A magnetic evaluation of peripheral nerve regeneration: II. The signal amplitude in the distal segment in relation to functional recovery

Nerve compound action current (NCAC) measurements and morphometric analysis in the proximal segment after nerve transection and repair in a rabbit model

“…Conduction velocity and onset latency did not elicit statistically significant changes, but the conduction velocity demonstrated a trend toward a decrease (101.2 m/sec vs 85.1 m/sec), and onset latency showed a consequent trend toward an increase (0.50 msec vs 0.59 msec) after injury. These MNG results are consistent with previous studies, all of which, using the same experimental model, show this decrease in compound action current amplitude of approximately 60% in the proximal stump at 12 weeks post-reconstruction (Kuypers et al, 1993;1998a;1998b;1995). Other authors, using similar ENG experiments, found that compound action potential amplitudes did not reach control values over 150 days after resuturing the nerve, but remained at 50% to 60% of the control.…”

“…Later experiments showed that conduction velocity decreases in the first weeks after injury, which is consistent with early amplitude decreases. After longer regeneration periods, conduction velocities are reported to return to normal (Kuypers et al, 1998a;1998b;1995) or remain slightly lowered (Cragg and Thomas, 1961).…”

“…Changes in conduction velocity (CV) were also present during the first 8 post-operative weeks, but returned to normal after 12 weeks. This led to the conclusion that the 60% decrease in peak-peak amplitude involved a decrease of approximately 50% in number of functional fibres (Kuypers et al, 1993;1998a;1998b;1995;1999). Supporting this idea, a decrease of 40% to 50% in compound action potential, as opposed to current, was described in separate studies using ENG (Davis et al, 1978).…”

“…It is based on the recording of intra-axonal currents producing nerve compound action currents by means of induction in 2 magnetic sensor coils (toroids). This technique was developed by Wikswo and co-workers Wikswo, 1982;Wikswo and Roth, 1988;Wikswo and van Egeraat, 1991), and adapted by Kuypers and van Egeraat (Kuypers et al, 1993;1998a;1998b;1995;1999) for use in an animal experimental model of regeneration using the common peroneal nerve in rabbits. The main advantage of MNG over more conventional electroneurography (ENG) is the addition of a calibration signal with each measurement, which enables more accurate quantification.…”

“…MNG has been evaluated in healthy frog sciatic nerve (Wijesinghe et al, 1991a;1991b;Wijesinghe and Wikswo, 1991). Furthermore it has been correlated with functional recovery (Kuypers et al, 1999) and with histological and morphometric data after nerve transection and reconstruction in a rabbit model (Kuypers et al, 1998a;1998b). When evaluating nerve regeneration after transection and microsurgical reconstruction of the common peroneal in rabbits using MNG, peak-peak amplitude in the stump proximal to the lesion was consistently 50% to 60% less than it was in the the healthy contralateral control nerve.…”