Carpal tunnel syndrome: comparison of the median sensory nerve conduction findings from the index and middle fingers.

The sensory nerve conduction study (NCS) is a sensitive means for demonstrating the localized median nerve dysfunction at the wrist in carpal tunnel syndrome (CTS). We reviewed the sensory NCS data of 102 patients (178 median nerves) with CTS and tried to determine if there were significant differences in the findings between the index and middle fingers. There was no statistically significant difference in the amplitudes of the compound sensory nerve action potentials (CSNAPs) recorded antidromically from the index and middle fingers during median nerve stimulation at the palm and wrist. Moreover, there was no statistically significant difference in the finger-to-palm and palm-to-wrist sensory nerve conduction velocities (CVs) between the index and middle fingers. The mean CSNAP amplitudes and mean sensory CVs were comparable in values from these two fingers and they showed a high and positive correlation. It appears that the sensory nerves to the index and middle fingers are compromised to a similar degree in CTS, and neither finger will reveal significantly more sensory conduction abnormalities than the other will.