with a mean pain duration of one to two years, it is not possible to determine whether this distress, when present, is a cause or consequence of the pain experience, or simply a coexisting condition. However, these group-level findings provide an important balance against previous case studies and clinical observations that imply a primarily psychological etiology in patients with CRPS. It should be noted that the absence of significant psychological differences between pediatric CRPS patients and patients with other chronic pain conditions in the present study can be interpreted with more confidence than in previous studies due to the relatively large sample size available and the application of rigorous CRPS diagnostic criteria. The current study would have been able to detect a difference between CRPS patients and other pain groups reflecting even a small to moderate effect size (d=0.40) with a statistical power of 0.80 if such differences existed.
Recent work involving adult CRPS patients suggests that the role of psychological factors in the condition may be linked to physiological processes (55
). Although results of the current study indicate that children with CRPS may not experience a unique degree of psychological distress compared with children with other chronic pain conditions, this does not necessarily rule out a possible impact of emotional distress on CRPS development, potentially via links between distress and adrenergic mechanisms contributing to CRPS (55
). For example, Harden et al (2
) found that in adults, greater increases in anxiety and depression in the four weeks following total knee arthroplasty predicted greater levels of CRPS symptoms up to 12 months following surgery. In a daily diary study of adults with CRPS, Feldman et al (56
) suggest that a transactional relationship exists among pain, emotional distress and social support, such that pain and emotional distress (depression, anger, anxiety) exacerbate one another, with social support exerting a protective buffering influence. In a study of brain anatomy using magnetic resonance imaging techniques, Geha et al (57
) detected abnormal gray-white matter interactions that could account for both pain and emotional reactions in adults with CRPS. Collectively, these studies suggest that psychological factors are frequently involved in the experience of CRPS among adult patients; however, their role is likely to be complex and is not yet fully understood. Clearly, more research is needed to understand these associations in the pediatric population.
Overall, the findings of the present study support the view that pediatric CRPS is a complex condition that can be best understood and treated through a biopsychosocial framework. These results do not support assertions in some previous reports that the psychological aspects of CRPS are more pronounced than those of other chronic pediatric pain disorders. Many children presenting for tertiary evaluation of CRPS report having previously been told that the condition is due to stress, or is ‘all in their heads’. While it is likely that psychological factors in the child and family do influence the expression of CRPS in terms of its course, severity and/or response to treatment, assuming that children fit a particular personality type or have significant psychiatric involvement in the presentation of their pain condition based on a CRPS diagnosis alone is unfounded and may be detrimental to children and their families seeking to understand an often difficult and confusing diagnosis. Certainly, the identification and treatment of psychological concomitants, such as symptoms of depression or anxiety, and of interpersonal factors that can influence the course of the disorder, such as family dynamics and parental responses to pain behaviours, are important goals in managing pediatric CRPS. However, it is crucial to recognize that although the symptom pictures may overlap, true (ie, properly diagnosed) CRPS should not be presumed to be a conversion reaction or other psychosomatic disorder but should be viewed as a complex biopsychosocial phenomenon. Consequently, treatment should entail coordinated interdisciplinary efforts that address the biological, physical and psychosocial aspects and sequelae of this complex condition.
The findings of the present study must be evaluated in light of several limitations. First, the study was retrospective and cross-sectional in design. The tertiary clinic-based sample may not be fully representative of the larger population of all children who experience chronic pain. The study is further limited by reliance on self-report assessments of psychological functioning at a single time point, which may be open to social desirability influences, particularly in the setting of a first-time clinical evaluation (43
). Although children with CRPS were classified using specific diagnostic criteria, inclusion in the comparison groups did not require adherence to strict diagnostic criteria; therefore, the comparison groups may represent heterogenous conditions with a shared pain location. Finally, it is important to highlight that the diagnostic criteria for CRPS were developed for adult patient populations and were applied to a pediatric sample in the present study because no pediatric criteria have been developed. These criteria may be overly stringent for use with children.
Further work is needed to advance our understanding of pediatric CRPS. Prospective longitudinal studies, particularly those that capture a wide sample of children before some develop CRPS, could provide valuable additional insight into the interplay and causal relations of psychological and biological influences on the condition over time. Future studies should include multiple methods of assessing psychological, behavioural and physical functioning both within the child with pain and in the systems (family, school, etc) comprising the child’s environment.
Clinically, much remains unknown regarding this complex chronic pain condition. However, it is hoped that studies such as this will lead to the thorough and accurate assessment and treatment of CRPS by clarifying to medical and mental health practitioners alike that CRPS is a complex chronic pain experience, the maintenance and expression of which are influenced by many individual and environmental factors. Careful diagnosis and evaluation of children with symptoms of CRPS and the provision of treatments to address the multiple biopsychosocial facets of this complex condition are crucial tasks facing pediatric psychologists and other health care providers who encounter this challenging pain condition.