Echotexture of peripheral nerves: correlation between US and histologic findings and criteria to differentiate tendons.

To correlate the histologic structure and echotexture of peripheral nerves and verify if ultrasound (US) findings can be used to differentiate nerve from tendon.In an in vitro study, the echotexture of normal peripheral nerves was correlated with the histologic findings. In an in vivo study, US was used to differentiate median nerve from flexor pollicis longus tendon in healthy volunteers (12 male and eight female subjects 7-68 years of age; mean age, 35 years).US examination of the peripheral nerve specimens showed hypoechoic areas separated by hyperechoic bands. The hypoechoic areas corresponded to neuronal fascicles at histologic examination. This fascicular pattern was clear in all median and ulnar nerves, 15 of 20 vagus nerves, and 19 of 20 sciatic nerves in the volunteers but not in recurrent laryngeal nerves.Peripheral nerves have a typical US pattern that correlates with histologic structure and facilitates differentiation between nerves and tendons.