Fig. 1

Two channels median SSEPs after stimulus of the right median nerve. In a normal SSEP (panel 1), the channels show the cortical responses N20 and P25, the spinal component (N13) and the peripheral component (N9). In the panel 2, N20 and P25 were presented but amplitudes were reduced. In the panel 3, N20 and P25 were absent; A superposed Evoked Potentials; B averaged Evoked Potentials. i-Erb ipsilateral Erb’s point, c-Erb contralateral Erb’s point