Intra- and Inter-Observer Variability in Sonographic Measurement of the Cervical Nerve Roots of Healthy Volunteers

Abstract

Aim: The aim of our study is to determine the normal values of mean cervical (C) nerve root diameter in millimeters (mm) in healthy volunteers and to show its relationship to age, gender, height, weight, body mass index (BMI), and the dominant hand.Material and Method: Two observers measured the mean nerve root diameter of the bilateral C5, C6, and C7 nerve of all volunteers. Before the procedure, the age, sex, height, weight, BMI, and the dominant hand of all the participants were noted. Two measurements were taken by each of the two observers without one knowing about the other’s noted values. The intraclass correlation coefficient (ICC) test was used to analyze intra-and inter-observer reliability.Results: There was no statistically significant relationship between gender and dominant hand, and mean nerve root diameter. Moreover, when we compared the mean nerve root diameter for the nerves in the right and left sides of each participant, no significant statistical differences were identified. The mean diameter of the C6 nerve root was higher than that of C7, which was higher than that of C5 on both sides (p < 0.001). The ICC values for intra- and inter-observer were good or excellent for all diameter measurements (ICC > 0.8).Conclusions: The normal range of cervical nerve root diameters should be determined to distinguish pathological conditions. In our study, the measurement of mean nerve root diameters of C5, C6, and C7 nerves is highly reproducible with excellent intra-observer and inter-observer agreement. Therefore, the measurement of nerve root diameter can be confidently performed in daily clinical practice.