THU0494 RELATIONSHIP BETWEEN THE AREA OF THE MEDIAN NERVE CROSS SECTION AND THE CIRCUMFERENCE OF THE CARPUS AS A DIAGNOSTIC TOOL FOR CARPAL TUNNEL SYNDROME
Authors: Carlos Guillén-Astete, Patricia García-Casado
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> The diagnosis of carpal tunnel syndrome (CTS) is fundamentally electrophysiological, however, on diagnostic suspicion ultrasonography has been shown to correlate satisfactorily with the electromyogram. The limitations of the ultrasound study of the median nerve in patients with STC are due to the fact that the intervals of normality of the area of the median nerve cross section (ACTNM) are variable according to the sources consulted, the sex and the anthropometry of the individual. <h3>Objectives</h3> The purpose of this study is to determine whether NMTA can be correlated with a simple measurement such as wrist circumference length (MCL) in patients with electrophysiological diagnosis of TCEs and healthy subjects and used to discriminate them better than with the simple measurement of NMTA. <h3>Methods</h3> We included 50 patients with electrophysiological diagnosis of CTS and 43 healthy subjects of white ethnicity, older and with different anthropometric characteristics. The patients came from the Rheumatology consultations of three different centres. Healthy volunteers were subjects without CTS clinic, thyroid alterations, diabetes or known autoimmune rheumatological diseases whose data were obtained from a previous study. Circumference was measured with a flexible tape measure around the carpus immediately distal to the interstylloid line. The ultrasound measurements were made at the height of the escofoid and pisciforme bones using three different ultrasound scanners according to the headquarters: Toshiba Nemio XG, 13Mhz linear probe, Samsung HM70a 14 MHz and Logiq e GE 12 MHz. All the measured images were captured for analysis and correction of circumference lengths by an observer not linked to the identity of the subjects nor to their character of patient or control. An association study between wrist circumference and ACTNM was performed for both groups and a correlation index was submitted to a validation test for the determination of sensitivity and specificity. <h3>Results</h3> ACTNM was 11.11 SD 1.18mm2 in the control group and 12.73 SD 1.50mm2 in the patient group (p&lt;0.05). The LCM was 18.81 DE 1.50cm and 18.72 DE 1.85 (p=0,803). In healthy subjects, the correlation between ACTNM and carpal circumference showed a satisfactory correlation (Coef Pearson 0.809, p&lt;0.01, bilateral) as well as in patients (Coef Pearson 0.878, p&lt;0.01, bilateral). The ACTNM/LCM index in the control group was 0.590 and for the patient group 0.679 (p&lt;0.01). The area under the ACTNM curve was 0.808 EE 0.049 while in the case of the ACTNM/LCM index was 0.954 EE 0.019. The area under the ACTNM curve was 0.808 EE 0.049 while in the case of the ACTNM/LCM index was 0.954 EE 0.019. With an index of 0.62 or a sensitivity of 93% and specificity of 78% are obtained for the diagnosis of CTS. <h3>Conclusion</h3> LCM correlates well with ACTNM in healthy patients. It could be considered a good anthropometric marker for further studies of normal ultrasound ranges of the median nerve. The LCM/ACTNM index is a useful measure to discriminate controls of patients with electrophysiological diagnosis of JTS. In our series, this index exceeds the discriminatory capacity of the ACTNM as an individual measure. <h3><b>Disclosure of Interests:</b>&nbsp;</h3> None declared&nbsp;