Segmental analysis of motor conduction velocity in distal tracts of tibial nerve: a coaxial needle electrode study.
OBJECTIVE
To describe a new method of segmental analysis of motor nerve conduction velocity (mCV) in the tibial nerve (Tn) tract distal to the upper margin of the tarsal tunnel (TT).


METHODS
Compound muscle action potentials (CMAPs) were recorded with a coaxial needle electrode from the flexor hallucis brevis muscle (FHB), to test the medial plantar nerve (MPn), and from the flexor digiti quinti brevis (FDQB) and the first dorsal interosseous (FDI) muscles, to test the superficial and deep branches of the lateral plantar nerve (sLPn and dLPn, respectively). CMAPs were elicited by stimulating at three sites located above (S1) and below (S2) the TT and at the sole of the foot (S3 for MPn and S4 for LPn).


RESULTS
In 20 normal subjects the mean mCV in the proximal (S1 to S2) tract was 44.5+/-4.7, 43.5+/-5.9 and 42.6+/-4.2m/s for the MPn, sLPn and dLPn, respectively. The corresponding values in the intermediate tract (S1 to S3/S4) were 40.7+/-5.6, 39.4+/-5.6 and 40.9+/-5.8m/s.


CONCLUSIONS
Segmental analysis of mCV in distal Tn can be performed when CMAPs are recorded using a coaxial needle electrode, which prevents simultaneous recording of activity from nearby muscles groups.


CONCLUSIONS
Conventional neurophysiological examination for suspected entrapments in distal Tn usually can not discriminate between a lesion inside the TT or distal to it. The proposed technique, as suggested by the reported results in clinical application, may help to better define the lesion site.
Troni
Walter
W
Service of Neurology and Clinical Neurophysiology, Clinica San Luca, Moncalieri, Turin, Italy. javier.rodriguez.falces@gmail.com
Parino
Enrico
E
Pisani
Pier Carlo
PC
Pisani
Giacomo
G
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D000842:Ankle / Q000033:anatomy & histology / Q000502:physiology; D001369:Axons / Q000502:physiology*; D004566:Electrodes; D004568:Electrodiagnosis / Q000379:methods*; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods; D005260:Female; D005528:Foot / Q000294:innervation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation; D009431:Neural Conduction / Q000502:physiology*; D009482:Neurophysiology / Q000379:methods; D011930:Reaction Time; D012016:Reference Values; D013641:Tarsal Tunnel Syndrome / Q000175:diagnosis / Q000503:physiopathology; D013979:Tibial Nerve / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult