Clinical-neurophysiological and quantitative MR imaging assesment in patients with idiopathic carpal tunnel syndrome

Abstract

Objective: To evaluate the significance of magnetic resonance imaging (MRI) in carpal tunnel syndrome (CTS) by evaluating with clinical and electrophysiologic findings. Material and Methods: Twenty one patients diagnosed clinically and electrophysiologically with CTS were included in the study. Median nerve area and “flattening ratio” were evaluated on MRI along with flexor retinaculum thickness at the levels of radioulnar joint (level 1), os psiforme (level 2) and os hamatum (level 3). The findings of MRI were compared with those obtained from the controls at the similar age. The association between clinical and electrophysiologic stages were investigated according to the positivity and negativity of Phalen and Tinel tests, in addition to the correlation between clinical and electrophysiologic stages. The selectivity, sensitivity of MRI, and its positive and negative predictive values in the diagnosis of CTS were also assessed using ROC analysis. Results: While median nerve area at radioulnar joint was significantly wider at os psiforme level, “flattening ratio” of median nerve was significantly greater at all levels (p=0.002, p=0.001 and p=0.001, respectively). The thickness of flexor retinaculum was also significantly greater in CTS cases (p=0.001). Although a moderate correlation was present between clinical and electrophysiologic stages (r=0.664, p=0,001), the averages between Tinel or Phalen tests and clinical and electrophysiologic stages were found to be similar (p=0.880 and p=0.841, respectively). In clinical evaluation, however, when the findings of MRI positivity were assessed in positive predictive values indicating CTS possibility, median nerve area and flattening ratio were found to be the greatest at levels 2 and 3 (82.4% and 92.9%), and thickness of flexor retinaculum was determined as 85.7%. Conclusion: The diagnostic validity of MRI is not high enough to be used alone in the diagnosis of CTS. However, it can be used to find the reason of CTS, especially for determination of lesions in carpal tunnel or anatomic variations in the cases where conservative treatments are failed or insufficient.