Clarifying distal axonal properties of the median nerve.
Although length-dependent axonal excitability changes have been reported in the median nerve, the mechanisms underlying these changes remain to be further clarified.
Axonal excitability studies were performed on median nerve at the palm and wrist in 20 healthy controls, with responses recorded over the abductor pollicis brevis.
The strength-duration time constant was significantly shorter (palm: 0.35 ± 0.01 ms; wrist: 0.48 ± 0.03 ms; P < 0.001), whereas rheobase was significantly increased (palm: 2.90 ± 1.12 mA; wrist: 2.09 ± 1.11 mA; P < 0.05) at the palm. In addition, there was a significant increase in depolarizing threshold electrotonus at 90-100 ms (P < 0.001) and a reduction in S2 accommodation (P < 0.001) and late subexcitability (P < 0.001) at the palm. The changes in excitability were independent of factors influencing median nerve cross-sectional area.
The present study reveals significant length dependent changes in median nerve excitability which may reflect differences in intrinsic membrane properties.
Sydney Medical School Westmead, University of Sydney, Sydney, New South Wales, Australia.
SourceMuscle & nerve 45:4 2012 Apr pg 492-9
Pub Type(s)Journal Article