New sonographic measures of peripheral nerves: a tool for the diagnosis of peripheral nerve involvement in leprosy

To evaluate ultrasonographic (US) cross-sectional areas (CSAs) of peripheral nerves, indexes of the differences between CSAs at the same point (ΔCSAs) and between tunnel (T) and pre-tunnel (PT) ulnar CSAs (ΔTPTs) in leprosy patients (LPs) and healthy volunteers (HVs). Seventy-seven LPs and 49 HVs underwent bilateral US at PT and T ulnar points, as well as along the median (M) and common fibular (CF) nerves, to calculate the CSAs, ΔCSAs and ΔTPTs. The CSA values in HVs were lower than those in LPs (p < 0.0001) at the PT (5.67/9.78 mm²) and T (6.50/10.94 mm²) points, as well as at the M (5.85/8.48 mm²) and CF (8.17/14.14 mm²) nerves. The optimum CSA- receiver operating characteristic (ROC) points and sensitivities/specificities were, respectively, 6.85 mm² and 68-85% for the PT point, 7.35 mm² and 71-78% for the T point, 6.75 mm² and 62-75% for the M nerve and 9.55 mm² and 81-72% for the CF nerve. The ΔCSAs of the LPs were greater than those of the HVs at the PT point (4.02/0.85; p = 0.007), T point (3.71/0.98; p = 0.0005) and CF nerve (2.93/1.14; p = 0.015), with no difference found for the M nerve (1.41/0.95; p = 0.17). The optimum ΔCSA-ROC points, sensitivities, specificities and p-values were, respectively, 1.35, 49%, 80% and 0.003 at the PT point, 1.55, 55-85% and 0.0006 at the T point, 0.70, 58-50% and 0.73 for the M nerve and 1.25, 54-67% and 0.022 for the CF nerve. The ΔTPT in the LPs was greater than that in the HVs (4.43/1.44; p <0.0001). The optimum ΔTPT-ROC point was 2.65 (90% sensitivity/41% specificity, p < 0.0001). The ROC analysis of CSAs showed the highest specificity and sensitivity at the PT point and CF nerve, respectively. The PT and T ΔCSAs had high specificities (> 80%) and ΔTPT had the highest specificity (> 90%). New sonographic peripheral nerve measurements (ΔCSAs and ΔTPT) provide an important methodological improvement in the detection of leprosy neuropathy.