Sciatic nerve | EPFL Graph Search

The sciatic nerve, also called the ischiadic nerve, is a large nerve in humans and other vertebrate animals which is the largest branch of the sacral plexus and runs alongside the hip joint and down the lower limb. It is the longest and widest single nerve in the human body, going from the top of the leg to the foot on the posterior aspect. The sciatic nerve has no cutaneous branches for the thigh. This nerve provides the connection to the nervous system for the skin of the lateral leg and the whole foot, the muscles of the back of the thigh, and those of the leg and foot. It is derived from spinal nerves L4 to S3. It contains fibers from both the anterior and posterior divisions of the lumbosacral plexus. Structure In humans, the sciatic nerve is formed from the L4 to S3 segments of the sacral plexus, a collection of nerve fibres that emerge from the sacral part of the spinal cord. The lumbosacral trunk from the L4 and L5 roots descends between the sacral promontory and al

An integrated interface for peripheral neural system recording and stimulation: system design, electrical tests and in-vivo results

Roberto Puddu, Stanisa Raspopovic

The prototype of an electronic bi-directional interface between the Peripheral Nervous System (PNS) and a neuro-controlled hand prosthesis is presented. The system is composed of 2 integrated circuits: a standard CMOS device for neural recording and a HVCMOS device for neural stimulation. The integrated circuits have been realized in 2 different 0.35 mu m CMOS processes available from ams. The complete system incorporates 8 channels each including the analog front-end, the A/D conversion, based on a sigma delta architecture and a programmable stimulation module implemented as a 5-bit current DAC; two voltage boosters supply the output stimulation stage with a programmable voltage scalable up to 17V. Successful in-vivo experiments with rats having a TIME electrode implanted in the sciatic nerve were carried out, showing the capability of recording neural signals in the tens of microvolts, with a global noise of 7 mu V-rms, and to selectively elicit the tibial and plantar muscles using different active sites of the electrode.

Springer Verlag2016

Framework for the Development of Neuroprostheses: From Basic Understanding by Sciatic and Median Nerves Models to Bionic Legs and Hands

Francesco Maria Petrini, Stanisa Raspopovic, Giacomo Valle, Marek Zelechowski

Neuroprostheses based on electrical stimulation are becoming a therapeutic reality, dramatically improving the life of disabled people. They are based on neural interfaces that are designed to create an intimate contact with neural cells. These devices speak the language of electron currents, while the human nervous system uses ionic currents to communicate. A deep understanding of the complex interplay between these currents, during the electrical stimulation, is essential for the development of optimized neuroprostheses. Neural electrodes can have different geometries, placement within the nervous system, and the stimulation protocols (paradigms of use). This high-dimensional problem is not tractable by an empiric, brute-force approach and should be tackled by exact computational models, making use of our accumulated knowledge. In pursuit of this goal, a hybrid finite element method-NEURON modeling-is used for a solution of electrical field generated by stimulation, within the different neural structures having anisotropic conductivity, and a corresponding neural response computation. In this work, an important correction of perineurium electrical conductivity is computed. Models of median and sciatic nerves, innervating the hand and foot areas, relevant to the development of bionic hands and legs with sensory feedback, are implemented. The obtained results have the potential to optimize the design of neural interfaces, in terms of shape and number of stimulating contacts. Guidelines for the neurosurgical planning are proposed, by indicating the optimal number of implants for a specific nerve to obtain the best efficacy with the lowest invasiveness. The interpretation is proposed for one of the basic problems of neural interfaces, consisting in the change of the stimulation threshold due to fibrotic reaction of tissue. We show that it is possible to use human microstimulation as an experimental setup for testing of afferent stimulation paradigms, which can be translated to further chronic implants. In the future, models will have a key role in the decision of the most appropriate design of customized neuroprostheses, their optimal modality of use, understanding the effects that occur during their use, and minimizing animal and human experimentation.

Ieee-Inst Electrical Electronics Engineers Inc2017

Hybrid peripheral-spinal neuroprosthesis for refined motor execution after paralysis

Sophie Marie Marthe Wurth

Spinal cord injury (SCI) disrupts the communication between the brain and the spinal circuits responsible for movement, thereby causing severe motor deficits. Current strategies to restore function to paralyzed limbs have separately investigated electrical stimulation of the spinal cord or of the peripheral neuromuscular system. Various neuromodulation strategies, for instance electrical epidural stimulation (EES) of the spinal cord, reactivate spinal circuits below the lesion and enable the generation of locomotor activity. EES targets muscle synergies rather than specific muscles or joints, and can therefore be limited by low selectivity. Accessing distal muscles individually is key to restore refined movement. Peripheral nerve stimulation (PNS) offers this possibility by selectively recruiting fibers innervating distinct muscles. Here, I developed a hybrid electrical stimulation paradigm, concomitantly targeting the spinal cord and the peripheral nerves for a global activation of coordinated multi-joint leg movements and a selective activation of distal muscles respectively. This approach combines two highly complementary stimulation paradigms into one refined neuroprosthetic system that could improve functional restoration after paralysis. The first part of this work addressed the validation of intraneural electrodes for selective and stable PNS. Albeit highly promising, incomplete characterization of long-term usability and biocompatibility has so far restricted their widespread use. To bridge this gap, I conducted a longitudinal assessment and comprehensively characterized their functional properties in light of their bio-integration in rats. Results showed that i) stimulation thresholds increased moderately during one month after implantation and then stabilized, ii) these changes correlated with progressive implant encapsulation, and iii) selectivity in muscle recruitment was retained in spite of the encapsulation, permitting precise control over ankle kinematics in anesthetized experiments. Overall, these results demonstrated the potential for long-term usability of intraneural implants. In the second part of this work, I developed and characterized a hybrid PNS-EES paradigm that concomitantly stimulated the spinal cord and the sciatic nerves in rat models of severe SCI, and validated it in a pilot study with a human SCI. I showed that i) muscle recruitment obtained by EES and PNS was highly complementary, ii) PNS enabled controllable adjustments in leg movements during locomotion, and iii) the hybrid PNS-EES paradigm permitted refined movements that increased functionality during locomotion in rats and a human pilot subject. This thesis provides evidence about the long-term functionality of intraneural implants and demonstrates their potential for stable interfacing with peripheral nerves. The hybrid PNS-EES paradigm reveals how the complementarity of both strategies effectively improved functional outcomes for paralyzed lower limbs. These findings open promising perspectives for the development of hybrid neuroprosthetic systems to restore functional and refined movements to paralyzed limbs.

EPFL2018