Researchers find mirror fools phantom limb pain

BOSTON (Reuters) - Viewing the reflected image of an intact limb in a mirror can fool the mind into thinking that a lost leg or foot still exists, dramatically relieving phantom limb pain, researchers reported on Wednesday.

At least 9 out of 10 amputees report feeling sometimes-severe pain in the missing limb, often the result of a sensation that the arm or leg is stuck in the wrong position. The sensation can be excruciating and pain drugs often do little to help.

But some studies have suggested that using a mirror to trick the mind into thinking the lost limb is still there may help. Doctors do not understand why it works, but it appears to help a confused brain reconcile sensations coming from the severed nerves.

Dr. Jack Tsao, a Navy neurologist at the Walter Reed Army Medical Center in Washington, asked 22 volunteers, most of whom had lost part of a leg in Iraq, to try one of three therapies.

With the mirror technique, patients saw a reflected image of their intact limb as they spent 15 minutes a day trying to move legs and feet. The setup gave the illusion that the missing limb was present and moving normally.

Another group looked at a mirror covered by an opaque sheet as they tried to perform the same task. A third group was asked to close their eyes and spend 15 minutes imagining their limb moving normally.

During the first four weeks of treatment, pain intensity dropped dramatically in the mirror group, going from an average score of 30 to about 7 on scale up to 100. Every person in that group reported less pain.

For those looking at the covered mirror, their average pain score increased to about 60, in part because only one volunteer said he felt less pain while three said their pain became worse.

Among people who imagined their limb moving, the pain score increased to about 60 after the first week, but then rapidly diminished.

Then, during the next four weeks, all the patients were switched to the mirror technique. Their pain scores diminished significantly in eight out of nine cases.

"The majority of people got some relief. The range went from some relief to completely gone," Tsao said in a telephone interview. "We were surprised that the effect was so strongly positive.""

The team is planning a similar test in people who have lost arms.

The idea of mirror therapy has been around for at least a decade, but it has not been widely adopted because "there's never been a controlled study done before," Tsao said.

The technique may relieve pain by helping the brain reconcile what the body is feeling with what the eyes are seeing, Tsao said.

"Although the underlying mechanism accounting for the success of this therapy remains to be elucidated, these results suggest that mirror therapy may be helpful in alleviating phantom pain in an amputated lower limb," his team wrote in a letter to the New England Journal of Medicine.

"It's certainly my hope that more rehab centers will try this," Tsao said.

(Reporting by Gene Emery; Editing by Maggie Fox and Jackie Frank)