Role of Diffusion Tensor Imaging of the Median Nerve in Carpal Tunnel Syndrome: A Case Control Comparative Study with Electrophysiological Tests and Clinical Assessment

Abstract

Background: Carpal Tunnel Syndrome (CTS) is the most common peripheral neuropathy of an upper extremity. The diagnosis of CTS is commonly based on findings from the medical history, physical examination, and provocative tests. To confirm the diagnosis, some clinician accepts Electrophysiological Studies (EPS) as the reference standard. Diffusion-Tensor Imaging (DTI) is a subtype of diffusion-weighted imaging based on measurement of molecular diffusion along multiple directions in space. Directional anisotropy of water diffusibility can be quantified by imaging indices such as Apparent Diffusion Coefficient (ADC) and Fractional Anisotropy (FA) used to characterize the degree of diffusion anisotropy. Aim of Work: The aim of this study is to study the efficacy of diffusion tensor imaging in the diagnosis of carpal tunnel syndrome. Material and Methods: Twenty-three wrists of 15 healthy subjects and 47 wrists of 31 CTS patients were evaluated with DTI and EPS. FA and ADC of the median nerve were calculated at four locations: Distal radioulnar joint, pisiform bone, hamate bone and hamate hook, and also determined from the whole median nerve. Electrophysiological test, including nerve conduction velocity was also performed for comparison with clinical assessment as a standard of reference. Results: There was a significant difference between healthy individuals and patients with carpal tunnel syndrome (p<0.01 for both FA and ADC). FA value less than 0.54 and ADC value more than 1.19 X 1 0-3 mm 2 /sec might be used in the diagnosis of carpal tunnel syndrome. As regards the DTI results, the sensitivity, specificity, negative predictive value, positive predictive value and accuracy were 97.8%, 95.6%, 95.6%, 97.8% and 97.1% respectively. Conclusion: DTI scan contribute to carpal tunnel syndrome diagnosis on the basis of FA and ADC measurements.