NONINVASIVE NEUROMAGNETIC MONITORING OF NERVE AND MUSCLE INJURY CURRENTS

Structural damage inflicted on membranes of excitable cells may evoke quasi-DC injury currents driven by the transmembrane resting potential gradient. In contrast to the usually invasive electrophysiological ap proaches, superconducting quantum interference devices (SQUIDs) measur e the concomitant weak biomagnetic fields non-invasively as is shown h ere for acutely excised rat nerves or muscles. Analysis of the field d istributions showed slowly decaying equivalent current dipole moments in the nanoampmeter range as generated by microamp nerve injury curren ts extending intra-axonally over millimeter distances. The geometric a nd kinetic parameters of this experimental design may allow in vivo re cordings in human patients.