Evaluation of neural activity by magnetospinography with 3D sensors

Abstract

Objective: Magnetospinography (MSG) has been developed for clinical application and is expected to be a novel neurophysiological examination. Here, we used an MSG system with sensors positioned in three orthogonal directions to record lumbar canal evoked magnetic fields (LCEFs) in response to peripheral nerve stimulation and to evaluate methods for localizing spinal cord lesions.

Methods: LCEFs from the lumbar area of seven rabbits were recorded by the MSG system in response to electrical stimulation of a sciatic nerve. LCEFs and lumbar canal evoked potentials (LCEPs) were measured before and after spinal cord compression induced by a balloon catheter. The lesion positions were estimated using LCEPs and computationally reconstructed currents corresponding to the depolarization site.

Results: LCEFs were recorded in all rabbits and neural activity in the lumbar spinal cord could be visualized in the form of a magnetic contour map and reconstructed current map. The position of the spinal cord lesion could be estimated by the LCEPs and reconstructed currents at the depolarization site.

Conclusions: MSG can visualize neural activity in the spinal cord and localize the lesion site.

Significance: MSG enables noninvasive assessment of neural activity in the spinal canal using currents at depolarization sites reconstructed from LCEFs.

Keywords: Lumbar spinal canal; Magnetoneurography; Magnetospinography; Neuromagnetography; SQUID; Spatial filter; Spinal cord evoked magnetic field; Spinal cord evoked potential.