Ultrasound image of the interscalene area after the injection of local anesthetic. The bevel of the Tuohy needle (arrow) was visualized between the C5 and C6 nerve roots. The interscalene space had been expanded with 20 ml of local anesthetic. AS: anterior scalene muscle, MS: middle scalene muscle, SCM: sternocleidomastoid muscle, ISS: interscalene space.