Evaluation of Ultrasound in Diagnosis of Carpal Tunnel Syndrome: A Hospital Based Cross Sectional Study

Abstract

Background: Nerve conduction study is considered as the gold standard for diagnosis of carpal tunnel syndrome (CTS). Ultrasonography provides a simple non-invasive means of visualizing peripheral nerve pathology. Objective: The objective of the study was to assess the role of ultrasonography in CTS and its correlation with the present-day gold standard of nerve conduction studies (NCS). Materials and Methods: A prospective cohort size of 50 subjects was calculated based on a hypothesized sensitivity of 85%. All 50 patients underwent nerve conduction studies and USG. Transverse images of the median nerve were obtained at two levels: proximal to the carpal tunnel inlet, at the carpal tunnel inlet. Statistical analysis was done to correlate the ultrasound findings at each level with nerve conduction studies and calculation of the positive and negative predictive values. The cut offs of the cross-sectional areas of the median nerve at the two anatomical levels on ultrasonography were taken at the best sensitivity and specificity. Results: We found that at any one anatomical level, the sensitivity of ultrasound to detect carpal tunnel syndrome by increase in the cross-sectional area of median nerve as compared to the nerve conduction studies is 85%. Conclusions: At 84% specificity, ultrasonography could be used as a non-invasive and easily available screening tool in carpal tunnel syndrome. Also, the best level to look for nerve compression is at the level of the carpal tunnel inlet.