Photo/Illutration The Asahi Shimbun

Phantom pain, an agonizing sensory condition that afflicts amputees after the loss of a limb, can now be treated, new research shows.

A team of specialists primarily attached to Osaka University developed a way to ease the pain frequently described as a stabbing, throbbing or burning sensation that those who have lost an arm or a leg experience, often on a continual basis.

The findings, which are expected to lead to the development of new treatment, were published in the U.S. journal Neurology on July 17.

"Until now, there were no therapeutic methods to control data processing in the brain, so many patients simply had to put up with the constant pain," said Takufumi Yanagisawa, a neuroscience professor at the university who is a team member. 

Some individuals who lost an arm or a leg or became unable to move them due to nerve damage often suffer from phantom pain in the limb, as if it was still attached.

The intense pain that derives from the imaginary or numb limbs cannot be handled with ordinary painkillers.

The condition is said to be occur because the patients' brains cannot properly process the fact they are no longer able to move their arms or legs freely.

To treat phantom pain, the researchers created left-right reversed images of the healthy arms of 12 patients, and asked them to attempt to move the "phantom arms."

The training system uses brain-computer interface (BCI) technology designed to operate computers with cerebral signals. When the same cerebral signal as that recorded when patients move their fully functioning arms is detected, the images of the phantom arms move under the BCI-based method.

The test subjects were told to evaluate their levels of pain following the three-day training program, and the scientists found that the level of pain dropped by 36 percent on average five days after the experiment.

The technique was as effective as a practice program in which patients' cerebral activity connected to phantom pain is strengthened by showing their movable limbs in mirrors to make them believe they have not lost a limb, according to the team.

Another trial that did not use the specific brain signals proved to be ineffective in easing patients' suffering.

As the BCI method's effects fade over time, the researchers are currently looking to develop new mechanisms to regularly offer training sessions and monitor brainwaves and other cerebral data for clinical applications.