Journal of the Medical Association of Thailand Vol 95, No 12:DECEMBER 2012 (SUPPL. 12) 0125-2208 95 12 2012 Dec Evaluating the Mean Cross-Sectional Area (CSA) of Median Nerve by Use of Ultrasound in Thai Population 21 EN Boontaree Wanitwattanarumlug Vithya Varavithya Original Article To know the mean value of normal CSA in healthy Thai population. Is it different from the other countries? Thai populations, without clinical sign or symptom of CTS, were included in the present study. A linear array transducer was used to scan and measure median nerve cross sectional area and the maximum transverse and anteroposterior diameter were recorded. Eighty-eight wrists of 44 asymptomatic of CTS and healthy Thai volunteer were examined with US. The mean CSA measurement were found as 6.83 + 0.98 mm2 by tracing method (TM) and 6.81 + 1.12 mm2 by ellipsoid formula (EF) method. No significant differentiation was observed between CSA calculated using TM and EF of median nerve. There was no significant difference in CSA between right and left hand or dominate and non-dominate hand. CSA calculated by the TM and EF method were found to be significantly larger in male than in female. There was no correlation between CSA and age or BMI. Although body habitus of people was different among countries, the mean CSA of median nerve in healthy people are not significantly difference. Ultrasound Mean cross-sectional area (CSA) Median nerve