 3. To study the correlation between sonographic scores and electrophysiological scores by making a électroneurogramme ENG in the different subjects of subgroups: the amplitude and distal motor latency for distal motor conduction, the motor conduction velocities, the presence of time dispersion or of a conduction block to the stepped motor conduction, the latency of the waveform F to the proximal motor conduction and the amplitude of the sensory potential for sensory conduction. 