Median and radial sensory latencies to digit I as compared with other screening tests in carpal tunnel syndrome.
Fifty two patients with suspected carpal tunnel syndrome were evaluated electrodiagnostically by using a variety of screening tests. The criteria of normalcy were as follows: distal median motor latency lower than 4.2 ms, distal median sensory latency wrist-to-third finger at 14 cm higher than 3.2 ms for the onset and than 3.8 ms to the peak, median sensory conduction velocity wrist-to-palm at 7 cm higher than 40 m/s peak-to-peak and difference between median and radial sensory latencies wrist-to-first digit at 11 cm using an intermediate position as site of stimulation and measured peak-to-peak ("bactrian sign") higher than 0.4 ms. Other tests such as median-ulnar comparison using finger 4 were considered less reliable based primarily on the frequent association of carpal tunnel syndrome and Guyon canal entrapment. Carpal tunnel syndrome was confirmed in 49 of 52 suspected cases (94.2%) by at least one abnormal screening test. Bilateral involvement was noted in 65.3% of the cases (32 patients). The "bactrian" (two-hump camels) sign was the single most sensitive test used, being positive in 83.7% of cases. The second most sensitive test was median SNAP (wrist-to-finger) latency and the third, sensory conduction velocity across the carpal tunnel.
Cassvan
A
A
Rehabilitation Medicine and Electrodiagnostic Center, Franklin General Hospital, Valley Stream, New York 11580.
Ralescu
S
S
Shapiro
E
E
Moshkovski
F G
FG
Weiss
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D004568:Electrodiagnosis / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D009431:Neural Conduction; D011826:Radial Nerve / Q000503:physiopathology*; D011930:Reaction Time