Complex regional pain syndrome

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1 Date:28/5/14 Time:22:47:21 Page Number: 46 Section 1 Chapter 7 Neurological Disorders Complex regional pain syndrome Gaurav Jain and Nashaat N. Rizk Case study A 50-year-old woman sustained an injury to her right wrist after a computer fell on it. A few weeks later she had pain and swelling in her right wrist. All wrist movements were painful. Due to the possibility of tendon injury, a plastic surgeon operated on her wrist and found no abnormalities. After surgery, her pain worsened. She was unable to use her right hand due to pain and weakness. Gradually, she started to notice that the right hand felt colder and looked paler than the other hand. She had poor nail growth and the skin on her affected hand became dry. 1. What are the differential diagnoses in this case? Cellulitis Lymphedema Soft tissue or bone injury, including occult or stress fracture Compartment syndrome Arthritis or arthrosis Tenosynovitis Upper or lower limb venous thrombosis Arterial insufficiency such as thromboangiitis obliterans or severe atherosclerosis Scleroderma Plexitis, peripheral neuropathy Erythromelalgia 2. What is complex regional pain syndrome? Complex regional pain syndrome is a chronic regional (not in a specific nerve territory or dermatome) pain syndrome that occurs most often in an extremity in association with abnormal autonomic nervous system activity and trophic changes. The pain is seemingly disproportionate in time or degree to the usual course of any known trauma or other lesion. The disorder has both nociceptive and neuropathic features and is characterized by disabling persistent pain, hyperalgesia or allodynia, swelling, vasomotor instability, sudomotor abnormality, and impairment of motor function. In many cases, the syndrome is preceded by an inciting noxious event, surgery, trauma, or immobilization, while in some cases there is no precipitating trauma at all (9%). However, the condition is not related to trauma severity. The syndrome shows variable progression over time. Transient features of CRPS are much more common than most clinicians realize, occurring in up to 25% of minor limb injuries. Approximately 15% of sufferers will have unrelenting pain and physical impairment up to 5 years after CRPS onset, although more patients will have a lesser degree of ongoing pain and dysfunction impacting their ability to work and function normally. The incidence per person-years at risk of CRPS based on the results of two epidemiologic studies ranged from 5.46 to 26.6/ person-years at risk. It is commoner in females than males, at a ratio of 2 3:1, and frequently occurs in the 5th 7th decade of life. 3. What are the classification and diagnostic criteria of CRPS? CRPS is classified into two types based on the absence (type I) or presence (type II) of a definable nerve injury. In 1998, the International Association for the Study of Pain (IASP) established the following four criteria that must be present for a clinical diagnosis of CRPS to be made: 46 Case Studies in Pain Management, ed. Alan David Kaye and Rinoo V. Shah. Published by Cambridge University Press. Cambridge University Press 2014.

2 Date:28/5/14 Time:22:47:22 Page Number: 47 Table 7.1. CRPS categories, symptoms, and signs Category Symptom Sign (evidence needed on exam) Sensory Hyperesthesia and/or allodynia Hyperalgesia (to pinprick) and/or allodynia (to light touch and/or temperature sensation and/or deep somatic pressure and/or joint movement) Vasomotor Sudomotor/ edema Motor/ trophic Temperature asymmetry and/or skin color changes and/or skin color asymmetry Edema and/or sweating changes and/or sweating asymmetry Decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin) Temperature asymmetry (< 1 C) and/or skin color changes and/or asymmetry Edema and/or sweating changes and/or sweating asymmetry Decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin) 1. Preceding noxious event without (CRPS I) or with obvious nerve lesion (CRPS II). 2. Spontaneous pain or hyperalgesia-hyperesthesia not limited to a single nerve territory and disproportionate to the inciting event. 3. Edema, skin blood flow (temperature), or sudomotor abnormalities, motor symptoms, or trophic changes present in the affected limb, in particular at distal sites. 4. Other diagnoses are excluded. Although the IASP diagnostic criteria had a high sensitivity, their specificity was only around 40%. In 2007, the Budapest Consensus refined the diagnostic criteria to include stricter conditions for clinical diagnosis, which increased the specificity to about 70% while maintaining high sensitivity. The criteria were as follows: 1. Continuing pain disproportionate to any inciting event 2. Must report at least one symptom in three of the four below categories 3. Must display at least one sign at time of evaluation in two or more of the below categories 4. No other diagnosis better explains the signs and symptoms (see Table 1) Schwartzman et al divided CRPS into three clinical stages, which are useful descriptively. The syndrome may not always follow this stepwise evolution. The stages of CRPS are described as follows: i. Stage 1: severe pain; pitting edema; redness; warmth; increased hair and nail growth; hyperhidrosis may begin; osteoporosis may begin. ii. Stage 2: continued pain; brawny edema; periarticular thickening; cyanosis or pallor; livedo reticularis; coolness; hyperhidrosis; increased osteoporosis; ridged nails. iii. Stage 3: pallor; dry, cool skin; atrophic soft tissue (dystrophy); contracture; extensive osteoporosis. 4. How does one make the diagnosis of CRPS? The pathophysiology of CRPS is poorly understood. Based on current literature, several hypothesized mechanisms appear to play roles: autonomic dysfunction, neurogenic inflammation, and neuroplastic changes within the central nervous system (central/peripheral sensitization and progressive small-fiber degeneration). Currently no diagnostic test is considered a gold standard and no objective test is specific for CRPS. CRPS is primarily a clinical diagnosis. However, several diagnostic studies may be helpful in its evaluation and to rule out other pathologic processes. Autonomic function can be assessed by following tests: infrared thermometry and thermography, quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test (TST), and laser Doppler flowmetry. For example, skin temperature can be measured by Doppler flowmeter and infrared thermography; cutaneous blood flow can be measured by vital capillaroscopy (the affected extremity may demonstrate higher perfusion); sweat output can be assessed by quantitative sudomotor axon reflex testing; and coexisting nerve injury and muscle fiber loss can be quantified by electromyography and nerve conduction studies. The limitations of these tests are that most require special 47

3 Date:28/5/14 Time:22:47:22 Page Number: 48 equipment and setup that make clinical applications less viable. Imaging has historically been used to exclude other diagnoses. Plain films are usually normal except in extreme cases, in which demineralization can occur (Sudeck s atrophy). Trophic changes can be assessed by threephase bone scintigraphy, which detects pathologic delayed uptake in the distal bones such as the metacarpophalangeal or metacarpal bones. The sensitivity and specificity of three-phase bone scintigraphy are variable. Although an abnormal bone scan finding can confirm the clinical diagnosis of CRPS, the condition cannot be ruled out by a normal study. Magnetic resonance imaging may demonstrate marrow edema, soft tissue swelling, and joint effusion. Although clinically unavailable, central nervous system functional imaging studies may provide clues to reorganization in central somatosensory and motor networks, which lead to an altered central processing of tactile and nociceptive stimuli, as well as to an altered cerebral organization of movement. 5. What is the treatment approach for CRPS? Prompt diagnosis and early treatment is required to avoid secondary physical problems associated with disuse of the affected limb and the psychologic consequences of living with undiagnosed chronic pain. Early referral to physiotherapy and encouraging gentle movement as early as possible may potentially prevent progression of symptoms. Except in mild cases, patients with CRPS are generally best managed in specialist pain management or rehabilitation programs. An integrated and interdisciplinary pain rehabilitation treatment approach that includes the following four components is required: a. Patient information and education b. Pain relief with medications and procedures c. Physical and vocational rehabilitation d. Psychologic interventions (pain-coping skills, biofeedback, relaxation training, and cognitive behavior therapy) Treatment with medications and procedures can be individualized according to the symptoms, signs, and degree of severity. Tricyclic antidepressants are traditional choices in neuropathic pain disorders with good evidence to support their use for neuropathic pain. Antiepileptic agents are some of the best-studied agents for neuropathic pain, and strong evidence demonstrates their effectiveness. Non-steroidal antiinflammatory drugs may be effective in the acute phase with symptoms of swelling, erythema, or warmth. Oral corticosteroid agents can be particularly effective early in the disease when significant inflammation is present, and their use is substantially supported by randomized controlled clinical trials. A short course of steroids in the acute stage of the disease may be indicated. The lidocaine patch is used Figure 7.1. Lumbar sympathetic block. From personal files of Rinoo V. Shah, MD, MBA. 48

4 Comp. by: KNarayanan Stage: Proof Chapter No.: 7 Date:28/5/14 Time:22:47:22 Page Number: 49 Title Name: KayeandShah Figure 7.2. Stellate ganglion block. From personal files of Rinoo V. Shah, MD, MBA). Figure 7.3. Spinal cord stimulation. From personal files of Rinoo V. Shah, MD, MBA). Figure 7.4. Cervical spinal cord stimulation midline/dorsal columns. From personal files of Rinoo V. Shah, MD, MBA. topically to deliver medication locally to the area of allodynia. Because of the suspected role of increased sympathetic nervous system activity in CRPS, alphaadrenergic antagonists such as phenoxybenzamine and phentolamine have also been used and may be beneficial in cases of sympathetically maintained pain. Opioids may be useful in the acute stages of CRPS for pain control. However, their use in chronic pain conditions and conditions with neuropathic features remains controversial. Methadone may be a choice in cases of severe neuropathic pain because of its NMDA receptor antagonist activity. Bisphosphonates have been tested in randomized controlled trials with some demonstrated efficacy, with the assumption that antinociceptive effect is primarily due to their capacity to inactivate osteoclasts and inhibit prostaglandin E2, proteolytic enzymes, and lactic acid. Calcitonin is another recent addition to the CRPS drug therapy armamentarium. However, results of randomized trials have been equivocal. 49

5 Date:28/5/14 Time:22:47:23 Page Number: What interventional methods are available to treat CRPS? Local anesthetic sympathetic blockade is the conventional and most common early intervention. However, patients can be divided by those with sympathetically maintained pain and those with sympathetically independent pain based on positive or negative response to selective sympathetic blockade or blockade of the alpha-adrenergic receptors. Stellate ganglion blocks for upper limb and lumbar chain blocks for lower limb symptoms can be offered. Alternatively, intrapleural infusion of local anesthetic can be used to block the sympathetic chain from T1 to L2. Bier block procedures, involving the intravenous infusion of pharmacologic substances into a limb after gravitational drainage of the venous bed, may also be used. Depending on the substance infused, this can accomplish regional sympathetic blockade with guanethidine, sensorimotor blockade with lidocaine, or a combination of the two. For those patients with sympathetically independent pain, regional sensorimotor blockade with lidocaine should be the early intervention of choice. Such procedures have the possibility of achieving rapid and effective pain relief, allowing more timely progression in rehabilitation. In addition to interventional pain control procedures, which should be used aggressively early in the disease course, spinal cord stimulation (SCS) can be a beneficial treatment modality for those who do not have a satisfactory response to the above treatment in weeks. SCS has been shown to be effective for treatment of both CRPS I and CRPS II when other less invasive treatment strategies have failed. Neuromodulation may act to restore normal gamma-aminobutyric acid levels in the dorsal horn and affect release of adenosine, thus reducing neuropathic pain. SCS has proven effective in supporting functional restoration in the affected limb. Peripheral nerve stimulation uses a similar technique to SCS. However, due to a new modality, available data is limited. A spinal cord stimulator lead can sometimes be placed in the dorsolateral Figure 7.5. Same patient as Figure 7.4: cervical spinal cord stimulation midline (dorsal columns) and dorsal root/entry zone stimulation. From personal files of Rinoo V. Shah, MD, MBA.) epidural space to target the dorsal roots or dorsal root entry zone. Patients who have a good response to sympathetic blocks can be offered sympathetic denervation through radiofrequency ablation or surgical sympathectomy. However, the quality of evidence for these treatments is poor and several complications can occur, which include postsympathectomy sympathalgia, compensatory hyperhidrosis, Horner s syndrome, infection, and spinal cord injury. Sometimes CRPS may spread to the contralateral limb or to involve a different region of the body. Surgeons operating on patients with resolved or dormant CRPS must be aware of reactivation and spread of this disease, even if the surgery is remote to the original CRPS involved limb. If recurrence and spread occur, blocks and infusions targeting the sympathetically independent and maintained pain generators should be pursued, according to Shah and Day. [15] 50 References 1. Janig W, Stanton-Hicks M (eds). Reflex sympathetic dystrophy: a reappraisal. In Progress In Pain Research and Management, vol. 6. Seattle, Washington: IASP Press; Harden RN, Bruehl S, Stanton- Hicks M et al. Proposed new diagnostic criteria for complex regional pain syndrome. Pain Med. 2007;8: de Mos M, de Bruijn AGJ, Huygen FJPM, et al. The incidence of complex regional pain syndrome:

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