Correlation of median forearm conduction velocity with carpal tunnel syndrome severity.
OBJECTIVE
Median nerve entrapment neuropathy at the wrist can be accompanied by slowed motor conduction within the forearm. Existing studies conflict regarding a correlation between the severity of the entrapment neuropathy in carpal tunnel syndrome (CTS) and slowing of median motor nerve conduction velocity (MNCV) in the forearm. Here, it was asked if there is a correlation between markers of CTS severity and median forearm MNCV, and if there is an explanation for the preceding conflicting results.


METHODS
Median MNCV in the forearm was correlated with neurophysiologic markers of severity of a median neuropathy at the wrist in 91 hands from 64 patients with clinical and electrodiagnostic evidence of CTS.


RESULTS
Median MNCV within the forearm segment was negatively correlated with the median nerve distal motor latency (r=-0.64, P<0.001, n=91) and positively correlated with the CMAP amplitude of the abductor pollicis brevis muscle (r=0.45, P<0.001, n=91). These correlations only occurred in patients with a prolonged median distal motor latency. Previous investigations that failed to find such correlations used variable or non-standardized methods or analyzed smaller numbers of patients.


CONCLUSIONS
Slowing of median MNCV in the forearm is related to the severity of the entrapment of median motor fibers at the wrist.


CONCLUSIONS
Slowed forearm median MNCV can be a marker of motor nerve injury at the wrist.
Havton
Leif A
LA
Department of Neurology and Brain Research Institute, David Geffen School of Medicine at UCLA, University of California-Los Angeles, 710 Westwood Plaza, Los Angeles, CA 90095-1769, USA. lhavton@mednet.ucla.edu
Hotson
John R
JR
Kellerth
Jan-Olof
JO
D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002349:Carpal Tunnel Syndrome / Q000473:pathology / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D005260:Female; D005542:Forearm / Q000294:innervation*; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology* / Q000528:radiation effects; D013223:Statistics as Topic