New Research: Augmented Reality May Relieve Phantom Limb Pain
Interview with Paul F. Pasquina, MD, and Kiran V. Patel, MD Could “driving” a virtual race car around a track help ease the phantom limb pain that many amputees experience? A small study that focused on 14 patients found that moving and visualizing a phantom limb in augmented reality lessened phantom limb pain. The patients had started to suffer from phantom limb pain after having an arm amputated.
The new research, reported in an article published in The Lancet, found that, on average, the patients’ intensity, quality, and frequency of phantom limb pain was cut in half following a treatment involving augmented reality and serious gaming (video games designed for professional and military use). The study participants, all of whom underwent an arm amputation from 2 to 36 years ago, had not benefitted from previous treatments.
Asked whether this research offers hope to amputees who suffer from phantom limb pain, Assistant Professor Max Ortiz-Catalan, PhD, lead study author, in the Department of Signals and Systems, Chalmers University of Technology in Sweden, commented: “That’s the idea of the treatment. We are introducing it in clinics now.” He added, “We consider that our approach overcomes the technological limitations of previous treatments, and therefore is more likely to produce successful results.”
Paul F. Pasquina, MD, chair, Department of Physical Medicine and Rehabilitation F. Hebert School of Medicine, Uniformed Serves University of the Health Sciences, noted that: “Phantom limb pain continues to be a common problem for most individuals with acquired limb amputation, including many of our wounded soldiers.”
Commenting on the new research, Dr. Pasquina said, “I believe that we are now only beginning to scratch the surface of what advances in computer science will have on healthcare. This includes further applications of augmented reality and computer gaming. We have successfully utilized virtual reality in the care of multiple individuals with combat related injuries, including treating phantom limb pain. I look forward to further exploration in these rapidly expanding new technologies and embrace the cross-disciplinary collaboration that occurs between healthcare professionals, computer scientists and gaming innovators."
Using “phantom motor execution” with amputees who have phantom limb pain could improve their quality of life, said Kiran V. Patel, MD, director of neurosurgical pain at Lenox Hill Hospital in New York City and an interventional pain management physician at the Spine and Pain Institute of New York. Using a prosthesis can be difficult for a patient experiencing phantom limb pain. This can lead to depression since the person is then less functional.
“Historically, there has been a reliance on pain medications,” Dr. Patel said. “This new research is consistent with what we are seeing in other areas of pain management. We want to focus on non-invasive, non-pharmacological treatment and on a patient’s functionality. If you can perform the activities of daily living, like showering, cooking a meal, and washing clothes, this is a step in the right direction.”
How It Was Done
Study participants received 12 sessions of phantom motor execution that included using machine learning, augmented and virtual reality, and serious gaming. At the sessions, researchers placed sensors on the patients’ stumps in order to detect muscular activity for the missing limb. When fed into a computer that decoded them, the signals were then used to create an active virtual arm on a computer screen. This represented the patient’s missing arm.
In the therapy that followed, patients actually “trained” the virtual limb. Using their phantom movements and imitating the movements of an on-screen limb, they “drove” a virtual car around a track during 12, 2-hour treatment sessions. This “phantom motor execution” is similar to mirror therapy, which makes use of reflections of an unaffected limb so that it appears in the mirror that the person is moving their missing limb. The individual can then “move” the limb out of positions that may be painful. Still, mirror therapy is not always effective.
Virtual Reality: A Promising Treatment
Phantom motor execution appears to be a promising treatment. With the augmented reality and serious gaming that characterize this therapy, there was a 32% reduction in the intensity of the pain (from an average rating of 5.21 out of 10 on the numeric rating scale [NRS] prior to treatment to 3.57 at the final treatment session). Additionally, researchers found that the study subjects had a 51% reduction in pain quality and intensity, going from 19.4 to 9.7 out of 75 on the pain rating index (PRI). There also was a 47% reduction in the duration, frequency, and intensity of pain, reduced from 2.24 to 1.25 out of 5 on the weighted pain distribution (WPD), according to the Lancet article.
In activities of daily living and sleeping, the NRS score for intrusion of phantom limb pain decreased by 43% (SD 37; absolute mean change 2·4 [2·3]; P=0·004) and 61% (39; absolute mean change 2·3 [1·8]; P=0·001), respectively. Two of 4 study participants who took medication for their pain reduced their intake by 81% (absolute reduction 1,300 mg, gabapentin) and 33% (absolute reduction 75 mg, pregabalin). These improvements held steady for 6 months after the last treatment, according to the investigators.
The new treatment would need to be approved by the Food and Drug Administration and undergo randomized clinical trials before becoming widely available, Dr. Patel noted. Overall, this treatment could be a real breakthrough in the treatment of phantom limb pain, she said. It also raises the possibility as to whether a similar therapy could be used for other conditions, she says. “It suggests that neural networks can be accessed because these patients had less pain when they could retrain what their bodies were sensing,” Dr. Patel said. “There may be other ways that we could use this to our advantage to treat other conditions.”