SERIES (1): Relieving phantom pain with virtual reality

PROMPT research project tests mix of prostheses and virtual reality gaming
18 January 2022
Eintauchen in virtuelle Welten, VRHQ, 13.1.

Phantom limb pain can prove a struggle for many amputees. They have endured the loss of a leg or arm, but their brain has yet to process the message properly. "On a scale of zero to ten, most sufferers rank their phantom pain at six to eight," according to Meike Annika Wilke, Professor of Mathematics and Computer Science at the HAW Hamburg’s Faculty of Life Sciences. Conventional treatment has only had limited success. To alleviate pain, the professor and other universities and companies all over Germany are now researching other forms of therapy involving the playful use of virtual reality (VR).

VR experiences prompt real reactions

Virtual reality has made strides and is now leading to real physical reactions. Virtual sensory impressions perceived by the brain are so real that arachnophobes perspire and suffer palpitations just by touching a creepy-crawly in a VR environment. The "Prosthetics and Orthotics for Mobile and Specific Phantom and Deafferentation Pain Therapy" (PROMPT) now aims to take advantage of that effect.

Many amputees use prostheses controlled by electrical muscle activity based on their remaining nerves. Built-in microvibrators or somatosensory feedback on personal body perception will be provided as part of PROMPT. Various VR games and experiences are used to train the sufferer's sensory perception.

Professor Meike Annika Wilke, Faculty of Life Sciences, HAW Hamburg
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Professor Meike Annika Wilke, Faculty of Life Sciences, HAW Hamburg

VR as continuation of mirror therapy

Amputees without an arm and who suffer from phantom pain or people whose arm is paralysed e.g., because the arm's  nerves were severed after a motorbike accident are at centre of PROMPT. An interruption of the nerves results in deafferentation, which is combated with VR. The arm becomes healthy and supple and patients are given various tasks. "They reach into water and set it in motion, stack dice or throw and catch balls and always with both hands," Wilke explained. The VR approach is thus a continuation of mirror therapy. A mirror is placed in front of the patient so that movements of the healthy arm are mirrored and perceived as movements of the affected arm.

Test persons needed 

Both therapy approaches try to trick the brain. Wilke remarked: "Research on phantom and deafferentation pain assumes that the cause could lie in a sensorimotor incongruence." The brain sends the command "move the arm", which is impossible because of the missing limb and there is no visual and sensory feedback. That results in an error message, so to speak. Enter VR: The virtual experience gives the brain the expected feedback and the number of error messages decrease and so does the pain. "That's the theory. However, the effect has not yet been proven. This is still a feasibility study." To come up with more long-term results and to verify their theory, researchers are now keen on finding test persons to take part in studies all over Germany. Wilke stressed: "People suffering pain after lower or upper arm amputations or arm paralysis are welcome to contact us on promptstudie@gmail.com."

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PROMPT Project

The German Ministry of Education and Research is putting EUR 2.4 million in funds towards the three-year research project. Apart from HAW Hamburg, its partners include the Clinic for Trauma Surgery, Orthopaedics and Plastic Surgery at the University Medical Center Göttingen, Clinical Psychology at the University of Jena, the 3D scan developer, Botspot, the Ottobock prosthesis manufacturer and Routine Health GmbH.