Modified inferior C6 transverse process level. AM, anterior scalene muscle; SCM, sternocleidomastoid muscle; C6, the 6th cervical nerve root; PF, anterior vertebral fascia; LCM, long neck muscle; ⋆Indicates stellate ganglion block area; ↘Indicates simulated puncture path; IJV, internal jugular vein; CA, carotid artery.