Peripheral Nerve Magnetoneurography with Optically Pumped Magnetometers

Abstract

The pain experience is a complex process that involves the activation of multiple neuronal signaling pathways that originate in the peripheral nervous system and are transmitted to the central nervous system. In the peripheral nervous system, specialized peripheral nociceptor (unmyelinated C fibers and lightly myelinated A-Delta; fibers) depolarization results in afferent transmission of noxious signals. Small Fiber Neuropathy (SFN) can result in chronic neuropathic pain with significant lifetime morbidity if not promptly treated. Current technological and operator limitations may delay SFN diagnosis and prolong appropriate treatment. Therefore, there is an unmet need for robust and non-invasive ways to accurately measure small fiber function. It is well known that the propagation of action potentials along a nerve is the result of ionic current flow which, according to the Ampere Law, generates a small magnetic field that is detectable by magnetometers such as superconducting quantum interference device (SQUID) Magnetoencephalography (MEG) systems. Optically pumped magnetometers (OPM) are an emerging class of quantum magnetic sensors with a demonstrated sensitivity of 1 fT/SQRT;Hz level, capable of cortical action potential detection. However, they have not as of yet been implemented for peripheral nerve action potential detection. We demonstrate for the first time, compelling evidence that OPM can detect the magnetic signature of travelling peripheral nerve action potentials that indicate OPM use as a potential technique for SFN diagnosis.

Alignment of magnetic sensing and clinical magnetomyography

“…The new generation of MMG sensors, such as TMR, do not have a limitation for frequency bandwidth 12 . However, there is trade-off between the bandwidth and the sensitivity of a magnetic sensor, which means that they cannot be simultaneously, as increasing the bandwidth would reduce the sensitivity of the sensor (Bu et al, 2022).…”