Evaluating the Mean Cross-Sectional Area (CSA) of Median Nerve by Use of Ultrasound in Thai Population
Boontaree Wanitwattanarumlug MD*, Vithya Varavithya MD*
Affiliation : *Department of Radiology, Faculty of Medicine, Srinakharinwirot University, Nakhon Nayok, Thailand
Background : The diagnosis of carpal tunnel syndrome (CTS) is usually based on clinical combining with nerve conductive
study (NCS). Recently, ultrasound (US) is the choice for investigation of median nerve morphology and size. The advantages
of US are non-invasive in nature and no discomfort or pain. Data on median nerve cross sectional area (CSA) in healthy Thai
subjects are still limited.
Objective : To know the mean value of normal CSA in healthy Thai population. Is it different from the other countries?
Material and Method: 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 antero-
posterior diameter were recorded.
Results : 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.
Conclusion : Although body habitus of people was different among countries, the mean CSA of median nerve in healthy people
are not significantly difference.
Keywords : Ultrasound, Mean cross-sectional area (CSA), Median nerve
