Fig. 2

US examination findings. a Ultrasonography was performed using a Canon Aplio i800 with a 24-MHz linear probe. Preoperatively, the SAN was swollen (1.8-mm width) at the central sternocleidomastoid muscle level within the posterior cervical triangle, but nerve continuity was preserved. The diameter of the SAN gradually improved from 1.8 mm preoperatively to 1.3 mm at 3 months (b) and 0.9 mm at 6 months (c), at which time there was no swollen area