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Peripheral Nerve Stimulation for Complex Regional Pain Syndrome
Introduction
The taxonomy complex regional pain syndrome (CRPS) was introduced in 1993 by the International Association for the Study of Pain (IASP) to describe the pain syndromes reflex sympathetic dystrophy (type 1) and causalgia (type 2).
CRPS is a conglomeration of symptoms and signs involving autonomic and somatic nerve function, to a debilitating extent, with unknown pathophysiology. The IASP introduced the diagnostic criteria of disproportionate pain, hyperalgesia, allodynia, swelling, discoloration of the skin, and abnormal sudomotor, vasomotor, and motor functions that correlate with the degree of disability and suffering. CRPS is a regional pain syndrome of unclear pathophysiology, typically affecting the hand or foot. CRPS is one of the most challenging chronic pain conditions of the limbs. A diagnosis of CRPS type 1 may include regional pain, sensory changes, edema, and abnormalities of temperature, sudomotor activity, and skin color. CRPS type 2 is differentiated from type 1 by the presence of a definable nerve lesion. The combination of physical and psychological therapy with medical as well as interventional management, followed by spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS), provides an acceptable protocol for treating CRPS type 1, although nonresponders and delayed interventions would demand an earlier interventional procedure to reduce disability with improved outcomes.
Table 33.1 summarizes the difference between CRPS type 1 and CRPS type 2.
Table 33.1
Differences Between Complex Regional Pain Syndrome Type 1 and Type 2
| Type 1 (Reflex Sympathetic Dystrophy) | Type 2 (Causalgia) |
|---|---|
|
|
|
|
|
|
|
|
| Criteria 2–4 must be satisfied | All three criteria must be satisfied |
There is little published information regarding the incidence of CRPS; it is thought to be rare, but is often misdiagnosed. The mean age of patients with CRPS ranges from 36 to 42 years, with a preponderance of women suffering from this clinical entity (60%–81%). The upper extremity is involved in 44% to 61% of cases, and the lower extremity in 39% to 51% of cases. It is well recognized that CRPS can also occur in children.
The most common etiology of CRPS tends to be either sprain/strain or surgical intervention. Table 33.2 elucidates different causes of CRPS.
Table 33.2
Etiology of Complex Regional Pain Syndrome
| Cause | Incidence |
|---|---|
| Fracture | 16% |
| Strain or sprain | 10%–29% |
| Postsurgery | 3%–24% |
| Contusion or crush injury | 8% |
| Spontaneous | 6% |
| Other causes or unknown etiology | 2%–17% |
Clinical Presentation
CRPS type I is characterized by lack of documented injury to the nerve, whereas type II includes cases of identifiable nerve lesion. The hallmark of the disease process is pain, which is out of proportion to the injury, associated with hyperalgesia and allodynia. Associated signs include vasomotor, sudomotor, and trophic changes and passive movement disorders. There are multiple mechanisms of action involved in the underlying pathophysiology of the disease.
Some of the characteristic symptomatology is summarized in Table 33.3 .
Table 33.3
Clinical Features of CRPS
a Galer BS. et al. J Pain Symptom Manage 2000; 20: 286–292
b Birklein F Handwerker HO. Pain 2001; 94: 1–6
c Rommel O. et al. Pain 1999; 80: 95–101
d Thimineur M. et. al Clin J Pain 1998; 14: 256–67
e Birklein F. et al. Pain 1997; 69: 49–54
f Schwartzmann RJ., Kerrigan J. Neurosurgery 1990; 40: 57–61
Management
The goals of treatment are to improve function, relieve pain, and, if possible, achieve remission. Current guidelines recommend an interdisciplinary management emphasizing three core treatment elements:
Pain management: Pharmacotherapy continues to be the early mainstay of the treatment algorithm. A complete overview of pharmacological treatment is beyond the scope of this chapter. Some of the classes of medications that are beneficial in treating CRPS are nonsteroidal antiinflammatory drugs, antidepressants (amitriptyline, desipramine etc.), anticonvulsants (gabapentin, pregabalin, carbamazepine, etc.), opioids, NMDA receptor antagonists (ketamine, etc.), bisphosphonates, N-acetylcysteine, and more.
Functional rehabilitation: This is the key for success in the management of CRPS. Early desensitization therapy and modalities focusing on muscle strength, flexibility, and gait training are part of a comprehensive rehabilitation program.
Behavioral therapy: Uncertainty in cause, course, and treatments can lead to depression and anxiety in patients struggling with CRPS. Cognitive behavioral therapy is the most effective intervention and has shown long-term sustainable outcomes.
If a comprehensive conservative treatment plan continues to be ineffective by 12 to 16 weeks, a trial of aggressive interventional therapies, including neuromodulation treatment options, should be pursued.
Advanced neuromodulation treatment options include SCS, dorsal root ganglion stimulation, PNS, intrathecal baclofen, clonidine, or intrathecal opioid therapy.
PNS has shown to be efficacious in improving function and pain in patients with CRPS. This modality should be considered in carefully selected patients.
Common targets
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