This is a summary of a recent review of Complex Regional Pain Syndrome by Shim, Halle, and Shekane, of the Department of Anesthesiology at the Mount Sinai West and St. Luke’s Hospitals, published in the British Journal of Anaethesia.
Complex Regional Pain Syndrome (CRPS) has a profound effect on individual functioning, often with equally profound psychological effects. It is a life-changing rare complication, usually the result of some upper extremity high-energy trauma with (cf. causalgia) or, more commonly, without (cf. reflex sympathetic dystrophy) nerve injury and seems to affect women more commonly than men (Ott and Maihofner, 2018; Kim et al, 2018).
More susceptible:
- distal injury (rather than proximal)
- antebrachial fractures of upper extremity
- intraarticular injuries
- high energy injury
- severe fracture
- prolonged general anaesthesia (rather than regional block)
- surgical fixation
- rheumatism
The clinician will distinguish this complex from other regional pain syndromes because of the presence of the following features:
- autonomic dysfunction
- persistent regional inflammatory changes
- manifestations irreducible to a single dermatome
Its common presenting features often include:
- allodynia
- hyperalgesia
- skin temperature changes
- oedema
The current diagnostic standard is known as the Budapest Criteria (Urits, et al., 2018) and response to treatment can also be tracked with the CRPS Severity Score or CSS (Harden, et al., 2010).
The condition presents a significant therapeutic challenge requiring a multidisciplinary and symptomatic approach, including physical and psychological therapies supplemented by neuropathic pain and anti-inflammatory medications and interventional procedures such as spinal cord stimulation (SCS) and dorsal root ganglion (DRG) stimulation. Of the physical therapies, graded motor imagery (GMI) and mirror therapy seem to offer the most potential.
Medication
- gabapentin: reduced pain, improved sleep
- amitriptyline: reduced pain, improved sleep
- carbamazepine: reduced pain
- NSAIDs: mixed results
- steroids:
- short-term (up to 2 months), oral use: start prednisolone at 0.5 mg/kg daily and taper
- (intrathecal steroids ineffective)
Intervention/s
- sympathetic nerve block (SNB): further studies needed but may be worth offering to the patient
- spinal cord stimulation (SCS): reduced pain, improved quality of life
- DRG stimulation: greater reduction in pain cf. SCS at 3 and 12 months follow-up
Protective?
- 500 – 1000 mg oral vitamin C daily for 50 days
Historically, the condition presented in association with events of multi-trauma, such as the American Civil War, characterised, according to Dr Silas Weir Mitchell, in 1864, of patient complaints of “severe burning pain associated with shinning red skin’, which by 1972 he termed causalgia to refer to “pain in excess of inciting injury.” Almost a century later, 1946 in Massachusetts, James A. Evans described a similarly intense suffering associated with abnormalities of the sympathetic nervous system (SNS) that he designated reflex sympathetic dystrophy. Fifty years later, in 1994, the term Complex Regional Pain Syndrome (CRPS) was adopted.¹
Pathophysiology of CRPS is characterised but not definitively and involves a combination of:
- nervous system sensitisation: lowering of the depolarisation threshold in local and regional tissue
- autonomic dysfunction: persistent Aδ and C afferent neuronal firing overwhelms and conflates the sympathetic and peripheral nociceptive nervous pathways
- inflammation: neuroinflammatory mediators like TNFa and PGE2 implicated, among many others
Electron microscopy examination has demonstrated significant degeneration of Aα nerve fibres and sparing of Aδ fibres, in CRPS. In contrast to lowering of threshold and increased nociceptive dorsal horn firing, somatosensory cortical neural representation is diminished, suggesting a reduced cortical inhibition upon the spinal cord of the involved neural pathways. If sustained, this pathophysiology can lead also to motor dysfunction (reduced digital flexion accompanied by dystonia), impaired recognition, and even neglect.
Autonomic Dysregulation
Systemically, patients initially have reduced circulating noradrenaline (NAd) levels but, in time, because of increased peripheral catecholamine sensitivity (up-regulation of catecholamine receptors, for instance) patients with CRPS have high circulating catecholamine levels causing the cold (vasoconstriction), clammy (hyperhidrosis) skin. More broadly still, associations with a psychological stressed states, such as Post-traumatic Stress Disorder (PTSD), further invoke the implication of catecholamine excess.
Immunologic
Substance P and other proinflammatory neuropeptides cause the release of inflammatory cytokines such as TNFα, IL-1β, IL-6, and nerve growth factor (NGF) which in the acute stages cause tissue oedema (increased vascular ability) and warmth (vasodilatation).
There is also some genetic susceptibility for earlier onset and higher incidence of disease.
Reference
Shim, H. et al. (2019) Complex regional pain syndrome: a narrative review for the practicing clinician. British Journal of Anaesthesia. doi: 10.1016/j.bja.2019.03.030 [Online]
Other Works Cited
- Harden RN, Bruehl S, Perez RS, et al. Development of a severity score for CRPS. Pain 2010; 151: 870e6
- Kim H, Lee CH, Kim SH, Kim YD. Epidemiology of complex regional pain syndrome in Korea: an electronic population health data study. PLoS One 2018; 13, e0198147
- Ott S, Maihofner C. Signs and symptoms in 1,043 patients with complex regional pain syndrome. J Pain 2018; 19:599e611
- Urits I, Shen AH, Jones MR, Viswanath O, Kaye AD. Complex regional pain syndrome, current concepts and treatment options. Curr Pain Headache Rep 2018; 22: 10.
Further Reading
- Bharwani et al., Complex regional pain syndrome: diagnosis and treatment. BJA Education 2017; 0 (0): 1–7.
- Which treatments are effective for the treatment of complex regional pain syndrome in adults? – Cochrane
- Physiotherapy for pain and disability in adults with complex regional pain syndrome (CRPS) types I and II – Cochrane
- Local anaesthetic sympathetic blockade for complex regional pain syndrome – Cochrane
Complex Regional Pain Syndrome synonyms
- Sudeck’s atrophy
- sympathetically mediated pain
- sympathetically independent pain
