Median to Ulnar Nerve Comparative Conduction Studies on Diagnosis of Carpal Tunnel Syndrome in Early Grades

ABS TRACT Objective: To analyze the utility of various comparative median (MN) to ulnar nerve (UN) conduction study (NCS) techniques in detecting carpal tunnel syndrome (CTS). Material and Methods: We retrospectively analyzed our NCS recordings that belong to the patients who were consecutively referred to our laboratory within a year. The best cut off points and diagnostic efficiencies of the parameters based on comparison of MN and UN distal sensory onset latencies (DSOLs) and peak latencies (DSPLs) over fourth finger and second-to-fifth finger, SNAP amplitudes, MN-thenar and UN-hypothenar distal motor latencies (DMLs), minimum F wave latencies (mFWLs), CMAP amplitudes, motor conduction velocities, and MN sensory and UN motor latency (MS-UM) on electrodiagnosis of CTS were detected beside ones of conventional conduction parameters. Results: Totally 109 recordings among the 210 upper extremity recordings were included. CTS was clinically diagnosed in 59 hands (54.1%). MN DSOL and DSPL over fourth finger had the highest diagnostic efficiency values (88.1% and 87.2%, respectively) among conventional parameters, whereas MN to UN DSOL and DSPL differences over fourth finger had the highest ones (93.6% and 90.8%, respectively) among comparative parameters. MN DSOL and DSPL values, over both second and fourth fingers, had good overall agreement in confirming the CTS diagnosis. That was also true for MN to UN DSOL and DSPL differences on fourth finger, but not for ones on second to fifth finger DSOL and DSPL comparisons. The diagnostic efficiency values were 80.7% for DML difference and 78% for mFWL difference. Conclusion: DSOL and DSPL differences over fourth finger have a favorable diagnostic efficiency values on CTS diagnosis. Although the MN to UN DML and mFWL differences are more efficient in CTS diagnosis, their diagnostic efficiency rates are lower than ones of sensory parameters. Future studies are warranted to consider their possible usefulness of them for diagnosing CTS in patients with concomitant polyneuropathy or unelicitable sensory responses because of technical pitfalls during the sensory NCSs.