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. Author manuscript; available in PMC: 2013 Jun 7.
Published in final edited form as: J Neurosci. 2010 Jan 13;30(2):600–608. doi: 10.1523/JNEUROSCI.4264-09.2010

Figure 1. Experimental paradigm for nerve compression, and mechanically induced CB in mice.

Figure 1

A. This diagram shows the placement of stimulation (arrows) and recording (marked by R) electrodes for NCS. B. Compression was delivered by a nylon cord loop attached a 400g weight. This diagram shows the cross-section at the site of nylon cord. The leg rests on a metal plate (marked as ‘bridge’) with a width of about 1 cm. Tibial nerves usually run on the medial side of the ankle (red dot). C. In the second set of experiments, the angle between the nylon cord and the vertical line of leg is reduced by 15 degrees by shortening the length of the bridge (arrow in C). D. An example of NCS from a compression experiment on a wild-type mouse is shown. In the D-left figure, similar amplitudes of CMAP were evoked by stimulations at the distal and proximal sites. After compression was applied, CMAP amplitude from the proximal stimulation was reduced >60% of the CMAP amplitude by the distal stimulation, called CB (D-middle figure). At this point, compression was removed. At the day 5 after the compression, CB recovered (D-right figure). E. The same experiment was performed on a pmp22+/− mouse. CB did not recover at day 5 following compression (E-right figure). Sensitivity = 1mV; Speed = 1ms. Notice that the onset of CMAP in mice may be obscured by an evolving positive-deflection. Thus, peaks of CMAP were often used to calculate the latency and conduction velocity. Nevertheless, this issue does not affect the measurement of CMAP amplitudes or any of our conclusions. F. An original trace recorded at the hypothenar muscle of a patient with HNPP: Stimulations on the ulnar nerve inched 1 cm/step across the elbow, a location subject to compression. A focal slowing (a long delay from trace 2 to 3 in contrast to a very short delay from 1 to 2 or from 3 to 4) across the elbow was identified within a 1cm segment of the nerve, demonstrating the very focal nature of the slowing. CB was conspicuous in this case. Arrow indicated the third response which had a >50% amplitude drop of motor response, and was associated with weakness in muscles innervated by the ulnar nerve. G. Induction time for CB was compared between wild-type and pmp22+/− mice in the second set of experiments (see 1C) and was significantly shorter in pmp22+/− mice (p<0.01; error bars = standard deviation).