label: Neck Lymph Node Boundary Level II
label_lc: neck lymph node boundary level ii
description: "Neck lymph node boundary level II contains the upper jugular nodal group. It is divided by the accessory nerve into sublevels IIA and IIB. The following anatomical structures define sublevel IIA: Superior: skull base; inferior: horizontal plane defined by the inferior border of the hyoid bone; anterior (medial): stylohyoid muscle; posterior (lateral): vertical plane defined by the spinal accessory nerve. The following anatomical structures define sublevel IIB: Superior: skull base; inferior: horizontal plane defined by the inferior body of the hyoid bone; anterior (medial): vertical plane defined by the spinal accessory nerve; posterior (lateral): lateral border of the sternocleidomastoid muscle. (partially adapted from AJCC 8th ed.)"