A group of researchers at the University of Tokyo and their collaborators showed that using a virtual reality system to treat phantom limb pain by creating the illusion that patients are moving their absent limbs by will and having them repeat this exercise helped ease their perceived pain.
Phantom limb pain is a curious phenomenon in which patients who have lost the sense of feeling in arms and legs that no longer exist due to amputations, or that are no longer capable of receiving sensory input because of injury or damage to the nervous system, perceive painful sensation in their absent limbs.
Patients can actually create images in the brain and imagine moving their phantom limbs, but many who suffer from phantom limb pain lack this ability, called movement representation, and experts believe this brings on the pain. Conventional treatments also have been unable to adequately relieve the pain.
The joint group of researchers led by Associate Professor Masahiko Sumitani of the Department of Pain and Palliative Medicine at the University of Tokyo Hospital tested whether the patients’ pain improved when they underwent studies with a virtual reality (VR) system that created the illusion that they were exercising their phantom limbs on their own volition. Prior to this study, researchers used a method called bimanual circle line coordination task to evaluate and quantify the onset of movement representation. They not only found that adopting VR alleviated phantom limb pain, but that a strong correlation existed between movement representation and pain relief.
The VR system developed by the research group creates a moving mirror image of the intact, healthy opposite limb using motion capture technology, and projects that image in real time onto a head-mounted display. The goggle-like display that the patients wear on their heads allows them the virtual illusory experience of exercising their phantom limb at will when they move their healthy limb.
The current outcome not only demonstrated that the mechanism causing phantom limb pain is rooted in the disruption of movement representation in the brain, but also succeeded in proposing a novel brain treatment for phantom limb pain using VR.
“I became a pain researcher because I’ve had adverse reactions to pain from the time I was a child. Pain can really put one in a foul mood,” says Sumitani. He continues, “Neuropathic pain is the most severe condition among chronic pain diseases, which many patients still suffer from. Our present findings successfully revealed the underlying mechanism of neuropathic pain and offers a novel treatment strategy for patients with not only phantom limb pain after either amputation or brachial plexus avulsion injury, but also post-spinal cord injury pain and thalamic pain.”
This study was supported by the Japan science ministry’s Grants-in-Aid Project under the Scientific Research on Innovating Areas category as “Constructive Developmental Science” research, and published in the European Journal of Pain online edition on July 5, 2016 (Japan time).
Professor Yasuo Kuniyoshi, Intelligent Systems and Informatics Laboratory, Department of Mechano-Informatics, Graduate School of Information Science and Technology, the University of Tokyo; Associate Professor Shin-ichiro Kumagaya, Research Center for Advanced Science and Technology, the University of Tokyo; and Project Assistant Professor Michihiro Osumi, Neurorehabilitation Research Center, Kio University, contributed to this research.