Electrophysiologic mapping and cadaveric dissection of the lateral foot: implications for tibial motor nerve conduction studies.
OBJECTIVE
To clarify, through electrophysiologic mapping and cadaveric dissection of the lateral foot, the previously published "proximal" and "distal" recording sites for tibial motor nerve conduction studies.


METHODS
Observational.


METHODS
Electromyography laboratory; anatomy laboratory.


METHODS
Ten asymptomatic feet; eight cadaveric feet.


METHODS
(1) Amplitudes and onset latencies of compound muscle action potentials (CMAPs) recorded over a grid on the lateral foot that included the "proximal" and "distal" recording sites; (2) nerve supply and anatomic boundaries of the abductor digiti minimi pedis (ADMP) and nearby muscles, particularly as they relate to the above recording sites.


RESULTS
(1) Relatively large CMAPs were recorded at and around the "proximal" and "distal" sites, with significantly shorter "proximal" latencies. (2) In all cadaveric feet, ADMP was innervated by only the inferior calcaneal nerve (ICN) and was located deep to the "proximal" site, with virtually no muscle fibers deep to the "distal" site. The flexor digiti minimi brevis (FDMB) was conspicuously located immediately deep to the "distal" site and was innervated by only the lateral plantar nerve (LPN).


CONCLUSIONS
This study strongly suggests that the "proximal" site records predominantly from the ICN-innervated ADMP, whereas the "distal" site predominantly records from the LPN-innervated FDMB.
Department of Physical Medicine and Rehabilitation, Medical College of Wisconsin, Milwaukee 53226, USA.
D R
DR
Del Toro
A
A
Mazur
W W
WW
Dwzierzynski
T A
TA
Park
D000328:Adult; D005260:Female; D005528:Foot / Q000294:innervation*; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D013979:Tibial Nerve / Q000033:anatomy & histology / Q000502:physiology*