Still in pain long after a hand or foot injury has healed? It may be that your brain has been re-wired.

Using MRI scans, researchers from Northwestern University have found that people who have a chronic condition called complex region pain syndrome (CRPS) seem to experience changes in the parts of the brain related to emotion, pain perception and skin temperature.

The alterations occur in the network of miniscule white cables, known as white matter, that carry messages between the brain's neurons.

The research gives some credence to a condition that some in the medical community don't believe to be real, said the study's lead investigator A. Vania Apkarian.

Apkarian also said this is the first time that brain abnormalities have been identified in CRPS patients.

"People didn't believe these patients. This is the first proof that there is a biological underpinning for the condition," Apkarian, a physiology professor at Northwestern's Feinberg School of Medicine, said in a statement. "Scientists have been trying to understand this baffling condition for a long time."

The findings are published in the November 26 edition of the journal Neuron.

CRPS affects about five per cent of patients who have suffered hand or foot injuries that have caused considerable damage.

Their pain continues well after the wound has healed and can radiate beyond the hand or foot to encompass the arm, leg or the entire body.

Skin colour can take on a red or blue hue, and skin temperature can rise before becoming colder as the condition wears on.

Previous research has shown that chronic pain can cause the parts of the brain called grey matter, which house neurons, to atrophy.

Patients in this study also had atrophied grey matter.

However, this is the first link between chronic pain and white matter, which provides another target for researchers who are testing potential drug treatments for CRPS patients.

As well, further research will have to be done to determine if CRPS leads to these white-matter changes or if CRPS patients have pre-existing brain abnormalities.

The findings may also help researchers who are investigating the origins of other chronic pain conditions that may involve the reorganization of white matter, Apkarian said.