Carpal tunnel syndrome assessment with diffusion tensor imaging: Value of fractional anisotropy and apparent diffusion coefficient

Objectives: To quantitatively assess carpal tunnel syndrome (CTS) with DTI by evaluating two approaches to determine cut-off values. Methods: In forty patients with CTS diagnosis confirmed by nerve conduction studies (NCs) and 14 healthy subjects (mean age 58.54 and 57.8 years), cross-sectional area (CSA), apparent diffusion coefficient (ADC) and fractional anisotropy (FA) at single and multiple levels with intraobserver agreement were evaluated. Results: Maximum and mean CSA and FA showed significant differences between healthy subjects and patients (12.85 mm² vs. 28.18 mm², p < 0.001, and 0.613 vs. 0.524, p=0.007, respectively) (10.12 mm² vs. 19.9 mm², p<0.001 and 0.617 vs. 0.54, p=0.003, respectively), but not maximum and mean ADC (p > 0.05). For cut-off values, mean and maximum CSA showed the same sensitivity and specificity (93.3 %). However, mean FA showed better sensitivity than maximum FA (82.6 % vs. 73.9 %), but lower specificity (66.7 % vs. 80 %), and significant correlation for maximum CSA, 97 % (p < 0.01), with good correlation for maximum ADC and FA, 84.5 % (p < 0.01) and 62 % (p=0.056), respectively. Conclusions: CSA and FA showed significant differences between healthy subjects and patients. Single measurement at maximum CSA is suitable for FA determination. Key Points • DTI showed that FA is stronger than ADC for CTS diagnosis. • Single- and multiple-level approaches were compared to determine FA and ADC. • Single-level evaluation at the thickest MN cross-sectional area is sufficient.