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Augmented reality used to treat phantom limb pain

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14 trial participants reported a 50% decrease in pain towards the conclusion of the study

Researchers at Chalmers University of Technology in Sweden have developed a method of treating phantom limb pain using augmented reality and machine learning.

The clinical trial was conducted on 14 arm amputees with chronic phantom limb pain. The treatment that lasted 12 sessions reduced their pain by approximately 50%, according to a clinical study published in The Lancet.

People who lose an arm or leg often experience phantom limb pain, as if the missing limb was still there. Phantom limb pain can become a serious chronic condition that significantly reduces the patients’ quality of life. It is still unclear why phantom limb pain and other phantom sensations occur.

The method consists of using muscle signals from the amputated limb to control augmented and virtual environments. Electric signals in the muscles are picked up by electrodes on the skin. Artificial intelligence algorithms translate the signals into movements of a virtual arm in real-time. The patients see themselves on a screen with the virtual arm in the place of the missing arm, and they can control it as they would control their biological arm.

This allows the patient to reactivate areas of the brain that were used to move the arm before it was amputated, which might be the reason that the phantom limb pain decreases. The method is non-invasive and any side effects have yet to surface.

Dr Ortiz Catalan, researcher at the university, said: “We selected the most difficult cases from several clinics. We wanted to focus on patients with chronic phantom limb pain who had not responded to any treatments. They had been experiencing phantom limb pain for an average of 10 years.”

The intrusion of pain in sleep and activities of the daily living was reduced by half, according to the university. In addition, two patients who were on analgesics were able to reduce their doses by 81% and 33%.

Catalan added: “In our study, we also saw that the pain continuously decreased all the way through to the last treatment. The fact that the pain reduction did not plateau suggests that further improvement could be achieved with more sessions.”

The researchers are now planning a larger clinical trial that will consist of 30 patients from different countries, including leg amputees, and will involve more sessions with the aim to eliminate the pain completely.

The technology is in the process of being commercialised by the Gothenburg-based company Integrum. The researchers believe that the technology could also be used for other patient groups who need to rehabilitate their movement capability, for example after a stroke, nerve damage or hand injury.
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