Magnetic Field Produced by Compound Action Potential of Degenerated Human Nerve

Abstract

In this study, we discussed about a new diagnostic technique of peripheral nervous disturbance using biomagnetic measurement. The magnetic fleld around a limb after nerve stim- ulation was simulated for the cases when some of the nerve flbers composing the nerve are lacked. As a result, disappearance of a pair of peaks of in- and out-∞ux was observed. The magnetic fleld seems to be re∞ective on the change of the distribution of the number of nerve flbers inside a nerve. 1. INTRODUCTION The nerve conduction velocity test is a general method to diagnose diabetic neuropathy or any other malfunctions of peripheral nerves. Usually in this test, the conduction velocity of skin potential generated by the compound action potential of the nerve is measured. However as the most part of the skin potential is contributed to by thick nerve flbers, degeneration of thin nerve flbers is di-cult to flnd with this test (1). Measurement of magnetic fleld as the substitute of skin potential has an advantage to analyze the property of compound action potential. The action potential of a nerve flber is possible to generate a pair of positive and negative peaks, whose location re∞ects the depth and the thickness of the flber. On the contrary, the magnetic fleld of it has two pairs of peaks of in- and outmagnetic ∞ux (2). As each location re∞ects the depth and the thickness of the flber, the more implications about morphology seemed to be obtained. To investigate the relationship between compound action potential and the magnetic fleld of its produce, the magnetic fleld around a limb after electric current stimulation was simulated. 2. METHODS