Ultrasound reference values for peripheral nerve cross-sectional areas and indices in a sample of healthy individuals in Brazil

Abstract

Objective: To establish peripheral nerve cross-sectional area (CSA) reference values (absolute values, measures of asymmetry, and measures of focality) for healthy individuals in Brazil. Materials and Methods: Sixty-six healthy volunteers underwent high-resolution ultrasound of the peripheral nerves. We obtained CSA measurements for three peripheral nerves, at specific locations: the median nerve, in the carpal tunnel (MT); the ulnar nerve, at the cubital tunnel site (UT) and at the pre-tunnel site (UPT); and the common fibular nerve, near the fibular head (FH). We calculated the CSA indices between the same sites on different sides (∆CSAs) and between the ulnar nerve tunnel and pre-tunnel sites on the same side (∆TPT). Results: A total of 132 neural sites were analyzed, and the following CSA values (mean ± SD, median) were obtained: MT (6.3 ± 1.9 mm2, 6.0 mm2); UT (6.2 ± 1.6 mm2, 6.1 mm2); UPT (5.6 ± 1.7 mm2, 5.4 mm2); and FH (10.0 ± 3.7 mm2, 9.9 mm2). The ∆CSA values (mean ± SD, median) were as follows: MT (0.85 ± 0.7 mm2, 0.95); UT (0.81 ± 0.62 mm2, 0.95); UPT (0.61 ± 0.51 mm2, 0.5); and FH (1.0 ± 0.77 mm2, 1.0). The ∆TPT (mean ± SD, median) was (1.0 ± 0.8 mm2, 1.0). Conclusion: Among individuals in Brazil, peripheral nerve CSA values tend to be higher among males and to increase with aging. However, the same does not appear to hold true for the ∆CSA or the ∆TPT, the exception being the difference between the right and left UT. Differences in CSA values greater than 2.5 mm2 between sides or between sites along the same nerve can indicate asymmetry or focal thickening in neuropathy, respectively.

Imaging evaluation of peripheral nerves

“…Although in many cases magnetic resonance imaging (MRI) continues to be the gold standard for nerve imaging, especially for the identification of deep nerves, ultrasound has become an essential imaging technique because of its ability to offer dynamic information, its more widespread availability, and its lower cost (in comparison with MRI) (1) . I totally agree with Voltan et al (2) , as published in the previous issue of Radiologia Brasileira, that high-resolution ultrasound provides information complementary to that obtained by electroneuromyography, especially on the morphology of nerve fascicles and the vascularization of peripheral nerves. Those authors also stated that, as well as being noninvasive and rapidly executed, high-resolution ultrasound can be used in order to assess neural dimensions, locate compression zones within fibrous tunnels, identify tumors, and diagnose traumatic pathologies (2) .…”

“…I totally agree with Voltan et al (2) , as published in the previous issue of Radiologia Brasileira, that high-resolution ultrasound provides information complementary to that obtained by electroneuromyography, especially on the morphology of nerve fascicles and the vascularization of peripheral nerves. Those authors also stated that, as well as being noninvasive and rapidly executed, high-resolution ultrasound can be used in order to assess neural dimensions, locate compression zones within fibrous tunnels, identify tumors, and diagnose traumatic pathologies (2) . Given the lack of data on this topic in the literature, it is important that the authors demonstrated that the peripheral nerve cross-sectional areas were lower in a sample of the Brazilian population than in most of the other samples described in the literature.…”

Silent peripheral neuropathy determined by high-resolution ultrasound among contacts of patients with Hansen's disease

“…For comparison of the values obtained for the patients, we considered the values established by Voltan et al ( 54 ) as normality standards (healthy individuals—none of whom had any known contact with leprosy) for CSAs in the Brazilian population.…”

“…The nerves were considered to be enlarged when their CSA was greater than the mean ± 2 SD of the normal values established in the study by Voltan et al ( 54 ).…”

“…All of them were Brazilian volunteers to be submitted to peripheral nerve ultrasound. As a comparative sample of healthy Brazilian volunteers, we used 49 healthy individuals (HVs) among the cases of our service, and as a comparative sample of patients diagnosed with HD (HD), we used cases of our service as published by Voltan et al ( 53 , 54 ).…”