Usefulness of the median terminal latency ratio in the diagnosis of carpal tunnel syndrome.
OBJECTIVE
The sensitivity of the median terminal latency (MTL) ratio was compared to that of standard conduction techniques for diagnosing carpal tunnel syndrome (CTS).


METHODS
We analyzed 153 patients (274 hands) with clinically suspected CTS and 100 volunteers. Median motor conduction velocity and sensory nerve conduction velocity (MCV and SCV, respectively) were evaluated using traditional methods. The wrist-palm (W-P) MCV and two motor distal latency differences (LDs) between the median and ulnar nerves were measured. The MTL ratio was calculated by dividing the MTL-W by MTL-P. The ratio of distal to proximal conduction (disto-proximal ratio) was calculated.


RESULTS
The sensitivity of the motor nerve conducting technique was 77.7% in the W-P MCV, 72.6% in the median thenar-ulnar thenar LD, 63.9% in the median thenar-ulnar hypothenar LD, 59.9% in the MTL-P, 60.2% in the MTL-W, and 81.8% in the MTL ratio. The sensitivity of the median sensory nerve conduction method was 89.1% in the W-second F segment, 89.1% in the W-third F segment, 90.5% in the W-P segment, and 92.3% in the disto-proximal ratio of the third finger.


CONCLUSIONS
The disto-proximal ratio in the third finger was the most sensitive. Among the motor conduction studies, the MTL ratio was the most sensitive.


CONCLUSIONS
These ratios can facilitate accurate diagnosis of patients with CTS.
Lee
Kyu-Yong
KY
Department of Neurology, College of Medicine, Hanyang University, 249-1 Guri Hospital, Gyomun-dong, Guri-si, 417-710 Gyeonggi-do, Republic of Korea.
Lee
Young-Joo
YJ
Koh
Seong-Ho
SH
D000328:Adult; D000368:Aged; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis* / Q000503:physiopathology*; D016022:Case-Control Studies; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012680:Sensitivity and Specificity; D014459:Ulnar Nerve / Q000503:physiopathology