Intraneural Vascular Resistive Index of the Median Nerve as a Predictor of Severity of Carpal Tunnel Syndrome

Objective: There is a limited data about resistive index (RI) of median nerve (MN) in patients with carpal tunnel syndrome (CTS). In our study, we aimed to evaluate the relationship between CTS severity and MN-RI. Methods: A total of 115 CTS patient wrists, and 49 wrists of control subjects without CTS, were examined on ultrasonography (US) and color Doppler US (CDUS), pulsed Doppler ultrasonography (PDUS), and by electrophysiological evaluations. MN peak-systolic velocity (MN-PSV), MN end-diastolic velocity, MN-RI and MN pulsatility index (MN-PI) were measured by PDUS. Patients were divided into 3 groups according to electrophysiological examinations severity findings of CTS as mild (Group-I), moderate (Group-II), and severe (Group-III). Results: MN-PSV, MN-PI and MN-RI increased significantly from Group-I to Group-III and these parameters were significantly higher in Group-III than other two groups. MN-RI independently determines the patients to have severe CTS. Increased MN-RI (per-0.1) was found to increase the risk of having severe CTS by 3.45-times. In the ROC analysis, the area under the curve was 0.846 for MN-RI. When the MN-RI cut-off value was taken as 0.80, it determines patients to be severe CTS with 85.2% sensitivity and 78.2% specificity. Conclusion: The increase in MN-RI in CTS patients is independently associated with disease severity and may be used in the clinical follow-up of these patients. Keywords: Carpal tunnel syndrome, median nerve, pulsed doppler ultrasounography, resistive index