Stinging, tingling, twitching. After an amputation, it is not uncommon for pain to occur in the missing body part. The phenomenon of phantom limb pain still poses unanswered questions for medicine and science. In many cases, the drugs used are not very effective. We think it is time to explore new treatment methods.
It is estimated that 50-80% of all amputees experience phantom limb pain during their lifetime. The direct cause remains unknown. However, recent studies using functional magnetic resonance imaging (fMRI) suggest that phantom limb pain after amputation may be caused by poor reorganization of pain pathways in the brain. It is thought that therapies aimed at restructuring the pain pathways may provide pain relief.1
One example of such a therapy is the use of virtual reality (VR). This is a computer-generated reality that is transmitted three-dimensionally in designated rooms or via special VR goggles. In the case of an amputee patient, virtual reality can be used to simulate movements of the missing limb. To do this, an image of the missing limb is projected into the VR environment. The patient must now solve various tasks with his virtual hand. Muscle contractions in the residual limb, which are detected by a sensor wristband, can be used to control the movement of the virtual hand.
Acting in a virtual reality causes the patient to increasingly identify with the fictitious world or to immerse himself in an illusory world in which he has two healthy hands.
There are various approaches that explain why virtual reality can alleviate pain. For example, as part of a study on burn injuries, it was discovered that when VR was used, there was less activation of the brain regions where pain sensation originates. In this case, virtual reality acted as a "distraction" from the acute, intense pain.
For chronic pain such as phantom limb pain, it is thought that virtual reality can rearrange the pain pathways in the brain that have been destroyed by an amputation. Mirror therapy inventor Vilayanur S. Ramachandran suspects that after an amputation, the brain still sends signals to the missing limb, but no signals are sent back to the brain from there. He concludes that phantom limb pain occurs because the brain is confused by the missing signals and cannot adapt to the physiological change in the body.6
The idea behind mirror therapy and VR therapy is that just seeing a virtual limb helps retrain the brain areas responsible for body perception (somatosensory cortex).7
In other words: When the patient sees and moves the virtual hand, his or her brain receives the signal that a hand is present - which in turn reorganizes the pain pathways in the brain that have been destroyed (the neurons re-link).
The brain thus restores the muscle signals sent when the virtual hand is moved. In this way, a new image of the hand is gradually created in the brain: the image of a healthy hand without pain.
VR therapy for the treatment of phantom limb pain is still relatively new. Nevertheless, scientific studies already show that it has the potential to reduce the intensity of phantom limb pain and to have both short- and long-term effects on pain reduction.2-5
In addition, participants in a study on virtual reality for phantom limb pain patients report that they find the therapy realistic, helpful, and entertaining, and are satisfied with the outcome.5 Moreover, due to its effectiveness in practice and the high degree of individualization, numerous experts endorse VR therapy for phantom limb pain treatment.1
Pohlig and the DLR (German Aerospace Center) are working together on a research project that investigates virtual reality as a suitable therapy method for phantom limb pain patients who have had their arms amputated.
In order to be able to carry out the study, we are looking for patients to support us. If you suffer from phantom limb pain and would like to try VR therapy, please contact us! One session lasts 60 min and takes place approximately two to three times per week. The therapy lasts 4-6 weeks.
In our daily lives, we rely on the use of our hands. Cars, smartphones, electrical appliances: everything works by finger touch or hand grip. Therefore, even a partial loss of hand or arm function can lead to impairments in social and professional life, phantom limb pain or depression.
After an amputation, virtual reality (VR) can provide useful services in the context of rehabilitation: for people with upper limb limitations, entering a virtual environment is a promising technology that can even alleviate phantom limb pain. The central starting point of VR therapy is to engage users in a virtual world through games and activities (immersion), where they can experience their missing or impaired limbs fully functioning again.
To detect what actions the amputee user wants to perform in the virtual environment, he wears a sensor bracelet on his residual limb. Inside, an adaptive system converts muscle signals into control commands for a virtual replica of the corresponding limb. Both the user and the therapist can teach the system new patterns at any time, correcting unstable signals or making adjustments to new actions.
In the virtual environment (e.g. in a kitchen, as a car driver or cyclist on the street etc.) the user can control a fully functional representation of his impaired limb. Control of the intended movement is based on the user's own muscle signals. The learning system recognizes the signals and enables intuitive gesture control, which is used to estimate both the type of gesture and the grasping force. Through the effect of immersion, a trust in the virtual limb is created.
The goal of the VVITA research project is to recruit patients, have them perform the desired exercises in virtual reality, and then collect data and statistics to clearly demonstrate the effectiveness of the approach in the selected application areas (phantom limb pain treatment, rehabilitation, prosthesis use training, etc.).
Source: German Aerospace Center (DLR) Institute of Robotics and Mechatronics.
Image credit: DLR (CC BY-NC-ND 3.0)
List of sources
1. Limakatso, K., & Parker, R. (2021). Treatment Recommendations for Phantom Limb Pain in People with Amputations: An Expert Consensus Delphi Study. https://doi.org/10.1002/pmrj.12556
2. Kulkarni, J., Pettifer, S., Turner, S., & Richardson, C. (2020). An investigation into the effects of a virtual reality system on phantom limb pain: a pilot study. British Journal of Pain, 14(2), 92. https://doi.org/10.1177/2049463719859913
3. Osumi, M., Inomata, K., Inoue, Y., Otake, Y., Morioka, S., & Sumitani, M. (2019). Characteristics of Phantom Limb Pain Alleviated with Virtual Reality Rehabilitation. Pain Medicine, 20(5), 1038–1046. https://doi.org/10.1093/PM/PNY269
4. Rutledge, T., Velez, D., Depp, C., McQuaid, J. R., Wong, G., Jones, R. C. W., Atkinson, J. H., Giap, B., Quan, A., & Giap, H. (2019). A Virtual Reality Intervention for the Treatment of Phantom Limb Pain: Development and Feasibility Results. Pain Medicine (United States), 20(10), 2051–2059. https://doi.org/10.1093/PM/PNZ121
5. Lendaro, E., Hermansson, L., Burger, H., van der Sluis, C. K., McGuire, B. E., Pilch, M., Bunketorp-Käll, L., Kulbacka-Ortiz, K., Rignér, I., Stockselius, A., Gudmundson, L., Widehammar, C., Hill, W., Geers, S., & Ortiz-Catalan, M. (2018). Phantom motor execution as a treatment for phantom limb pain: Protocol of an international, double-blind, randomised controlled clinical trial. BMJ Open, 8(7). https://doi.org/10.1136/BMJOPEN-2017-021039
6. Ramachandran, V.S. & Rogers-Ramachandran D. (1996). Synaesthesia in phantom limbs induced with mirrors. Proceedings of the Royal Society B: Biological Sciences, 22(263), 377-386.
7. Hoffman, H. G., Boe, D. A., Rombokas, E., Khadra, C., LeMay, S., Meyer, W. J., Patterson, S., Ballesteros, A., & Pitt, S. W. (2020). Virtual reality hand therapy: A new tool for nonopioid analgesia for acute procedural pain, hand rehabilitation, and VR embodiment therapy for phantom limb pain. Journal of Hand Therapy, 33(2), 254–262. https://doi.org/10.1016/j.jht.2020.04.001
Weitere Infos: Nissler, C., Nowak, M., Connan, M., Büttner, S., Vogel, J., Kossyk, I., & Castellini, C. (2019). VITA—An everyday virtual reality setup for prosthetics and upper-limb rehabilitation. Journal of neural engineering, 16(2), 026039. https://iopscience.iop.org/article/10.1088/1741-2552/aaf35f/meta