Role of High Resolution Ultrasound in Assessment of Abnormalities of Median Nerve in Carpal Tunnel Syndrome

Background: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and consists of the compression of the median nerve as it courses through the carpal tunnel. Carpal tunnel syndrome was diagnosed by history and physical examination, electrodiagnostic studies (EDX) were used to confirm the diagnosis. However, these studies are painful for most of the patients with high incidence of false positive or false negative results. Ultrasound is a low cost, short time and non-invasiveness technique that could be used to assess a number of parameters of the median nerve (MN) in cases of CTS. Objective: To assess the utility of high resolution ultrasound (HRUS) in assessment of median nerve in carpal tunnel syndrome through different ultrasound diagnostic criteria in patients with clinical and electrodiagnostic evidence of CTS. Patients and Methods: This study included a total of 60 participants divided into 2 groups; group A, the patients group included 30 patients with a clinical diagnosis of carpal tunnel syndrome (CTS) and group B, the control group who included 30 sex and age-matched healthy individuals. All the included cases were subjected to full history taking, full general and general examination. Nerve conduction studies were performed using a Caldwell Sierra Wave and the NCS consisted of sensory median nerve conduction tests using standard techniques. High resolution US was performed by using an Aplio 400 Ultrasound System. The following measurement was recorded in each of the included subjects including cross sectional area (CSA) of the median nerve, flattening ratio (FR) of median nerve and palmar bowing (PB) of the flexor retinaculum. Results: There was high statistically significant difference in the mean CSA and mean PB between the cases with CTS and healthy control. No statistically significant difference in the mean FR between the cases with CTS and healthy control. Optimal CSA cut-off value to differentiate between cases with CTS and control was (10.2 mm2) and the optimal PB cut-off value to differentiate between cases with CTS and control was (3.3 mm). Positive correlation was detected between the CSA and PB with increasing the severity of CTS. Conclusion: Electrophysiological studies are the most utilized diagnostic methods for diagnosing nerve entrapment including median nerve in CTS. Hugh resolution ultrasound (HRUS) is non- invasive sensitive diagnostic tool in diagnosing CTS.