Image © monkeybusinessimages
Complex regional pain syndrome [CRPS] is a chronic pain syndrome of unknown cause. It usually affects the lower or upper limbs after an injury, accident or surgery, which is why it often appears in a schedule of damages in a medico-legal claim. It is accompanied by a set of variable symptoms, which include allodynia [normal sensation is experienced as painful], vasomotor [vascular], sudomotor [sweating], and motor [abnormal movements] changes. It has traditionally been divided into Type 1 [the result of a soft tissue injury and previously termed reflex sympathetic dystrophy] and Type 2 [the result of nerve damage-so-called neuropathic pain, and previously called causalgia]. These criteria have been more systematically defined in the Budapest Criteria [see Box 1]
CRPS is uncommon and can occur at any age with the average age at diagnosis being 42. It is three times more common in females than males and is increasingly being seen in medico-legal settings. There is also some evidence that it is being over diagnosed¹. The Royal College of Physicians published a document in 2012 describing the clinical features, treatment and prognosis of the disorder.²
In the last few years however there have been major criticisms of the disorder. I will divide these criticisms into three categories. First, the diagnostic criteria are very non-specific, because there is no gold standard laboratory or imaging test to establish it. As a consequence the diagnosis lacks what doctors
refer to as “validity and reliability,” and this leads in turn to very poor levels of inter-observer agreement among doctors. A good example of this was seen at a tertiary care pain clinic in Toronto, Canada, where three quarters of patients referred with a diagnosis of CRPS [I or II] by a primary care doctor or specialist did not fulfil the Budapest clinical diagnostic criteria³. This problem was also demonstrated recently in a study of patients with CRPS who presented in a medico-legal setting: in two fifths of cases there was lack of agreement between the examining clinicians about the diagnosis⁴.
These shortcomings of the diagnostic criteria were recently summarised in a systematic review from the USA¹:
• The use of diagnosis CRPS I has become a catch-all phase with serious questions on whether it exist at all; this has led to an extraordinary number of poorly defined diagnostic criteria.
• The overdiagnosis of CRPS has led to overzealous use of pain medications, including narcotics.
• The diagnostic criteria for CRPS I, and therefore the diagnosis itself, is unreliable
• The underlying pathophysiology of the signs and symptoms of CPRS I are not biologically plausible
• There are no consistent laboratory or imaging testing available
• The signs and symptoms of CRPS I fluctuate over time without a medical explanation, and most studies are derived from statistical analysis with little consideration to required sample size, i.e. power calculations
Second, there is evidence that the signs and symptoms of CRPS can be reproduced by immobilization. After a limb fracture and/or surgery with subsequent cast immobilization, a substantial proportion of patients will exhibit at least one of the signs and symptoms of CRPS Type 1, including movement-induced pain, sensitization to a variety of mechanical and thermal stimuli, oedema [swelling], vasomotor instability and joint stiffness. It has even been suggested by a Dutch expert that the clinical manifestations of CRPS can be reproduced by a combination of fear and immobilization.⁵ Ek has recommended that the term CRPS should be renamed post–immobilsation syndrome or PIS, and has argued that this would in turn encourage the patient to engage in normal behaviour i.e. mobilization. Significantly, there is evidence that this treatment, recently described as “pain exposure” can be helpful in these patients.⁶
Finally, there is the vexed question of psychological contribution to the pain complaints. It was reported in the RCP document that “CRPS is not associated with a history of pain-preceding psychological problems, or with somatisation.”² However, evidence is accumulating to suggest that there is a subset of patients who are diagnosed with CRPS who have a vulnerability to develop so-called “functional” i.e. non-organic syndromes. These include a group of overlapping disorders such as fibromyalgia, irritable bowel syndrome, non- cardiac [muscular] chest pains, tension headaches, migraine etc. Because medical records [often dating from birth] are made available to doctors writing medicolegal reports, it is often possible to examine the longitudinal health record for evidence of previous pain syndromes. It has recently been shown for example that a previous diagnosis of fibromyalgia is a predictor of CRPS after a distal radius fracture, and that migraine is also over- represented in the histories of these patients.
In a study carried out in a medico-legal setting, 40% of patients with CRPS involved in litigation were found to have experienced previous episodes of two or more functional syndromes such as IBS and migraine⁴. This suggests that a subgroup of patients designated CRPS have a pain vulnerability or pain sensitivity. There is also an increased likelihood that these patients have evidence of a current somatic symptom disorder or SSD, defined below:
In these cases the patient has usually responded to an injury/accident with an exaggerated sense of fear and alarm [so-called “catastrophic thinking”] as well as fear-avoidance behaviour i.e. immobility of a limb or part of a limb which has contributed to the condition becoming chronic.
Evidence that the patient with CRPS has a SSD [or what used to be called a somatoform disorder] is greatly assisted therefore by the expert providing a chronology documenting a longitudinal health record. In some cases this will reveal past histories of multiple recurrent episodes of pain [some with “functional” syndromes co-occurring with recurrent low back, neck and other musculoskeletal pains], which may be punctuated by episodes of depression, anxiety and occupational stress. Alcohol and/or drug misuse may also be detected, and provide evidence of the patient’s coping resources, which may be compromised by repeated episodes of pain.
For example, patients with emotionally unstable personalities are habitually alarmed by the pain experience and may respond to it by repeatedly and impulsively admitting themselves to A and E departments. An example of the importance of the longitudinal health record was made clear in a recent judgment in a CRPS case with SSD⁷.
The influence of iatrogenic factors and the nocebo effect cannot be under estimated in these cases. These patients often end up being prescribed opiates and may be informed by a clinician that the pain “might spread to the other limb.” In patients who are vulnerable to and have a heightened awareness of pain complaints with high levels of illness worry such comments may become self-fulfilling.
Treatment
There is a lack of consensus about treatment of CRPS. Deborah Bean, a psychologist from New Zealand, has carried out a number of studies showing that anxiety, pain-related fear and disability are associated with poor outcomes in patients with CRPS.⁸ Her findings support the theory that CRPS represents an aberrant protective response to perceived threat of tissue injury, and support the view that the most appropriate therapeutic and cost effective intervention is physical activity. This should be instigated early and supervised by clinicians with experience of treating patients with a combination of physical and psychological problems.
Conclusions
CRPS is a heterogeneous condition with multiple causes. Evidence is accruing to suggest that psychosocial factors are more important in the maintenance of the disorder than was previously considered. There is a range of opinion about the causes, maintaining factors and optimum treatment approaches, and there is evidence that in some cases the disorders are somatoform in nature. Dogmatic approaches to the clinical dilemmas posed by these patients are ill advised, and experts should always consider a range of opinion. Diagnoses should be influenced not only by an awareness of pre-existing medical history [especially recurrent pain syndromes, which may reflect a vulnerability shaped by genetic andenvironmentalfactors]butalsobyanawareness of those psychological factors that are maintaining the current pain complaints and behaviour.
References
¹ Borchers A Gerswhin W. The clinical relevance of complex regional pain syndrome Type 1;The Emperor’s New Clothes. Autoimmunity Reviews 2017; 16:22-33.
² Royal College of Physicians. Complex regional pain syndrome in adults. UK guidelines for diagnosis, referral and management in primary and secondary care. London, May 2012.
³ Mailis-Gagnon A, Lakha S, Allen M et al. Characteristics of complex regional pain syndrome in patients referred to a tertiary pain clinic by community physicians, assessed by the Budapest clinical diagnostic criteria. Pain Med 2014; 15:1965-74.
⁴ Bass C Yates G. Complex regional pain syndrome in a medicolegal setting: high rates of somatoform disorder, opiate use and diagnostic uncertainty. Med Sci Law 2018; 58:147-55.
⁵ Ek J. Complex Regional Pain Syndrome type 1 does not exist. Can it be a normal reaction after immobilization?) BMJ 2014; 348:g2631
⁶ den Hollander M, Goossens M, de Jong J et al. Expose or protect? A randomized controlled trial of exposure in vivo vs pain- contingent treatment as usual in patients with complex regional pain syndrome type 1. Pain 2016; 157:2318-29., 2016
⁷ Ruffell v Lovatt HHJ Hughes QC 4 April 2018
⁸ Bean D Johnson M Heiss-Dunlop W et al. Do psychological factors influence recovery from CRPS Type 1? A prospective study. Pain 2015; 156:2310-8.
Published by: