Reflex Sympathetic Dystrophy
What is reflex sympathetic dystrophy?
Reflex Sympathetic Dystrophy (RSD) is also referred to as complex regional pain syndrome (CRPS), and typically occurs in the upper or lower extremities. There are two types of CRPS: CRPS 1, when pain stems from an initial painful event that may or may not be traumatic, and CRPS 2, when pain stems from an identifiable painful event or nerve injury. Both CRPS 1 and CRPS 2 cause continuous, intense pain out of proportion to the severity of the injury.
What causes reflex sympathetic dystrophy?
The cause of reflex sympathetic dystrophy is still unclear, however, there are several theories. Some theorize that reflex sympathetic dystrophy is maintained by the sympathetic nervous system. Another theory is that CRPS is caused by an immune response that leads to the inflammatory symptoms of redness, warmth, and swelling in the affected area.
There are no specific tests to diagnose CRPS, but testing can be done to rule out other diagnoses that may explain the symptoms. Blood testing can be done to rule out other inflammatory or rheumatologic conditions. Nerve conduction studies can be done to rule out peripheral neuropathy or nerve entrapment conditions. Magnetic resonance imaging (MRI) can be done to rule out any soft tissue causes for the patient’s neuropathic symptoms. The diagnosis of CRPS is made in the absence of these other possible causes for the patient’s pain.
Some common symptoms include drastic changes in the temperature and color of the skin over the affected limb or body part accompanied by severe burning pain, skin sensitivity, sweating, and swelling. Some other key features of CRPS include hyperalgesia (increased sensitivity to painful stimuli) and allodynia (a painful response to a typically non-painful stimulus).
Some nerve blocks for upper extremity pain include stellate ganglion blocks, cervical epidural steroid injections, and interscalene blocks, followed by desensitization.
Injections for lower extremity CRPS include lumbar sympathetic nerve blocks, lumbar epidural steroid injections, and femoral sciatic nerve blocks, followed by desensitization.
Spinal cord stimulation
If the patient does not respond to more conservative treatments, neuromodulation through spinal cord stimulation may be considered. Spinal cord stimulation involves placing small electrodes within the epidural space of the spine.
The theory behind spinal cord stimulation is that stimulation of the large nerve fibers will inhibit the small nerve fibers, thus blocking the sensation of pain. Peripheral nerve stimulation is very similar to spinal cord stimulation, but the electrodes are placed along the peripheral nerves, typically close to the area of pain. Spinal cord stimulation has been a very efficacious treatment modality for over 30 years.
Some medications used for CRPS include gabapentin, pregabalin (Lyrica), duloxetine (Cymbalta), and amitriptyline.