7 iun. 2025
Teodora Gheorghe
Recording Spinal Neural Activity: A Foundational Step Toward Neural-Controlled Lower-Limb Exoskeletons
As part of the NerveRepack project, a significant step was recently achieved by the medical team at the University of Medicine and Pharmacy (UMF) in Bucharest, through a surgical procedure dedicated to the real-time acquisition of spinal motor nerve signals. This experimental intervention, performed on a patient with no spinal injury, is essential for characterizing the electrophysiological properties of motor neural signals responsible for lower limb movement. The results will serve as the scientific basis for the development of a laboratory prototype of a neurally controlled exoskeleton.
Context and Scientific Motivation
In patients with lower-limb paralysis, damage to the spinal cord disrupts the transmission of motor commands from the brain to the muscles of the legs. While exoskeletons currently available on the market assist in gait rehabilitation or ambulation, they are typically operated through manual commands or pre-programmed movement patterns. These systems lack a direct interface with the patient’s nervous system and do not reflect the user’s natural motor intent.
The objective of this experimental procedure was to acquire authentic motor signals from healthy spinal nerves in order to understand their structure, frequency, amplitude, and duration. These parameters are essential for designing a control module capable of decoding such signals and converting them into commands for an exoskeleton’s actuation system.
Surgical Procedure Overview
The intervention was performed on the spinal region and involved the exposure of specific spinal motor nerves responsible for transmitting commands to lower-limb muscles. During the procedure, no electrodes were implanted. Instead, specialized probes were temporarily inserted into the vicinity of the target nerves.
Using a precision acquisition system, neural activity was recorded from several spinal nerves. The collected signals represent the electrical impulses that naturally travel toward the leg muscles in healthy individuals. These signals are key to enabling natural, voluntary movement, and their analysis provides a reference framework for replication in assistive technologies.
Technical Description of the Procedure
The surgical team performed the procedure under general anesthesia, with the patient positioned laterally to expose the lumbar spine. A posterior approach was used to access the spinal nerves located in the lumbar plexus. Following dissection and isolation of the nerve roots, several motor nerves innervating lower-limb muscles were identified. To avoid tissue damage while ensuring signal quality, high-impedance monopolar recording probes were inserted carefully near the nerves without penetrating them. Neural activity was recorded during controlled stimulation of leg muscles to verify the correspondence between signal patterns and muscle response. Data were sampled at high resolution using a multichannel neural acquisition system, capturing both spontaneous and evoked potentials.
Scientific and Technical Impact
The data obtained from this procedure are among the first of their kind and provide concrete experimental evidence on the characteristics of real motor signals originating in the spinal nerves. These recordings will directly inform the development of the NerveRepack exoskeleton’s control architecture, which aims to interpret the user’s neural commands in real time.
Unlike commercially available exoskeletons for patients with lower-limb paralysis, which are operated similarly to machines (via joysticks, buttons, or pre-set gait cycles), the NerveRepack concept envisions a system that responds to the user’s own nervous signals. In this paradigm, motor intention is not mimicked—it is truly captured and transmitted, offering a fundamentally different and potentially transformative approach to movement restoration.
Next Steps in Development
The data collected during the surgical session are currently undergoing detailed signal analysis and classification. These results will serve as the basis for developing decoding algorithms and hardware modules capable of interpreting spinal neural signals in a laboratory environment.
Importantly, the NerveRepack project does not aim to perform invasive implantation of neural interfaces at the spinal level in patients during the current phase. Instead, the immediate goal is to design and test a lab-scale prototype exoskeleton system controlled by pre-recorded, biologically accurate signals.
The surgical acquisition of spinal neural motor signals represents a foundational milestone for the NerveRepack project’s work on neurally controlled lower-limb exoskeletons. This intervention offers, for the first time within the project, a precise understanding of the electrophysiological signals that drive natural leg movements. By grounding the control of assistive technologies in authentic motor signals, NerveRepack moves closer to developing exoskeleton systems that align with the physiological and cognitive capabilities of users.
