Ultrasonographic Findings of the Normal Nerves in Common Entrapment Site; Cross-Sectional Area Reference Value and Normal Variant

Background: Neuromuscular ultrasound has emerged over the last decade as a useful tool for diagnosing peripheral neuropathy.Because nerve enlargement is the most important diagnostic marker of an abnormal nerve, quantification of nerve size is essential.Methods: We included 80 healthy volunteers aged 21-60 years.The nerve cross-sectional area (CSA) was measured in all participants at the following common compressive sites: bilateral median nerve at the carpal tunnel and forearm, ulnar nerve at the wrist and medial epicondyle, radial nerve at the spiral groove, peroneal nerve at the fibular head and popliteal fossa, and tibial nerve at the popliteal fossa.Anatomical variants were also evaluated, including a bifid median nerve and persistent median artery.Results: The CSAs were 9.58±1.55,6.87±1.61,4.72±0.91,6.64±1.33,6.48±1.68,12.35±3.55,and 26.98±6.92mm 2 (mean±SD) for the median nerve at the carpal tunnel and forearm, ulnar nerve at the wrist and medial epicondyle, radial nerve at the spiral groove, peroneal nerve at the fibular head, and tibial nerve at the popliteal fossa, respectively.The nerve CSA was significantly larger in men than in women and was correlated with body mass index, weight, and height.A bifid median nerve and persistent median artery were seen in 12 (7.5%)and 4 (2.5%) of 160 hands, respectively. Conclusions:The information produced in this study can serve as reference data when evaluating these nerve sites using ultrasound.