The diagnosis of patients with severe carpal tunnel syndrome (CTS) who do not respond to median nerve stimulation and of those with early CTS who report symptoms but show no abnormalities in standard tests is the most challenging. The aim of the study was to assess correlations between the 2LI-DML test and standard tests used for the diagnosis of CTS (SL-D2, DML-APB, D4M-D4U). The study involved 172 patients (253 nerves) with clinical symptoms of CTS. The sensitivity of the 2LI-DML test and standard tests was analyzed in 6 groups of patients classified according to the severity of CTS, assessed by an electrophysiological study. We showed a significant relationship between the results of the 2LI-DML test and those of standard tests (SL-D2, DML-APB, D4M-D4U), as revealed by a topographic analysis of sensory and motor fibers of the median nerve at the site most vulnerable to compression.