Miscellaneous Pain Disorders that Affect Multiple Areas of the Body
Complex Regional Pain Syndrome (Formerly Known as Reflex Sympathetic Dystrophy or Causalgia)
Complex regional pain syndrome (CRPS) is defined as a syndrome of diffuse limb pain, often burning in nature, usually a consequence of injury or painful stimulus. CRPS was first described in 1864 during the Civil War. Most soldiers went through a normal recovery period from superficial gunshot wounds, but for some a chronic pain syndrome developed. The pain was characterized by a severe burning sensation. These soldiers would go on to have painful limbs with marked dysfunction. The distribution of pain was inconsistent, not representing a single dermatome or peripheral nerve, distinguishing it from a single-nerve injury. Skin, hair, and nail changes developed in affected limbs.1
CRPS can occur after a major event such as knee surgery or after a minor event such as bumping your shoulder. Some common precursors include trauma, surgery, inflammation, nerve injury, stroke, and immobilization. CRPS is divided into two types: Types I and II. CRPS Type I, formerly known as reflex sympathetic dystrophy, occurs when there is no known preceding nerve damage—for example, an ankle sprain. No correlation exists between the severity of the injury and the resulting painful syndrome.1 In 5% to 10% of patients, there is an absence of any painful event. Type I is more common than Type II. CPRS Type II, formerly known as causalgia (literally “hot pain”), occurs when there is apparent preceding nerve damage. The incidence after known peripheral nerve injury ranges from 1% to 14% in different series.
CRPS frequently occurs in young adults and is more common in females than males. No specific psychological factor or personality trait has been identified that predisposes individuals to the development of CRPS.
There is no definitive agreement among clinicians regarding the pathophysiology of CRPS. One of the main theories postulates that after a painful stimulus the body normally sends out a sympathetic discharge. If that discharge were to continue aberrantly without shutting down, this could lead to a sympathetic hyperdynamic state.2 A continued sympathetic hyperdynamic state would cause peripheral tissue damage, generating further sympathetic discharge and perpetuating the vicious cycle (Fig. 7-1).
Eventually this leads to both peripheral and central nervous system (CNS) changes that exist independent of the sympathetic state. In recent years, the concept of a sympathetic cause has been challenged because a subset of patients with presumed CRPS do not respond at all to sympathetic block. This led to the name change from reflex sympathetic dystrophy to CRPS.
Eventually this leads to both peripheral and central nervous system (CNS) changes that exist independent of the sympathetic state. In recent years, the concept of a sympathetic cause has been challenged because a subset of patients with presumed CRPS do not respond at all to sympathetic block. This led to the name change from reflex sympathetic dystrophy to CRPS.
 Figure 7-1 Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy. Suspected vicious pain cycle. |
History and Examination
On history, CRPS sufferers often describe a constant burning pain in a limb, sometimes also described as an aching pain. Symptoms usually progress in a stepwise fashion, though not in every instance, with pain and decreased function always present. Hallmarks of CRPS are hyperalgesia (an exaggerated response to painful stimuli) and when the disease advances, allodynia (the sensation of pain to nonpainful stimuli, e.g., merely touching the skin). Initially there may be signs of increased sympathetic tone, such as increased sweating in the limb and temperature changes.3 Vasomotor changes cause skin discoloration, including various hues of red and purple. Sudomotor changes in skin range from hyperhidrosis to bone-dry skin. It is important to note that vasomotor and sudomotor changes vary not only among individuals but also within individuals over time.4 Later there may be physical trophic changes such as glossy skin, brittle nail growth, altered hair growth, and muscle atrophy. These changes usually develop months after the pain begins (Fig. 7-2).
CRPS may remain stable affecting the same area or may spread in three distinct patterns: Contiguous, independent, and mirror image. In contiguous spread, there is gradual enlargement of the area affected—from distal to proximal of the affected limb. In independent spread, there are signs and symptoms that develop at a site distant from the original symptoms, for example, symptoms spreading from the right leg to the left arm. In mirror image spread, symptoms appear in the opposite limb in a region similar to the site of initial presentation.
 Figure 7-2 Physical changes seen in complex regional pain syndrome. The left hand has color changes and appears glossy. |
The physical examination varies greatly depending on when the patient is seen—in the early stages of CRPS or after the syndrome is full blown. Patients at all stages will tend to protect the painful limb—an arm will be folded in or a painful leg pulled back. Touching the affected limb will be very unpleasant for the patient. As the process becomes chronic, you may see the skin of the painful limb become glossy. There may be atrophy as well. The hair growth and nail beds are different between the painful and nonpainful limb. CRPS should be suspected if regional pain and sensory changes after a trauma exceed the duration or magnitude of the anticipated healing period. The key is not to wait for the chronic changes to develop before recognizing that this may be CRPS and administering treatment. If you have a reason to suspect CRPS, start treatment immediately.
CRPS is a diagnosis of exclusion, but in some cases, changes on a triple-phase bone scan may aid in confirmation. There is an increase in bone metabolism as shown by increased periarticular tracer uptake using a triple-phase bone scan. However, an abnormal bone scan is not required for the diagnosis of CRPS. These changes are not seen until at least 3 months after the symptoms start; treatment should begin before a triple-phase bone scan is performed to maximize the chance of effective treatment.
Treatment
Treatment is based on functional restoration. This often requires a multidisciplinary approach, including sympathetic nerve blocks, possibly a spinal cord stimulator, medication management, physical therapy, and control of any psychological dysfunction that may develop. Many patients with CRPS have anxiety, fear, depression, and other psychological symptoms. This is considered to be a result of and not a cause of CRPS.
Sympathetic Nerve Block
Treatment usually involves interventional sympathetic block of the region affected. The physician injects anesthetic solution under x-ray guidance onto the stellate ganglion (part of the sympathetic chain) for upper-extremity CRPS or the lumbar sympathetic chain for lower-extremity CRPS. Sympathetic nerve blocks can break the pain cycle. For years this was considered the gold standard of treatment. However, there are few well-controlled studies that have been conducted to determine the usefulness of
sympathetic block. When grouped together, these studies show that 29% of patients obtain full pain relief whereas 41% obtain partial pain relief.5 These numbers should be considered with caution as the studies are older & limited. Sympathetic blocks become less effective the more chronic the condition. In a study looking at sympathectomy (permanently cutting the sympathetic chain) the most important independent factor in predicting a positive response to sympathectomy is an interval of less than 12 months between the inciting event and the procedure.6 Sympathetic nerve block is used in conjunction with physical therapy with the goal of allowing the patient to participate fully in the exercises with less pain. See the chapter on sympathetic blocks, Chapter 24, to learn how these procedures are performed.
sympathetic block. When grouped together, these studies show that 29% of patients obtain full pain relief whereas 41% obtain partial pain relief.5 These numbers should be considered with caution as the studies are older & limited. Sympathetic blocks become less effective the more chronic the condition. In a study looking at sympathectomy (permanently cutting the sympathetic chain) the most important independent factor in predicting a positive response to sympathectomy is an interval of less than 12 months between the inciting event and the procedure.6 Sympathetic nerve block is used in conjunction with physical therapy with the goal of allowing the patient to participate fully in the exercises with less pain. See the chapter on sympathetic blocks, Chapter 24, to learn how these procedures are performed.
Spinal Cord Stimulation
This procedure has been used with success for a number of neuropathic pain conditions. The medical device consists of polyurethane leads and a small battery analogous to a pacemaker—it has been called the pacemaker for pain. The flexible catheter style leads placed into the posterior epidural space never physically touch the spinal cord. Current is used to drive controlled electrical stimulation to the back of the spinal cord and stimulate the large myelinated fibers of the dorsal horn, which has been shown to inhibit pain. In a study by Taylor et al.,7 patients with CRPS reported a statistically significant reduction in the visual analog pain scale at 24 months after a spinal cord stimulator implant. Almost two-thirds of patients reported at least a 50% improvement in their pain scores over a median follow-up period of 33 months. In another study looking at functional status of patients with sympathetically maintained CRPS Type I, spinal cord stimulation reduced deep pain and allodynia. Patients showed significant improvement in their motor strength over an average follow-up of about 3 years.8 The advantage of spinal cord stimulation is that the patient gets to experience the device on a trial basis for 3 to 5 days to test its efficacy before deciding to permanently implant the leads and battery.
Medication
There are very few placebo-controlled trials on medication use for CRPS. Antiseizure and antidepressant medications used to treat neuropathic pain are often clinically applied in these cases. If an opioid is used, methadone—with its NMDA receptor antagonist properties—may be the most appropriate choice to treat if the pain is severe in this chronic painful condition.
Physical Therapy
Physical therapy helps facilitate functional recovery of the limb. The direct goals are desensitization of the affected region, mobilization, increasing strength and range of motion, and vocational and functional rehabilitation. The effect of physiotherapy on the natural course of the disease is unknown. However, it is important to remember that nearly all patients with advanced CRPS also have myofascial pain syndrome of the supporting joints because of their contracted state.
Case Study
Case
A 47-year-old female presents with pain in her right lower extremity. The patient was at work and a clothing rack fell, hitting her shin. She was able to work the rest of the day. The next day she noticed a bruise on her shin. Over the last 3 months the pain in her right lower extremity has increased; she describes the pain as burning in nature. The patient has seen another primary care doctor, who prescribed Neurontin (gabapentin), which she states has not been very helpful for her pain at 300 mg qhs.
On examination, you elicit pain in her right leg with a simple touch. The pain is located circumferentially around her calf down to her feet. Previous x-rays were negative and the patient has no past medical history. At this point, you suspect CRPS Type I and send the patient to pain management for a series of lumbar sympathetic blocks. The patient returns to your office 10 months later. You notice that even though it is winter she is wearing sandals and she keeps her right leg pulled back. The patient reports that the pain has increased significantly and her leg has changed. She reveals that she was scared about having an injection and never went to pain management. The right foot clearly is atrophied and the skin looks glossy. The patient states that even her bedsheets touching her leg causes pain. The decision is made to start the patient on Lyrica with an aggressive titration schedule. You call the pain management group and negotiate a next-day appointment. The patient keeps this appointment; she undergoes a series of lumbar sympathetic blocks that helps alleviate the burning pain somewhat but overall provides only moderate relief. At this point it is agreed that the next step is to proceed with a spinal cord stimulator trial. The patient has pain relief with the trial and decides to proceed with full implantation, which is performed 2 weeks later. The patient currently is in physical therapy on Lyrica with the stimulator covering the area of her pain. There is a significant reduction in her pain; however, she has still not been able to return to work.
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