Reflex sympathetic dystrophy (RSD), also known as complex regional pain syndrome (CRPS), is a chronic, painful, and progressive neurological condition that affects skin, muscles, joints, and bones. The syndrome usually develops in an injured limb, such as a broken leg, or following surgery. However, many cases of RSD involve only a minor injury, such as a sprain. And in some cases, no precipitating event can be identified.

Pain may begin in one area or limb and then spread to other limbs. RSD/CRPS is characterized by various degrees of burning pain, excessive sweating, swelling, and sensitivity to touch. Symptoms of RSD/CRPS may recede for years and then reappear with a new injury.

Types
Two types of RSD/CRPS have been defined:

• Type 1 - without nerve injury

• Type 2 (formerly called causalgia) - with nerve injury

Both types share the same signs and symptoms.

Causes
RSD/CRPS appears to involve the complex interaction of the sensory, motor, and autonomic nervous systems, and the immune system. It is thought that brain and spinal cord (central nervous system) control over these various processes is somehow changed as a result of an injury.

Causes associated with the onset of RSD/CRPS include the following:

• Trauma (e.g., bone fracture, gunshot and shrapnel wounds)
• Surgery
• Cerebral lesions
• Heart disease, heart attack
• Infection
• Paralysis on one side of the body (hemiplegia)
• Radiation therapy
• Repetitive motion disorder (e.g., carpal tunnel syndrome)
• Spinal cord disorders

In 10% to 20% of cases, no direct cause can be found. Injury that precedes the onset of RSD/CRPS may or may not be significant.

Signs and Symptoms
The symptoms of RSD/CRPS may progress in three stages—acute, dystrophic, and atrophic.

Seeking Medical Advice
Any patient who is experiencing continued pain after an injury, especially associated with buring discomfort, redness, warmth, hypersensitivity to light touch, swelling, shiny skin or nail growth changes should seek the evaluation of a pain management specialist.

In addition, any patient who is experiencing an unexplained worsening of pain from an injury that should have been improving over time should do the same.

If pain is spreading to the other non affected extremity (either the lower or even the non affected upper extremity) it should prompt the patient to seek medical evaluation from a specialist who is familiar with RSD

Screening and Diagnosis
RSD/CRPS can be difficult to diagnose and often requires excluding other conditions that produce similar symptoms. A thorough history and neurological examination are of utmost importance. During the exam, the clinician may notice that the response to mild sensory stimuli produces severe pain.

Physical examination involves observing the skin color and temperature, swelling, and vascular reactivity; overgrown and grooved nails; swollen and stiff joints; muscle weakness and atrophy.

Other conditions are ruled out with appropriate testing that may include MRI scan, a full laboratory panel, electrophysiological studies of the nerves and muscles (e.g., EMG, NCV), and a test known as a thermogram, which uses an infrared video camera to measure the emission of heat from the affected limb. EMG and NCV tests can be used in combination and are often referred to as EMG/NCV studies.

Treatment
The goals of treatment are to control pain and to maintain as much mobilization of the affected limb as possible. An individualized treatment plan is designed, which often combines physical therapy, medications, nerve blocks, and psychosocial support.

Medication
Medications are prescribed to control pain. The type of pain experienced by the patient determines the type of medication prescribed.

Constant pain caused by inflammation is treated with nonsteroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, naproxen, indomethacin). Due to potenially severe gastrointestinal and cardiovascular side effects, NSAIDs should only be used as instructed.

Constant pain not caused by inflammation is treated with central acting agents such as tramadol (Ultram®).

Sharp pain and pain that disrupts sleep may be treated with antidepressants (e.g., amitriptyline, doxepin, nortriptyline, trazodone) or anticonvulsants (e.g., carbamazapine, gabapentin). Oral lidocaine, a somewhat experimental treatment for RSD/CRPS, also may be prescribed.

Generalized, severe pain that does not respond to other medications may be treated with opioids (e.g., propoxyphine, codeine, morphine).

Muscle cramps (spasms and dystonia) can be treated with clonazepam and baclofen.

Localized pain related to nerve injury may be treated with Capsaicin® cream, but its effectiveness has not been proven.

Medications that affect the sympathetic nervous system such as clonidine (Catapres®) can be useful in some cases.

Muscle stiffness may be treated with muscle relaxants such as

• Tizanidine (Zanaflex®)

• Baclofen

• Clonazepam (Klonopin®)

Physical Therapy
Physical therapy should include daily range of motion exercises. Patients should be advised to avoid activities that could accelerate osteoporosis or joint injury.

Nerve Block
Sympathetic nerve block interrupts the transmission of pain signals from a group of nerve cell bodies (called a ganglion). When treating an upper extremity, it is called a stellate ganglion block. A small needle is used to inject a local anesthetic alongside the windpipe. When treating a lower extremity the nerve block is performed in the lower (lumbar) spine, and is termed “lumbar sympathetic block”.

The procedure, which is usually performed by an anesthesiologist familiar with the technique, involves the insertion of a needle into the appropriate location and the injection of anesthesia into the ganglion. The effect is monitored over time.

Sympathectomy
Patients who have a good but temporary response to nerve block may be candidates for a surgical procedure called sympathectomy. The goal of this procedure, which involves cutting and sealing (cauterizing) a portion of the sympathetic nerve chain that runs down the spine, is suppression of sympathetic nervous system activity in the affected area. Performing sympathectomy for RSD is controversial and in some cases, the procedure worsens symptoms.

TENS Unit
A transcutaneous electrical nerve stimulation (TENS) unit may be used to treat the affected area. In some cases, spinal cord stimulators are implanted permanently to supply a low intensity impulse to a location in the spinal cord in an attempt to interrupt the pain signals that are being transmitted to the brain.

Psychosocial Support
RSD/CRPS patients often become depressed and anxious because of chronic pain and loss of physical ability. Counseling, support groups, and chronic pain center programs help patients learn coping strategies and provide emotional and psychological support.

Prevention
Prevention of RSD/CRPS from progressing centers around the early diagnosis and aggressive treatment with physical therapy and nerve blocks to facilitate such mobilization. Adjuvant medications also may play an important role in successful early cure or remission.

Physicians who are treating patients at risk for these conditions need to keep a vigilant eye on any patient who is not responding to treatment, or who is showing early or even late signs of sympathetic dystrophy. Any patient who appears to be malingering, or requesting continued amounts of analgesics should be assessed for a possibly RSD, and should not just be labeled as narcotics seeking, or malingering.