Diagnosis of C8 radiculopathy by magnetospinogram

Abstract

It is difficult to detect lesion proximal to Erb’s point in peripheral nerve by conventional electroneurophysiological study. Here, we report two cases of C8 radiculopathy diagnosed by our prototype magnetospinogram (MSG) system with highly sensitive SQUID sensors. Case 1: A 57 year-old-male presented with weakness and sensory disturbance in the right upper limb for 5 months. Case 2: A 56 year-old-male presented with weakness and sensory disturbance in the left upper limb for 2 and half years. In both cases, neurological findings, nerve conduction test and needle electromyogram findings suggested a disturbance between the proximal part to C8 dorsal root ganglion and the spinal cord. The neuromagnetic fields were measured from the brachial plexus and cervical cord in response to electrical supramaximal stimulation of the ulnar nerve at the elbow by using a newly developed 132-channel MSG system. The action currents were reconstructed from the evoked magnetic field by a spatial filter, recursive null steering beamformer and superimposed on the X-ray image. Virtual electrodes were set along nerve travel and equivalent current waveforms at each site were determined and compared. [Results] In both cases no conduction failure was pointed out in the affected side brachial plexus and the estimated electrical currents in the affected side C8 intervertebral foramen were smaller than that on the non-affected side. Because MSG can evaluate nerve activity sequentially with high spatial resolution, we believe it will be useful in clinical diagnosis.