The Usefulness of Calculated Electrophysiological Parameters in Assessing the Severity of Carpal Tunnel Syndrome

Background: Carpal tunnel syndrome (CTS) is the most common type of mononeuropathy. Although CTS patients usually have sensory and motor latency in the EMG-NCV or EDX, a significant percentage (10-25%) of patients have a normal routine study. And if more complete diagnostic tests are not performed, it will not be diagnosed. We decided to identify this group of patients by calculating other methods. Methods: We evaluated 131 patients with CTS and 34 persons from the asymptomatic group as controls (297 hands in total). Individuals were then divided into 4 groups: asymptomatic, mild, moderate, and severe based on the severity of the disease. Calculated electrophysiological parameters were measured using nerve conduction studies. For each group, we calculated the sensitivity and specificity of 4 indicators separately including terminal latency index (TLI), residual latency (RL), modified F-wave latency ratio (MFR), difference of the minimal F-wave latencies between the median and ulnar nerves (F-diff M-U), and finally obtained the best parameter according to the total sensitivity and specificity. We also determined the cutting point for each parameter. Results: RL index (90.7%) has the highest sensitivity for diagnosing mild cases and F-diff M-U index (50%) has the highest specificity. TLI and MFR indices have the highest sensitivity for diagnosing moderate cases and RL index (84.6%) has the highest specificity. RL index (94.6%) has the highest sensitivity for diagnosing severe cases and MFR index (86.5%) has the highest specificity. Conclusion: The best indicator for distinguishing CTS from normal cases, as well as determining its severity, is RI.