Visualization of incomplete conduction block by neuromagnetic recording

Objective: We previously reported on evoked compound action magnetic fields (CAFs) in isolated sciatic nerves with complete conduction block. In this study, we examined evoked CAFs of the nerve with incomplete conduction block, which is clinically common. Methods: Rabbitsʹ isolated nerves were electrically stimulated in a chamber containing Ringerʹs solution. Compound action potentials (CAPs) and CAFs were recorded before and after the incomplete conduction block induced by a vascular clip. The positions of the lesion were estimated by dipole localization. Results: Before the nerve clipping, magnetic contour maps showed CAFs with a characteristic quadrupolar pattern. After the clipping, CAFs attenuated in the amplitude and decelerated through the lesion. Estimated position of the lesion was 0.12±3.23 mm (mean±SD, n=10) assuming that the real position of the clip was 0 mm. Conclusions: The time-course of changes of CAFs in the incomplete conduction block was visualized by magnetic contour maps, and the lesions were closely localized focusing on the velocity change of the leading dipole. Significance: The neural conduction with incomplete conduction block was visualized and the lesion was closely localized by neuromagnetic recordings.