Phantom movements in augmented reality helps patients with intractable phantom limb pain

December 1, 2016, Chalmers University of Technology
In the augmented reality environment, the patients can see themselves on a screen with a superimposed virtual arm, which is controlled by muscle signals from their arm stump. Credit: Ortiz-Catalan et al., The Lancet, 2016.

Dr Max Ortiz Catalan at Chalmers University of Technology has developed a novel method of treating phantom limb pain using machine learning and augmented reality. This approach has been tested on over a dozen of amputees with chronic phantom limb pain who found no relief by other clinically available methods before. The new treatment reduced their pain by approximately 50 per cent, reports a clinical study published in The Lancet.

People who lose an arm or leg often experience , 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.

Several medical and non-medical treatments have been proposed to alleviate phantom limb pain. Examples include mirror therapy, various types of medications, acupuncture, and implantable nerve stimulators. However, in many cases nothing helps. This was the situation for the 14 arm amputees who took part in the first clinical trial of a new treatment, invented by Chalmers researcher Max Ortiz Catalan, and further developed with his multidisciplinary team in the past years.

"We selected the most difficult cases from several clinics," Dr Ortiz Catalan says. "We wanted to focus on patients with chronic phantom limb pain who had not responded to any treatments. Four of the patients were constantly medicated, and the others were not receiving any treatment at all because nothing they tried had helped them. They had been experiencing phantom limb pain for an average of 10 years."

Credit: Ortiz-Catalan et al., The Lancet, 2016.

The patients were treated with the new method for 12 sessions. At the last session the intensity, frequency, and quality of pain had decreased by approximately 50 per cent. The intrusion of pain in sleep and activities of the daily living was also reduced by half. In addition, two of the four patients who were on analgesics were able to reduce their doses by 81 per cent and 33 per cent.

"The results are very encouraging, especially considering that these patients had tried up to four different treatment methods in the past with no satisfactory results," Ortiz Catalan says. "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."

Ortiz Catalan calls the new method "phantom motor execution". It consist 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.

Thus, the perceived phantom arm is brought to life by a virtual representation that the patient can see and control. 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 decrease. No other existing treatment for phantom limb pain generates such a reactivation of these areas of the brain with certainty. The research led by Ortiz Catalan not only creates new opportunities for clinical treatment, but it also contributes to our understanding of what happens in the brain when occurs.

Max Ortiz Catalan demonstrates the augmented reality environment in his new Biomechatronics and Neurorehabilitation Laboratory at Chalmers University of Technology in Sweden. Credit: Anna-Lena Lundqvist

The clinical trial was conducted in collaboration with Sahlgrenska University Hospital in Gothenburg, Örebro University Hospital in Örebro, Bräcke Diakoni Rehabcenter Sfären in Stockholm, all in Sweden, and the University Rehabilitation Institute in Ljubljana, Slovenia.

"Our joint project was incredibly rewarding, and we now intend to go further with a larger controlled clinical trial," Ortiz Catalan says. "The control group will be treated with one of the current treatment methods for pain. This time we will also include leg amputees. More than 30 patients from several different countries will participate, and we will offer more treatment sessions to see if we can make the pain go away completely."

The technology for phantom motor execution is available in two modalities - an open source research platform, and a clinically friendly version in the process of being commercialised by the Gothenburg-based company Integrum. The researchers believe that this 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.

Explore further: Phantom limb pain relieved when amputated arm is put back to work (w/ Video)

More information: "Phantom motor execution facilitated by machine learning and augmented reality as treatment for phantom limb pain: a single group, clinical trial in patients with chronic intractable phantom limb pain." The Lancet, DOI: 10.1016/S0140-6736(16)31598-7

Related Stories

Phantom limb pain relieved when amputated arm is put back to work (w/ Video)

February 25, 2014
Max Ortiz Catalan, researcher at Chalmers University of Technology, has developed a new method for the treatment of phantom limb pain (PLP) after an amputation. The method is based on a unique combination of several technologies, ...

Phantom limb pain relieved when amputated arm is put back to work

March 10, 2014
People who lose an arm or a leg often experience phantom sensations, as if the missing limb were still there. Seventy per cent of amputees experience pain in the amputated limb despite that it no longer exists.

Cause of phantom limb pain in amputees, and potential treatment, identified

October 27, 2016
Researchers have discovered that a 'reorganisation' of the wiring of the brain is the underlying cause of phantom limb pain, which occurs in the vast majority of individuals who have had limbs amputated, and a potential method ...

Easing "phantom limb" pain

November 26, 2015
Amputees sometimes experience shooting pains or burning sensations in limbs that are no longer there. These sensations seem to originate in the spinal cord and brain, perhaps because neural pathways are receiving mixed signals ...

New study aimed at diminishing phantom pain suffered by amputees

April 27, 2015
A new clinical trial conducted by Emory Saint Joseph's Hospital interventional radiologist J. David Prologo, MD is studying a minimally invasive investigational treatment known as cryoablation therapy, hoped to help relieve ...

Minimally invasive treatment could freeze out phantom limb pain

April 6, 2016
A pioneering technique significantly reduces phantom limb pain—chronic pain emanating from the site of amputated limbs—according to findings presented at the Society of Interventional Radiology's 2016 Annual Scientific ...

Recommended for you

Mutations, CRISPR, and the biology behind movement disorders

November 12, 2018
Scientists at the RIKEN Center for Brain Science (CBS) in Japan have discovered how mutations related to a group of movement disorders produce their effects. Published in Proceedings of the National Academy of Sciences, the ...

In live brain function, researchers are finally seeing red

November 12, 2018
For years, green has been the most reliable hue for live brain imaging, but after using a new high-throughput screening method, researchers at the John B. Pierce Laboratory and the Yale School of Medicine, together with collaborators ...

Concussion tied to suicide risk

November 12, 2018
(HealthDay)—People who have experienced either a concussion or a mild traumatic brain injury are twice as likely to commit suicide than others, a new review suggests.

Autism is associated with zinc deficiency in early development—now a study links the two

November 9, 2018
The emergence of autism in children has not only been linked to genes encoding synaptic proteins—among others—but also environmental insults such as zinc deficiency. Although it is unclear whether zinc deficiency contributes ...

Scientists solve century-old neuroscience mystery—answers may lead to epilepsy treatment

November 9, 2018
Scientists at the Virginia Tech Carilion Research Institute have solved a 125-year-old mystery of the brain, and, in the process, uncovered a potential treatment for acquired epilepsy.

Researchers identify the neural basis of threatening and aggressive behaviors in Drosophila

November 9, 2018
You can always tell when two guys are about to get into a fight. It starts with angry stares, puffed-out chests, arms tossed out to the side, and little, aggressive starts forward. Neuroscientists call the combination of ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.