Regional differences in ulnar nerve excitability may predispose to the development of entrapment neuropathy.
OBJECTIVE
To assess whether there are differences in nerve excitability properties between proximal and distal stimulation sites in the ulnar nerve in healthy controls, which may provide information on whether alteration in ion channel function predisposes to the development of ulnar neuropathy at the elbow.


METHODS
Nerve excitability studies were undertaken in 11 healthy controls. Studies were undertaken with stimulation of the ulnar nerve at the elbow and wrist. Recordings were obtained from abductor digiti minimi in both sets of studies.


RESULTS
Recordings obtained following stimulation of the nerve at the elbow demonstrated significant differences to those obtained following stimulation of the nerve at the wrist. Specifically, there was a left shift in stimulus-response curves at the elbow compared to the wrist, with prolonged strength-duration time constant, and reduced rheobase (P<0.05). These changes were accompanied by increased refractoriness and reductions in superexcitability and late subexcitability (P<0.05).


CONCLUSIONS
The present findings may suggest relative depolarization of ulnar nerve axons at the elbow.


CONCLUSIONS
These changes may reflect regional differences in axonal Na(+)/K(+) pump function and thereby predispose the ulnar nerve to conduction failure and axonal degeneration when exposed to trauma.
Krishnan
Arun V
AV
Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Australia. arun.krishnan@unsw.edu.au
Park
Susanna B
SB
Payne
Mike
M
Lin
Cindy S-Y
CS
Vucic
Steve
S
Kiernan
Matthew C
MC
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001369:Axons / Q000502:physiology*; D020430:Cubital Tunnel Syndrome / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology; D014459:Ulnar Nerve / Q000503:physiopathology*; D017769:Ulnar Nerve Compression Syndromes / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D055815:Young Adult
D007473:Ion Channels; D000254:Sodium-Potassium-Exchanging ATPase