Master thesis presentation: Prediction of motor volition in the lower limbs: Towards a treatment for phantom limb pain

On Friday 26 August, 2016 Eva Lendaro, MPBME, will present her master thesis with the title “Prediction of motor volition in the lower limbs: Towards a treatment for phantom limb pain”.

When? Friday, August 26th at 14.00

Where? Landahlsrummet (room 7430), Hörsalsvägen 11, 7th floor, Chalmers

Examiner: Sabine Reinfeldt
Supervisor: Max Ortiz Catalan

Introduction: Immediately after an amputation, patients commonly experience the vivid sensation that the amputated limb is still present. However, quite often the awareness of a phantom limb is also accompanied by persistent pain. The mechanisms underlying this condition, known as phantom limb pain (PLP), are not completely understood and many different treatment strategies have been proposed with limited results. PLP has been found repeatedly correlated to the changes taking place in the sensorimotor cortex after the loss of the limb, and a newly introduced rehabilitation treatment, which attempts to reverse these changes by training the patient to move the phantom limb, has shown promising results. The system promotes motor execution via Augmented Reality (AR), Virtual Reality (VR) and gaming, which are controlled by phantom motions decoded using myoelectric pattern recognition (MPR). The technology has been tested on upper limb amputees suffering from chronic PLP with good outcomes. However, since lower limb amputations are more frequent, it is necessary to also demonstrate the technology in the lower limbs. The goal of this master’s thesis work was to translate the aforementioned treatment to the lower limb in order to test its effectiveness on subjects with trans-femoral amputation.

Methods: The work started by investigating the feasibility of MPR in the lower limb for both healthy and amputee subjects. In order to overcome the difficulties of recording myoelectric signals from the lower limb, different methodologies for placing the electrodes over thigh muscles were compared in terms of their performance in classifying non-weight bearing movements. The results of the study were applied to the MPR/VR treatment and used to treat one patient with trans-femoral amputation suffering from PLP. The patient, amputated 35 years earlier and suffering from constant and intense PLP, was treated at the “Centre for the Advanced Reconstruction of Extremities (C.A.R.E.)” at Sahlgrenska University Hospital, approximately twice a week for a total of 25 sessions.

Results: The preferred electrode configuration was identified among the ones compared and then adopted for the MPR/VR therapy. Furthermore, the new recording technique makes also the electrode placement easier, which is essential in the perspective of a technology use by clinicians and patients. The subject, who could not find relief with any previous therapy, experienced a significant decrease in pain at the end of the treatment.

Conclusion: This work identifies a preferred methodology for acquiring EMG signals to be used to treat PLP and demonstrate the effectiveness of the MPR/VR therapy on one PLP patient. The positive results, despite being limited to a single patient, justify further investigation in a wider study.