This clinical trial is designed to assess the effectiveness of advanced neuromodulation techniques in reducing phantom limb pain by improving sensory feedback in bionic prostheses. The study will explore the use of Peripheral Nerve Stimulation to evaluate their impact on pain relief and sensory restoration. The trial aims the development of neuroprostheses that can provide sensory feedback through stimulation.
Amputation of the upper limb at the level of the forearm or upper arm, or amputation of the lower limb at the level of the lower leg or thigh.
Age between 18 and 65 years.
Duration since amputation is at least 6 months.
Presence of persistent chronic pain syndrome rated between 4 and 10 on the Visual Analog Scale (VAS).
Presence of severe somatic pathology that hinders surgical treatment and participation in the study.
Presence of psychiatric disorders (including a history of), severe depression, suicidal tendencies, or a history of suicide attempts.
Presence of severe orthopedic deformity in the limb above the level of amputation.
History of cancer.
Parallel
Peripheral Nerve Stimulation
Procedure/SurgeryPeripheral Nerve Stimulation (PNS) is a neuromodulation technique used to treat chronic pain. The procedure starts with a preoperative assessment, including imaging to identify the target peripheral nerve. Under local anesthesia, a thin, insulated electrode is implanted near the nerve, usually with the help of fluoroscopic or ultrasound guidance for precision.
Spinal cord stimulation
Procedure/SurgerySpinal Cord Stimulation (SCS) is a neuromodulation that involves the implantation of a device that delivers electrical impulses to the spinal cord through an electrode placed in the epidural space. The stimulation alters pain signals before they reach the brain, effectively masking or reducing the sensation of pain.
Dorsal Root Ganglion Stimulation
Procedure/SurgeryDorsal Root Ganglion Stimulation (DRGS) is a targeted neuromodulation technique for managing chronic pain. The procedure begins with a thorough preoperative assessment, including imaging to locate the specific dorsal root ganglion (DRG) associated with the pain. Under local anesthesia, a small electrode is implanted near the DRG. This is done through a minimally invasive procedure, often guided by fluoroscopy or CT imaging to ensure precise placement.
Motor Cortex Stimulation
Procedure/SurgeryMotor Cortex Stimulation (MCS) is a neuromodulation technique that involves the surgical implantation of electrodes over the motor cortex, typically targeting the precentral gyrus, to deliver electrical stimulation. The procedure involves placing an electrode grid or strip on the dura mater overlying the motor cortex, which is identified via neuroimaging techniques such as functional MRI or neuronavigation. Once implanted, the electrodes are connected to an implanted pulse generator (IPG), which delivers adjustable electrical impulses.
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Treatment groupsSee each treatment group below.
VAS
The Visual Analog Scale (VAS) is a 10 cm line used to measure pain intensity. One end of the line represents \"no pain,\" while the other end signifies \"worst possible pain.\" The line can be either horizontal or vertical.
SF-36
The questionnaire consists of 36 items grouped into eight scales: physical functioning, role limitations due to physical health, bodily pain, general health, vitality, social functioning, emotional well-being, and mental health. Each scale ranges from 0 to 100, where 100 represents full health. Higher scores indicate better quality of life, with two summary measures: physical and mental well-being.
DN 4
The DN4 (Douleur Neuropathique 4) questionnaire is a diagnostic tool designed to identify neuropathic pain, caused by nerve damage. It includes 10 items divided into two sections. The first part consists of seven questions that assess the patient's pain symptoms, such as burning, tingling, electric shocks, or numbness. The second part involves a clinical examination where the physician tests for reduced sensitivity to touch and pinprick, as well as pain response to light brushing. Each item is scored with 1 point for "Yes" and 0 for "No." A total score of 4 or higher indicates a high probability of neuropathic pain.
Sensory threshold change
In this task, the minimal amplitude of stimulation required to evoke a sensory response is experimentally determined. Numbers 1 and 2 appear on the screen, and at the moment one of the numbers appears, stimulation is simultaneously activated. The participant's task is to identify when the stimulation occurred and to input their response using the keyboard. After completing the task, a psychophysical curve will be computed, and the amplitude value that yields an accuracy of 0.75 will be used.
Agency
Self-report questionnaires where participants rate their sense of agency over the prosthesis during tasks. It uses 0 to 10 scale, where 0 means lower agency and 10 means higher agency
Embodiment
Throughout the study, participants will be asked to complete questionnaires assessing the degree of embodiment of the prosthesis. Since during the experimental sessions, feedback from the prosthesis is projected onto the phantom limb, the research team anticipates observing a transfer effect from the phantom limb to the robotic hand. The degree of this transfer will be evaluated using the Embodiment questionnaires for both upper and lower limbs. Embodiment uses scale from -9 to 9; -9 means "No embodiment" and 9 means "High embodiment".
Pain detect
The questionnaire is intended for completion by a physician and combines a pain distribution diagram with a visual analog scale (VAS) and a section focused on identifying spontaneous and triggered neuropathic pain symptoms. It also assesses the nature of pain using the diagram, categorizing it as constant, episodic, or constant with episodes, among others. The questionnaire comprehensively reflects all possible pain parameters, allowing for clear tracking of pain dynamics over time. The total score ranges from -1 to 38. Based on this score: ≤ 12: Neuropathic pain is unlikely. 13-18: The result is ambiguous; further assessment may be needed. ≥ 19: Neuropathic pain is likely.
Object detection
In a task that requires distinguishing object sizes using feedback from a prosthetic hand grasps objects made of different materials, of varying shapes, or of the same shape but with different diameters.
Visual-motor integration
The participant's task is to transport an object within designated zones using their prosthesis. In each trial, the target zone is randomly determined, and the participant must move the object to this zone as quickly and accurately as possible. The experimental conditions include sessions where neuroprosthetic feedback is active and others where the system is disabled. During the task, the participant wears eye tracking glasses. Investigators measure the number and duration of fixations on the prosthesis.
Value of sensory discrimination
Value of sensory discrimination is measured as Accuracy of Object Recognition. In this task, patients distinguish object sizes using feedback from stimulation through a prosthetic hand. The hand grasps objects made from various materials, with different shapes, or the same shape but different diameters. Concurrently, signals from the prosthetic sensors are translated into patterns of electrical stimulation. When the patient initiates a grasp, changes in the sensor signals result in adjustments to the amplitude of the neurostimulation. The patient\'s goal is to identify the properties of the objects based solely on the neurostimulation signals, while visual and auditory cues are blocked with a mask and headphones. It is expected that as patients adapt to the prosthetic system, their performance in recognizing objects will improve over time.
Grasping surface differentiation
In this task, the participant is presented with three identical objects, each assigned to one of three classes: (1) a non-tactile object, (2) a tactile object, and (3) a highly tactile object. At the start of each trial, the object classes are randomly reassigned. The distinction between the classes is that, upon touching an object of class (1) with the prosthesis, the participant receives no feedback; touching a class (2) object triggers low-amplitude stimulation, and a class (3) object triggers high-amplitude stimulation. During the trial, the participant uses the prosthesis to examine each object and determine which one belongs to class 2. As a final measurement investigators take the accuracy in this task.
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Skolkovo Institute of Science and Technology
Lead sponsor
Motorica LLC
Collaborator
The Federal Center of Brain Research and Neurotechnologies
Collaborator
