Marcello Henrique Nogueira-Barbosa MD, PhD, Presenter: Nothing to Disclose

Everaldo Gregio-Junior, Abstract Co-Author: Nothing to Disclose

Michel D. Crema MD, Abstract Co-Author: Shareholder, Boston Imaging Core Lab, LLC

Ricardo Noda Navarro MD, Abstract Co-Author: Nothing to Disclose

Theo Pavan, Abstract Co-Author: Nothing to Disclose

Antonio Adilton Carneiro, Abstract Co-Author: Nothing to Disclose

Ultrasound elastography may differentiate soft tissues based on distinct deformation under mechanical pressure. This technique has been applied to evaluate tissues such as tendons, breast and liver, but little information is known regarding peripheral nerves. The aim of this study was to access the feasibility and reproducibility of real-time freehand ultrasound elastography (RFUE) of the median nerve in asymptomatic volunteers.

After Institutional Ethics Committee approval, 100 median nerves from 50 consecutive asymptomatic volunteers (24 men, 26 women; mean age, 32.3 years; range, 18–79 years) were evaluated with RFUE (Sonix RP, Ultrasonix Medical Corporation). The evaluation of strain ratio between the median nerve and flexor superficialis digitorum muscle (FDSM) was made 6 cm proximally from the proximal cutaneous fold of the wrist. Measurements were performed on the transverse plane by two radiologists, separately and independently. Qualitative evaluation represented the stiffness index of the median nerve tissue compared to the FDSM, based on the colors of the strain images. Inter- and intra-observer reproducibilities for qualitative evaluation were assessed using weighted kappa (κ) statistics, and for strain ratio measurements were assessed using intraclass correlation coefficients (ICC).

The mean strain ratio was 3.58 ± 1.15 (observer 1) and 3.59 ± 1.19 (observer 2). No significant differences were found for the strain ratio regarding gender (p=0.67) as well as right and left sides (p=0.10). The inter-observer reproducibility of strain ratio varied from 0.10 (95% CI -0.19-0.37) to 0.35 (95% CI 0.08-0.57) and intra-observer varied from 0.34 (95% CI 0.22-0.40) to 0.40 (95% CI 0.28-0.52). Regarding the qualitative assessment, the inter-observer agreement was 0.45 (95% CI 0.22-0.67) and intra-observer agreement values varied from 0.70 (95% CI 0.54-0.85) to 0.48 (95% CI 0.26-0.70).

Median nerve was consistently stiffer than the adjacent FSDM on qualitative classification and on strain ratio measurements. Qualitative assessment of the median nerve on elastograms showed moderate to substantial agreement. Reproducibility of strain ratio was fair to moderate.

Because inflammatory pathology affecting the nerve may have the potential to change its stiffness, the knowledge of normal elastographic parameters may help in diagnosing median nerve disorders

Nogueira-Barbosa, M, Gregio-Junior, E, Crema, M, Navarro, R, Pavan, T, Carneiro, A, Feasibility and Reproducibility of Real-Time Freehand Ultrasound Elastography of the Median Nerve in Asymptomatic Volunteers.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12027983.html