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09.06 >> PAIN    
Why Does the Pain Remain?  
 

Normally, when you scrape your knee or elbow or burn your hand, it heals and the pain ends. For some people, though, the wound goes away, but the pain remains. Along with the pain, the wounded area may swell and sweat, and the skin color and temperature may change. All of these symptoms are often way out of proportion to the original injury.

These are the symptoms of a medical condition called complex regional pain syndrome-1 (CRPS-1). CRPS-1 is hard to treat because doctors do not know the cause.

And, sadly, sometimes the patients have been treated as if the CRPS-1 pain was in their head (psychological) rather than in their body (physiological). They may become depressed and occasionally suicidal. The pain is described as excruciating, but until now its physiological basis was not revealed by any standard test. By designing and confirming a diagnostic procedure, and by explaining the biological basis for the pain, Dr. Oaklander's team has laid the groundwork for possible treatments for patients and has given an important psychological boost to patients: they can now confirm their experience with a simple biopsy.

As a step to learning more, Dr. Anne Louise Oaklander and a team of researchers at Massachusetts General Hospital's Nerve Injury Unit in Boston conducted a study of adults with and without CRPS-1.

Dr. Oaklander and her colleagues studied the skin from 18 adults with CRPS-1. To serve as a control, they also studied 7 adults who did not have CRPS-1, but did have other painful conditions such as osteoarthritis of the knee.

Injured foot

 
The skin from each person was studied in two ways. The first was to test the skin for sensory function. Sensory function tests measured the person's perception of pain when areas of the skin were touched, pressed, and stimulated with heat and cold using special machines made for this type of evaluation. In people with CRPS-1, the sensory function tests found that a light touch or slight heat was felt as extremely painful in the affected areas compared to other parts of their body. The wound that had healed somehow left behind an area of increased painful sensitivity, which was so sensitive that clothing touching the skin produced unbearable pain. The control group, the people with painful conditions but not CRPS-1, did not show any change in sensory perception.

In the second evaluation, each patient was studied by taking skin samples with a skin punch, which removes about 3 mm (about a tenth of an inch) of tissue; this process is called a biopsy. Each person had three skin biopsies under anesthesia. One biopsy was from the area of the most pain, a second biopsy was from a nearby pain-free spot, and the third biopsy was the mirror image site on the opposite side of the body. For example, if the right knee was most painful, a biopsy would be taken from the right knee, the right thigh and the left knee. The right thigh and the left knee were the pain-free areas. The skin samples were prepared and stained so the nerve cells could be examined under a high power microscope. The researchers found that the areas identified as painful in people with CRPS-1 had fewer small-fiber nerve cells compared to other parts of their body. Fewer nerve cells make the skin super-sensitive, which produces the painful feelings reported by these people. In contrast, the control group did not have any nerve damage, indicating the pain of osteoarthritis arises from undamaged nerve cells.

From the results, Dr. Oaklander and colleagues concluded that CRPS-1 is a condition in which the nerves on the skin have been damaged. For now, the first treatments are drugs to relieve the pain because there is currently no cure for CRPS-1. If drugs are not effective, surgical options are to block nerve conduction, called an anesthetic block, or implant electrodes under the skin to electrically stimulate the injured nerves. This latter treatment may rewire damaged nerves back to a more normal pathway of sensation. Researchers are hopeful that continued studies will lead to a cure in the future.

Equally important for people with CRPS-1 pain, there is now scientific evidence that their suffering originates in damaged tissue in their bodies and not psychologically. That, too, is important to the well being of patients.

Dr. Anne Louise Oaklander is a neuroscientist and neurologist who has spent most of her career studying pain and what causes it. She is the Founder and Director of the Nerve Injury Unit at Massachusetts General Hospital, Boston, MA. She travels around the world teaching physicians and patients about pain-related diseases and their treatment. In Boston, she teaches at Harvard Medical School and conducts research on the causes of nerve pain in her laboratory.

To Learn More:

About organizations helping those with CRPS:

About CRPS-1:

  • Groopman J., When Pain Remains. The New Yorker, October 10, 2005: pages 36-41.
  • Oaklander AL, Rissmiller JG, Gelman LB, Zheng L, Chang Y, Gott R. Evidence of focal small-fiber axonal degeneration in complex regional pain syndrome-1 (reflex sympathetic dystrophy). Pain 2006; 120:235-243.

About Treatments for CRPS-1:

  • Hord ED, Oaklander AL. Complex regional pain syndrome: a review of evidence-supported treatment options. Current Pain and Headache Reports 2003; 7:188-196.
  • Oaklander, AL. Evidence-based pharmacotherapy for CRPS and related conditions. In: CRPS: Current Diagnosis and Therapy, Progress in Pain Research and Management 2005; 32:1-20.

 

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Dr. Anne Louise Oaklander

Hear an interview about CRPS with Dr. Anne Oaklander.
Interview courtesy of WBZ News Radio 1030 and Jordan Rich. (18mb)


Dr. Anne Louise Oaklander and a team of researchers at Massachusetts General Hospital's Nerve Injury Unit in Boston

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