Role of Conventional MR 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, provocative tests and Electrophysiological Studies (EPS) as the reference standard, but in some cases the results may be equivocal due to discrep-ancies in the different measured clinical parameters. Imaging has the potential to resolve these discrepancies. Fat-saturated, T2-weighted Magnetic Resonance Imaging (MRI) can reveal morphological changes in CTS patients, such as nerve enlarge-ment, nerve flattening, increased nerve signal intensity, and bowing of the flexor retinaculum.
Aim of Work: The aim of this study is to study the role of conventional MRI in the diagnosis of Carpal Tunnel Syn-drome (CTS).
Patients and Methods: Twenty-three wrists in 15 healthy subjects and 47 wrists in 31 CTS patients were evaluated with MRI and Electrophysiological Studies (EPS). The qualitative and quantitative analysis of MRI include: (1) The high signal intensity of the Median Nerve (MN) on the T2W and PD fat suppressed weighted images, (2) Flexor Retinaculum (FR) bowing and measurements of its height and area, (3) Flattening ratio of the MN, (4) MN CSA. EPS; 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 CTS for all qualitative and quantitative MRI interpretation. This includes, the higher SI of the MN on both T2 and PD WIs, the greater FR bowing area and height, the higher flattening ratio of the MN at CT and the greater value of MN CSA. As regards the MRI 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: MRI can contribute to carpal tunnel syndrome diagnosis on the basis of its qualitative and quantitative measurements.