A new publication co-authored by Dr. Todd Kuiken, MD, PhD describes how a surgical procedure developed to enhance prosthesis control may also reduce post-amputation pain. The article, Targeted muscle reinnervation treats neuroma and phantom pain in major limb amputees: a randomized clinical trial, was published in Annals of Surgery, a peer-reviewed journal that focuses on advances in surgical science and practice.
What is a neuroma pain?
A neuroma is a painful growth of nerve tissue that develops at the end of cut or damaged nerve endings in the residual (amputated) limb. An estimated 10 to 76% of people with limb loss experience pain in their amputated limb.
Some very archaic methods of treating neuromas included hitting the area with a piece of wood. These days, neuromas are treated with medication or other therapeutic options, such as massage or acupuncture. Surgery to remove the neuroma is also an option, but conventional surgical procedures are not always successful because there is a chance for the neuroma to return.
What is phantom limb pain?
Phantom limb pain is another form of pain that describes feelings in the area where the limb is missing. The pain may feel like tingling sensations, burning, electric shocks, hot or cold, or a feeling of numbness. Reasons why phantom limb pain occurs are not fully understood, but research suggests it may be due to the reorganization of the brain that occurs after amputation.
What is Targeted Muscle Reinnervation?
Targeted Muscle Reinnervation, or TMR for short, is a surgical procedure developed by Drs. Todd Kuiken, MD, PhD, and Gregory Dumanian, MD of Northwestern University. The procedure involves a series of nerve transfers to “reassign” the nerves to new target muscles.
The initial goal of the TMR procedure was to create additional control sites for myoelectric prostheses, which are controlled through small electrical signals (electromyography or EMG) that are generated on the surface of the skin when a muscle contracts. During early studies with TMR, researchers observed that in addition to improving prosthesis control, TMR also appeared to reduce amputation pain.
The goal of this study was to investigate the potential of using TMR to reduce neuroma and phantom limb pain in a formal clinical trial involving 28 individuals with limb loss above the wrist or ankle.
What did the researchers find?
Researchers found that TMR improved pain compared to conventional surgical methods. Current surgical methods involve excising the neuroma and transposing the remaining nerve bundle into bone, fat, vein, or sometimes back onto itself. In contrast, with TMR, major and sensory nerves are channeled toward specific nerve receptor targets, typically a muscle in the residual limb.
The authors theorized that TMR treats the pain by essentially closing a feedback loop. In other words, as Dr. Dumanian explains, it gives the nerves “somewhere to go and something to do,” which essentially heals the nerve ending instead of just “hiding” it.
The authors state that future studies will focus on refining the procedure, as well as investigating the impact of TMR for specific patient populations who are at high risk of limb loss (e.g., people with vascular disease).
Takufumi Yanagisawa, Ryohei Fukuma, Ben Seymour, Koichi Hosomi, Haruhiko Kishima, Takeshi Shimizu, Hiroshi Yokoi, Masayuki Hirata, Toshiki Yoshimine, Yukiyasu Kamitani, Youichi Saitoh. Induced sensorimotor brain plasticity controls pain in phantom limb patients. Nature Communications, 2016; 13209 DOI: 10.1038/ncomms13209