1. Complex Regional Pain Syndrome
Jeremy Bennett

2. CRPS History
CRPS (complex regional pain syndrome) initially considered in early 1800s by Claude Bernard et al.
During the Civil War it was seen that soldiers who suffered from low-velocity, high-mass missile injuries developed a neuropathic pain that was termed "causalgia" by Silas Weir-Mitchell.
In 1940s the term of reflex sympathetic dystrophy came into use relating the belief of an abnormal efferent reflex from the sympathetic nervous system to bodily injury.
Since that time much study and frustration has come from this relatively rare condition of which the pathophysiology is still not fully understood.
CRPS is rare, but has started to see an increase in dx.

3. Basics
Often seen after injury to a limb or related to some inciting event.
The patient complains of and can manifest skin color/ temperature/ appearance changes in the affected limb.
Pain often excruciating – burning, tingling, electric-like, etc. are often symptoms that patients feel. The pain is often out of proportion to stimulus or the event.

4. Physical Appearance

5. Diagnostic Criteria
IASP (International Assoc for the Study of Pain) diagnostic criteria include 4 subjective and/ or objective findings:
1. The presence of an initiating event or a cause of immobilization – peripheral injury or central (stroke, etc)*. (Injury)
2. Continuing pain, allodynia, or hyperalgesia in which the pain is disproportiate to inciting event. (Sensory)
3. Evidence of edema, changes in skin blood flow, or abnormal sudomotor activity in region of pain. (Vasomotor)
4. Diagnosis is excluded by the existence of other conditions that would otherwise account for the degree of pain/ dysfunction.
One symptom from each category (except #1 as 5% of pts lack known event) and at least one sign from 2 categories must be evident to diagnose CRPS, at least by research criteria.
*Not always present or identifiable.

6. CRPS More Widely Diagnosed
Quickly becoming more recognized, and possibly overly diagnosed for several reasons:
The standardization of diagnosis.
The "discovery" by personal injury lawyers who use it as a tool for settlements.
New treatments and research for chronic pain.
Patient self-research and the internet.

7. Diagnostic Si/Sx
The most common pain finding is a "burning" and "stinging” sensations that occur spontaneously. This is seen in as many as 87% of cases. 
69% of patients report hyperesthesia with light touch (such as clothing laying on the skin or even draughts of blowing wind).
Vasomotor dysfunction is manifested by asymmetrical edema in affected limb, skin color and temperature changes, abnormal sweating (either hyperhidrosis or anhidrosis), and skin/ nail changes.
Patients may also complain of muscle jerking, myoclonus, or rigidity in affected limb including contractures of hands and feet.

8. CRPS II
The majority of patients seen are diagnosed with CRPS type I – or reflex sympathetic dystrophy (RSD). This is the less painful, debilitating of the two.
CRPS II (causalgia) is related to a known injury to a specific major nerve with neuropathic pain frequently following along the distribution of that nerve alone, though not always.
While the diagnostic criteria of the IASP may apply, these patients may also demonstrate hypoesthesia in the nerve distribution associated with electrical shocks and extreme allodynia. This is rarer than CRPS I and the patients are often more debilitated.

9. Treatment Treatment usually consists of several objectives:
Functional restoration of affected limb - often should be considered first before other treatments
Sympathetic and/or motor blocks
Cognitive behavioral techniques
Psychotherapy
Pharmacotherapy
Occupational and physical therapy

10. Tx – Functional Restoration
Functional restoration involves steady progression from gentle movements to gentle, weight bearing movement. Results in more active load bearing with expected gradual desensitization and increased functionality of limb.
Examples include moving from silk stimulation to other cloths and textures, the scrub and carry technique, and contrast baths that widen the temperature range that the patient can tolerate.
If limitations occur then addition of blocks, pharmacotherapy, etc. can help increase the patient's tolerance and improvement.

11. Tx - Psychotherapy
Psychotherapy is critical to improvement in patients with CRPS. There is a high incidence of depression and anxiety noted in many CRPS patients. Unknown at this time if antecedent psychological factors prior to injury are common. 
CRPS patients also develop a type of PTSD termed "kinesophobia" or fear of movement related to prior pain or initial injury. The patient develops "negative reinforcements" through fear of initial movements that caused the injury of prior movements that resulted in extreme pain in the past. Fear of movement often results in contractures and reduced functionality.
Cognitive behavioral therapy is the most beneficial psychotherapy to help patients with these concerns, though other interventions including family therapy are also beneficial.

12. Tx - Pharmacotherapy
Pharmacotherapy is often on a trial and error basis and is very patient specific. Drugs are considered based on neuropathic pain treatments and then used for CRPS and have yet to be shown effective in RCTs.
 - initial drug(s) to consider include gabapentin and pregabalin (both used for neuropathic pain) and are approved for these conditions
- TCAs often used for patients with sleep disturbances, but are hindered by their numerous side effects and drug interactions; not currently approved for pain treatment

13. Tx - Pharmacotherapy
- SSRIs and SNRIs like fluoxetine and duloxetine, resp, are often used with the latter being approved for neuropathic pain conditions.
- Opioids should be avoided as much as possible as their effectiveness is not well proved and dependence/ addiction are serious concerns in CRPS patients.
- Intrathecal baclofen, IV steroids, IVIG, and anticonvulsant medications are all treatments that have been considered and used with variable success, though studies are still lacking.

14. Tx – Interventional Approaches
Considering the nature of the sympathetic involvement in the patient, blocking the sympathetic nervous system seems inherent towards improvement.
Cervical and lumbar sympathetic blocks are frequently performed as outpatient procedures with patients receiving a few weeks or months of relief. Often done to help with movement therapies.
Beir blocks with local anesthetics, guanethidine, or other neurolytic agents have been performed with varying success.
SCS, pump implantation, and thermocoagulation have also been used to treat patients with CRPS with variable success rates.

15. Despite the belief that blocking the sympathetic nervous system will result in reduced pain, many patients do not gain substantial benefit from these procedures for any substantial length of time and the procedures themselves may actually exacerbate the patient's pain.

16. CRPS Prognosis
Overall the prognosis for patients with CRPS is relatively low. Effective treatments are very patient specific and patient satisfaction, mental state, willingness to be involved in their treatment all contribute to their pain reduction.
Many patients report extreme lack of satisfaction with their pain control and are usually disabled.
More research is required into chronic pain and developing better methods to treat chronic autonomic dysfunctional pain.

17. References
Harden RN, Complex Regional Pain Syndrome, British Journal of Anesthesia, 2001, 87, pp
Schott GD, Complex? Regional? Pain? Syndrome? Practical Neurology. 2007, 7, pp
Forouzanfar T, et al. Treatment of Complex Regional Pain Syndrome Type I. European Journal of Pain. Vol 6, issue 2. Apr pp