Phantom motor execution as a treatment for phantom limb pain: protocol of an international, double-blind, randomised controlled clinical trial | Eva Lendaro et al. | ResearchPod

Transcript: Phantom motor execution as a treatment for phantom limb pain: protocol of an international, double-blind, randomised controlled clinical trial

Alex: Does it matter whether you actually move a limb that isn't there, or just imagine moving it? A trial running across nine clinics is built to answer exactly that, for people living with phantom limb pain.

Sam: Phantom limb pain meaning pain felt in the amputated limb itself. Before we go further, place this for me. Whose work is it, and what kind of document?

Alex: It's a published trial protocol in BMJ Open from 2018, led by Eva Lendaro, with Max Ortiz-Catalan as corresponding author. So it's the plan for a double-blind, randomised trial, not the results. Nobody knows yet how it turned out, at least from this document.

Sam: A protocol is a hard sell for a busy listener. Why should someone outside pain research care?

Alex: Because the field has a quality problem. The authors note more than 60 treatments for phantom limb pain in the literature, but controlled trials are scarce and tend to be poor. This design isolates a single variable very cleanly. So we'll cover the idea behind the treatment, how the control is built, and how far the existing evidence goes.

Sam: Start with the treatment. What is phantom motor execution, in practice?

Alex: Electrodes sit on the skin of the residual limb. They pick up the muscles' electrical activity. Software then uses myoelectric pattern recognition, which means decoding the intended movement from those muscle signals. The decoded movement drives a virtual limb on screen, or a game, in real time.

Sam: Give me a concrete picture. What does a session actually look like for a patient?

Alex: A camera films the person and a virtual arm is superimposed where the missing arm would be. The patient tries to open and close their missing hand. If the decoder reads it, the virtual hand opens and closes. Difficulty climbs over the sessions by adding pairs of opposite movements, like hand open and close, or knee flex and extend.

Sam: Mirror therapy already gives people a moving image of the missing limb. What does this add?

Alex: The authors' point is verification. With a mirror, the patient can just move the healthy arm and the reflection still moves. You don't know whether they're engaging the phantom at all. Motor imagery, meaning imagining a movement without doing it, has mixed evidence. Some randomised studies suggest it can even increase pain. Decoding the muscle signals ensures that real motor commands are being produced.

Sam: And the theory for why execution should matter more?

Alex: The authors cite evidence linking phantom pain to maladaptive changes in the brain's sensory cortex. Their working hypothesis is that executing movements uses competing neuroplasticity, the brain's ability to rewire. They expect it to normalise brain and spinal circuits more fully than approaches that don't integrate sensory and motor information. That's framed as a hypothesis, not a demonstrated mechanism.

Phantom motor execution as a treatment for phantom limb pain: protocol of an international, double-blind, randomised controlled clinical trial

Eva Lendaro, Liselotte Hermansson, Helena Burger, Corry K Van der Sluis, Brian E McGuire, Monika Pilch, Lina Bunketorp-Käll, Katarzyna Kulbacka-Ortiz, Ingrid Rignér, Anita Stockselius, Lena Gudmundson, Cathrine Widehammar, Wendy Hill, Sybille Geers, Max Ortiz-Catalan

Jul 1, 2018·8:04·user_upload·Original Paper

Phantom limb painPhantom motor executionVirtual and augmented realityRandomised controlled clinical trialPhantom Limb Pain (PLP)Phantom Motor Execution (PME)

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8 min

Summary

Research Question

Phantom limb pain (PLP) is a chronic, often debilitating condition thought to be driven by maladaptive neuroplastic changes in the brain following amputation. Current treatments, including conventional motor imagery and mirror therapy, have shown limited or inconsistent success. This study tests the hypothesis that active, direct execution of phantom limb movements—enabled by machine learning and immersive virtual/augmented reality (VR/AR)—provides superior relief for PLP compared to passive motor imagery by better normalizing disrupted cortical and spinal motor circuits.

Study Approach

This is an international, multicentre, double-blind, randomised controlled trial involving 67 participants with upper or lower limb amputations. Participants are assigned in a 2:1 ratio to either the experimental group (PME) or an active control group (PMI). In both groups, participants engage with the same VR/AR systems and serious gaming environments. The critical difference is that the PME group uses myoelectric sensors to drive actual (though phantom) movement execution, while the PMI group monitors to ensure no muscle contraction occurs during the imagination process. The primary efficacy measure is the change in pain intensity on the Pain Rating Index (PRI) from baseline to the end of the 15-session treatment protocol.

Why It Matters

Because PLP is often resistant to traditional pain management, finding effective, non-pharmacological interventions is a high clinical priority. By using myoelectric pattern recognition to 'close the loop' on motor control, PME attempts to provide the brain with the sensory-motor feedback it lacks. This rigorous multicentre design, which includes long-term follow-ups at 1, 3, and 6 months, aims to provide high-quality evidence that could establish PME as a standard, technology-driven therapy for chronic phantom limb pain.

Key Terms and Definitions

Phantom Motor Execution (PME) — A therapeutic approach where a patient's volitional motor signals are decoded from residual limb muscles and used to control movements of a virtual limb in real-time.
Phantom Motor Imagery (PMI) — The control condition of the study, where patients mentally imagine moving their phantom limb without performing the muscular contractions associated with motor execution.
Myoelectric Pattern Recognition — The machine learning-based technology that identifies specific motor patterns (intended movements) from electrical signals recorded on the skin surface of the residual limb.
Pain Rating Index (PRI) — The primary efficacy endpoint derived from the Short-Form McGill Pain Questionnaire, used to quantify the intensity and quality of pain.
Maladaptive Plasticity — Brain reorganization occurring after amputation that is hypothesized to underlie the development and persistence of phantom limb pain.

Abstract

INTRODUCTION: Phantom limb pain (PLP) is a chronic condition that can greatly diminish quality of life. Control over the phantom limb and exercise of such control have been hypothesised to reverse maladaptive brain changes correlated to PLP. Preliminary investigations have shown that decoding motor volition using myoelectric pattern recognition, while providing real-time feedback via virtual and augmented reality (VR-AR), facilitates phantom motor execution (PME) and reduces PLP. Here we present the study protocol for an international (seven countries), multicentre (nine clinics), double-blind, randomised controlled clinical trial to assess the effectiveness of PME in alleviating PLP. METHODS AND ANALYSIS: Sixty-seven subjects suffering from PLP in upper or lower limbs are randomly assigned to PME or phantom motor imagery (PMI) interventions. Subjects allocated to either treatment receive 15 interventions and are exposed to the same VR-AR environments using the same device. The only difference between interventions is whether phantom movements are actually performed (PME) or just imagined (PMI). Complete evaluations are conducted at baseline and at intervention completion, as well as 1, 3 and 6 months later using an intention-to-treat (ITT) approach. Changes in PLP measured using the Pain Rating Index between the first and last session are the primary measure of efficacy. Secondary outcomes include: frequency, duration, quality of pain, intrusion of pain in activities of daily living and sleep, disability associated to pain, pain self-efficacy, frequency of depressed mood, presence of catastrophising thinking, health-related quality of life and clinically significant change as patient's own impression. Follow-up interviews are conducted up to 6 months after the treatment. ETHICS AND DISSEMINATION: The study is performed in agreement with the Declaration of Helsinki and under approval by the governing ethical committees of each participating clinic. The results will be published according to the Consolidated Standards of Reporting Trials guidelines in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT03112928; Pre-results.

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