[The value of sensory latency measured on the four median innervated fingers for the diagnosis of the carpal tunnel syndrome].
OBJECTIVE
A prolonged sensory latency (SL) from the wrist to digits innervated by the median nerve is one of the diagnostic criteria of the carpal tunnel syndrome (CTS). Typically, the median SL is measured on the index (D2) or middle finger (D3), but recent studies have shown that the evaluation of SL on the thumb (D1) or the ring finger (D4) may be more sensitive. The aim of this study was to compare the relative sensitivity of the measurements of SL on the four median innervated digits in patients, who were divided into two groups, one of mild and the other of moderate and severe CTS.


METHODS
We examined 253 hands of 172 patients with CTS diagnosis confirmed by electrophysiological studies, including comparative tests. In each case, we tested antidromic onset of SL to digits D1, D2, D3 and D4, and the distal motor latency from the wrist to the abductor pollicis brevis (DML-APB). The control group consisted of 60 healthy subjects.


RESULTS
Antidromic SL to D1 in 83 hands with mild CTS was more frequently abnormal (72%) than SL to D2 (39%), D3 (66%) or D4 (68%) (p < 0.05). In 170 hands with moderate and severe CTS, antidromic SL to D1 was also the most sensitive (96%) test, but the differences between SL to D1 (97%), to D2 (89%), to D3 (94%) and to D4 (96%) were statistically insignificant.


CONCLUSIONS
In conclusion, we can state that SL to D1 is the most sensitive test for the diagnosis of CTS, especially in patients with mild CTS. If we evaluate sensory latency between the wrist and digit 1, the most beneficial solution is to test also digit 3 or 4.
Banach
Marta
M
Klinika Neurologii, Collegium Medicum, Uniwersytet Jagielloński, ul. Botaniczna 3, 31-503 Kraków.
Szczudlik
Andrzej
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002349:Carpal Tunnel Syndrome / Q000503:physiopathology*; D005260:Female; D005385:Fingers / Q000294:innervation* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation