Carpel tunnel syndrome (CTS) is the most common mononeuropathy with a significant morbidity and good treatment outcome. Several studies from around the world reported that the high-resolution ultrasound (US) becomes the first line noninvasive technique in diagnosis of CTS by measurement of the cross-sectional area (CSA) of the median nerve (MN) proximal to the site of entrapment and with variable cut-off value = 9-11 mm2. According to various studies, it is both sensitive (82% - 89%) and

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... c (83% - 97%) for the diagnosis of CTS. in comparison with nerve conduction studies (NCS). Nerve swelling showed the highest accuracy (91%) among gray-scale ultrasound. The aims of this study were to determine the CSA of the MN among Libyan population and to confirm the accuracy of high-resolution ultrasound in diagnosis of the CTS in comparison with NCS. A case-control study was performed during 2018 at Radiology Department - AL-Hawari General Hospital by Radiologist using high-resolution ultrasound. The number of patients was 57 and the number of wrists studied of these patients was seventy wrists presented with unilateral or bilateral symptoms of CTS examined by US and their NCS were performed. A control group of 200 wrists of 100 healthy subjects were included to determine the median nerve CSA cut-off in the Libyan population. The cut-off point for Median nerve CSA in the Libyan patients = <9 mm2 was considered in-patient with CTS. CTS were bilateral in 13 cases and unilateral in 44 cases. Ultrasound examination for the diagnosis of CTS is painless, cost effective, tolerable to patients comparing to the NCS and measurement of the median nerve cross-sectional area is both sensitive and specific for such purpose. It is recommended that the high-resolution ultrasound examination should be used as a first line test for the diagnosis of CTS.