Wednesday, February 22, 2006

Nerve Damage May Underlie Mystery Pain Syndrome

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Nerve Damage May Underlie Mystery Pain Syndrome

NEW YORK (Reuters Health) - The findings from a new study lend support to the hypothesis that the so-called "complex regional pain syndrome" is a bona fide neurologic disorder caused by persistent nerve injury affecting small fibers that can feel pain.

Complex regional pain syndrome involves post-traumatic limb pain and other disturbances that continue even though the inciting injury seems to have healed. The cause of the symptoms is unknown and because there are few objective findings, diagnosis and treatment is difficult. Some have even questioned whether complex regional pain syndrome has a real biologic basis or is a psychosomatic illness.

In the current study, reported in the journal Pain, Dr. Anne Louise Oaklander and colleagues, from Harvard Medical School in Boston, performed sensory testing and quantitative nerve assessment of affected and unaffected sites on 18 patients with complex regional pain syndrome.

Seven subjects without complex regional pain syndrome, but with similar symptoms served as additional controls.

The complex regional pain syndrome patients had classic histories and symptoms for the disorder. Unexpectedly, the researchers found that complex regional pain syndrome onset was often associated with medical procedures.

Sensory testing showed that sites affected by complex regional pain syndrome were highly sensitive to mechanically- and heat-induced pain and also showed decreased nerve fiber densities.

By contrast, control subjects did not display these reductions at their pain sites, "suggesting that pain, disuse, or prior surgeries alone do not explain complex regional pain syndrome-associated neurite losses," the authors state.

"The fact that complex regional pain syndrome now has an identified cause takes it out of the realm of so-called 'psychosomatic illness'," Oaklander said in a statement.

"Our results suggest that complex regional pain syndrome patients should be evaluated by neurologists who specialize in nerve injury and be treated with medications or procedures that have proven effective for other nerve-injury pain syndromes."

SOURCE: Pain, February 2006.

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