Phantom limb pain, where a person feels pain in an absent limb or a portion of a limb, is a very real phenomenon, most commonly experienced after amputation of an arm or leg. Chronic phantom pain is believed to affect around 10-45% of amputees. It is highly therapy resistant and can last for years, or even a lifetime, despite high dosages of painkillers that put patients at risk of addiction. However, hope may be on the horizon thanks to a modified hand prosthesis which enables feedback between the artificial hand and the brain.

Phantom pain is believed to occur because the brain structures that were originally responsible for the stimulus processing of the arm are suddenly "out of work" after the loss of the limb. This induces a functional reorganization of the affected brain regions according to Professor Dr Thomas Weiss from the Department for Biological and Clinical Psychology at Friedrich-Schiller-University Jena.

"These areas take over the processing of sensory stimuli from other body parts, especially the arm stump and the face," says Weiss. As a result intensified and sometimes painful sensations occur – the phantom pain.

Weiss's team from the University of Jena has been working with trauma surgeons from the Jena University Hospital to develop the new prosthetic device designed to address this problem. Pressure sensors between the thumb and index finger as well as on the thumb of the hand prosthesis transmit sensory information from the hand to a stimulation unit connected to the upper arm via a cuff. The brain picks up the feedback from the prosthesis as if it was the patient's own hand.

The team believes that feedback between the artificial hand and the brain, provided by the Jena system may play a part in preventing or reversing the reorganization of the brain.

"We would like to know if the transmission of sensory information from the hand is helpful to only a few people or if it is a therapeutic for all wearers of artificial limbs," explains Professor Weiss.

The team will now test the feedback system on as many patients as possible.

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