CRPS: A review, by J Field

I found this paper as I rolled around on the internet yesterday:

J Field; Complex Regional Pain Syndrome: a review

J Hand Surg Eur Vol. 2013 Jan 22

"Abstract 

Complex regional pain syndrome, formally known as reflex sympathetic dystrophy, is a poorly understood condition that describes a collection of clinical symptoms and signs occurring in the peripheries most commonly after trauma. Pain is the main problem. It is generally out of proportion to the degree of injury and can be unresponsive to narcotics. In addition joint stiffness, temperature and colour changes, and swelling occur. The diagnosis and treatment are challenging for any clinician and a multidisciplinary approach is often necessary with physiotherapy, occupational therapy, and the pain team. The hand surgeon is involved for two reasons, firstly as the upper limb is the most frequently involved, and secondly because the condition may be a complication of the patient's surgery and result in a much prolonged recovery. This review elucidates the recent advances in the knowledge of the aetiology, classification and treatment of this fascinating condition."

J. Field of Cheltenham General Hospital is listed here as Mr. Jeremy Field, one of the ortho surgeons. 

Here is his CV. Looks like he specializes in hand surgery and has a special interest in CRPS.

I have treated at least three patients that I know of, in my whole life, who I'm pretty sure had this condition, all women, all post-wrist fracture. The first two I encountered as a young hospital therapist, decades ago. I barely knew what I was doing. If they got better it was in spite of me, not because I was able to help them very well. 

The last one was just a few years ago, long after I had established my own practice and knew a great deal more about pain science. She did very well in an outpatient setting. 

Anyway - to the paper, and some delicious excerpts. 

1. "International Association for the Study of Pain (IASP) in 1994 coined the term complex regional pain syndrome (CRPS). CRPS is divided into two types: CRPS type I where there is no obvious nerve damage and CRPS type II where there is identifiable nerve damage (causalgia) (Stanton-Hicks et al., 1995).
"Using the IASP criteria, patients must have con- tinued disproportionate pain and one symptom in three of four categories (sensory, vasomotor, sudomotor, and motor), and one sign in two of the same categories. There must be no other diagnosis that better explains the symptoms and signs." (p.1)

2. "As the symptoms and signs of both types of CRPS are similar the use of the terms ‘high flow’ CRPS (or warm CRPS) and ‘low flow’ (or cold CRPS ) are being used more often. High flow CRPS, describing the hot, painful oedematous extremity, and low flow CRPS the cool, atrophic limb." (p. 2)

Field says, pain is the biggest problem. Described as burning, nagging and throbbing, it combines three categories into one horrible sensory soup: 

"1. hyperalgesia – increased sensitivity to noxious stimuli – i.e. a pin prick causing very severe pain. 2. allodynia – pain provoked by non noxious stimuli– i.e. stroking the skin causing pain. 3. hyperpathia – temporal summation of allodynia – i.e. repeated stroking causing increased pain." (p.2)

Additionally, it is non-dermatomal, unresponsive to narcotics, "out of proportion to the degree of preciptating injury," severe to the point where active movement is avoided and so is contact. Synchiria ("touching the affected limb hurts the other limb"),  hyperacusis (intolerance of ordinary sound levels),

more generally, smudging of somatosensory representational maps, are common features. Vasomotor instability, swelling, and stiffness are big problems. 

"In CRPS even thinking about moving (motor imagery) can itself cause pain and potentially hinder movement (Moseley, 2004, Moseley et al., 2008)."(p.4)

There does not exist any diagnostic test - diagnosis is clinical.

The juiciest part is the aetiology. I love it when people who write papers actually stick their necks out a little bit, dare to say out loud what everyone already thinks anyway, and sign their name to it. 

Field runs through all the precipitating factors that have been identified: trauma, especially fracture, strokes, heart attacks, smoking, hereditary factors, and even no cause. It can occur following surgery for carpal tunnel or Dupuytren's contracture, so patients undergoing these procedures should be made aware of the risk, however slight it may be. 

Altered limb awareness, opposite limb symptoms, symptoms in face or jaw, do NOT mean the condition is caused psychologically. 

Field thinks there are two main causes, inflammatory and neurological, likely related.

"In the early phase of the condition the clinical features of rubor, tumor, calor, dolor and function laesa certainly point towards an inflammatory response." (p.5)

Presence of inflammatory mediators such as tumour necrosis factor, CGRP, interleukin2, and Substance P, might be the result of neurogenic dysregulation, which leads us to the neurologic points he makes, next (the juciest of the juiciness in this paper): 

"The theory of a neurological abnormality in CRPS type I is the more compelling for two reasons. Firstly the symptoms experienced are so like those in CRPS type II, where there is a specific nerve injury. Secondly the bizarre symptoms associated with pain being experienced in other parts of the body are best explained by cortical reorganisation."

"Neuralgic pain associated with CRPS may be explained by damage to small fibre neurons. These thinly myelinated (A-delta) and unmyelinated (C-fibre and sympathetic axons) transmit afferent information from mechanical, thermal and chemical stimuli. They are also responsible for release of vasoactive peptides such as CGRP and substance P, which are present in CRPS. These small fibres are particularly sensitive to injury, and their degeneration often results in pain (Llewelyn et al., 1991). Nerve conduction studies are not sensitive enough to pick up these abnormalities. Histological examination has found C-fibre degeneration, but no myelinated axon damage in limbs amputated for CRPS (Van der Laan et al., 1998). Immunological labelling of axonal markers has confirmed small fibre nerve damage in CRPS (Oaklander et al., 2006). With this small fibre nerve damage come the trophic changes in the skin seen in CRPS (Figure 2). Very similar skin, nail and hair changes occur in small fibre peripheral neuropathies (SFPN)." (p. 5) (my bold.)

There we are, back to C-fibres and all their weird efferent function, trophic supply to tissue being among them. Without the C-fibres, mesodermal targets don't know what to do with themselves. Without C-fibres, blood supply to everything - including nerves themselves, hello? - becomes a bit of a dysregulated mess. 

He goes on to include bone changes as being the plausible result of small fibre damage.

"Bone scan and radiographic changes are attributed to increased osteoclastic activity. Osteoclasts are only bone resorbing at low ph which is when small fibre nociceptors will fire. Small fibre secretions are critical for bone formation and maintenance and bone is significantly influenced by small fibre axonal degeneration (Hukkanen et al., 1993). The pain in long standing or chronic CRPS could be explained by some form of nerve damage as occurs in the long standing pain experienced in post herpetic neuralgia." (p.5) (my bold.)

He goes on to describe various cortical changes that occur due to CRPS, mapping changes chief among them. 

"There is definitely an alteration of perception of the limb in CRPS. Patients pay less attention to the affected limb, have peculiar desires to amputate, and have a mismatch between sensation of the limb and how it looks." (p.6)

Most of the time symptoms resolve but it can take years, and sometimes... the symptoms do not resolve. 

It might recur, but whether it will or won't is kind of debatable. There isn't enough evidence to suggest it's preventable. Treatment is confusing but the best kind is interdisciplinary. Hand therapy is essential. Mirror therapy can be helpful. DMSO cream might be helpful but evidence is small. Oral medication doesn't seem to help a whole lot. Injections don't seem to work. Don't resort to amputating. Watch out for signs: 

"1. pain, but particularly allodynia and hyperalgesia that can be demonstrated. The temporal summa- tion of hyperalgesia is difficult to feign. 

2. trophic changes in skin and nails. 

3. wasting of muscles. 

4. fixed joint contractures. 

5. radiographs showing periarticular osteopaenia –
although not diagnostic a radiograph showing changes is significant." (p.8)

Red flags include: 

"1. excessive swelling – check for excessively tight cuffs or ligature marks further up the limb. 

2. wrapped-up limbs – these may be to accentuate temperature or colour differences, and bad cases of CRPS would never let anything touch the hand. 

3. flexed posture of fingers with no fixed contracture. 

4. Alterations of colour and temperature can be achieved from dependency and immobilisation of
the hand (Singh and Davis, 2006). 

5. Inconsistency of timing and degree of tremors." (p.8)

Reference:

1. M J M de Klaver, M A van Rijn, J Marinus, W Soede, J A P M de Laat, and J J van Hilten; Hyperacusis in patients with complex regional pain syndrome related dystonia. J Neurol Neurosurg Psychiatry. 2007 December; 78(12): 1310–1313.