MAPPING OF TIBIAL NERVE EVOKED MAGNETIC-FIELDS OVER THE LOWER SPINE

Using a low-noise 49-channel de-SQUID system spinal somatosensory evok ed fields (SEF) were recorded which were generated by compound action currents evoked upon posterior tibial nerve stimulation. The SEF mappi ng showed the action current propagation along the sciatic nerve, lumb osacral plexus and cauda equina in parallel to simultaneously recorded electrical potentials (SEP). For a reliable intraindividual side-to-s ide comparison of spinal SEFs the right and left tibial nerves were st imulated in alternating order; this procedure minimizes artifactual in ter-nerve SEF map differences due to eventual patient-to-sensor displa cements which might occur in serial measurements. These large-area lum bar SEF mappings open up several clinical perspectives for magnetoneur ography, in particular with respect to the 3D-localization of proximal conduction blocks. (C) 1997 Elsevier Science Ireland Ltd.