Electrically Evoked Compound Action Potential Recording in Peripheral Nerves

Abstract

Applications for bioelectric medicine can be found in all parts of the nervous system. The CNS -brain and spinal cord -contain targets for commercial neuromodulation therapies. Peripheral nerves are also modulated with commercially available systems during treatment for chronic pain and epilepsy, and developments are in progress for treating many other diseases. The electrically evoked compound action potential is a measure of the electrical response from the tissue to stimulation. It provides a direct insight into the electrophysiology of the stimulation, and despite its incorporation into cochlear implants it is a technology that is yet to find its way into commercial peripheral nerve stimulation applications. This review outlines the status of evoked compound action potential measurements on peripheral nerves and highlights the challenges which need to be overcome. Recording of the neural activity generated by electrical stimulation forms the basis of a number of diagnostic procedures. It is often performed in an acute setting and the technology has found its way into several active implantable devices. The techniques rely on a stimulus applied to the nerve or tissue to evoke a compound action potential. The stimulus simultaneously and synchronously recruits many fibers and hence the response is referred to as a compound action potential because it is the sum of the many potentials recruited. Summation and synchronous generation increase the amplitude of the response and thus makes detection feasible. Recording the electrical activity of peripheral nerve neurons is common place in a number of diagnostic procedures [1]. Nerve conduction studies are performed to assess the integrity of the nerve and form part of a diagnosis of a range of conditions including Guillain Barre, carpal tunnel syndrome [2], herniated discs, chronic inflammatory polyneuropathies and other nerve disorders including peripheral nerve injury. The direct response from the nerve or the response from a muscle that the nerve innervates is recorded (EMG) in these studies. The nerve conduction velocity is a measure of nerve health -velocities between 50 and 60 ms -1 are considered in the normal range and velocities outside this range could be an indicator of disease. Neural monitoring, measurement of peripherally evoked potentials from the somatosensory cortex, is used to ensure safety during spine surgery [3]. Compound action potential measurement capabilities are built into cochlear implants and are used as objective measures during device setup and programming [4]. Peripheral nerve recordings form the basis of numerous scientific investigations and are used to assess the impact of drugs or to provide baseline calibration of neural activities as part of deeper investigations.Recordings from the nervous system inform clinicians about the health of nerves or their safety during procedures. They inform researchers about mechanisms of action and provide fundamental data for mechanism-based research. Their scope and use is broad but here we will f...

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Anodal block permits directional vagus nerve stimulation

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Ex Vivo Whole Nerve Electrophysiology Setup, Action Potential Recording, and Data Analyses in a Rodent Model

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