Ultrasound image of the C6 transverse short-axis view following left SGB at the C6 level. Arrows show the subfascial spread of local anesthetics above the longus colli muscle. The fine long arrow indicates the out-of-plane needle path. CA: carotid artery, LCo: longus colli muscle, SCM: sternocleidomastoid muscle, Thy: thyroid gland, T: Chassaignac's tubercle, med: medial, lat: lateral.