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TableĀ 1 Anatomical structures defining the boundaries of the cervical levels and sublevels

From: Occipital lymph node metastasis from nasopharyngeal carcinoma: a special case report and literature review

Boundary level Superior Inferior Anterior (medial) Posterior (lateral)
IA Symphysis of mandible Body of hyoid Anterior belly of contralateral digastric muscle Anterior belly of ipsilateral digastric muscle
IB Body of mandible Posterior belly of diagastric muscle Anterior belly of digastric muscle Stylohyoid muscle
IIA Skull base Horizontal plane defined by the inferior border of the hyoid bone The stylohyoid muscle Vertical plane defined by the spinal accessory nerve
IIB Skull base Horizontal plane defined by the inferior body of the hyoid bone Vertical plane defined by the spinal accessory nerve Lateral border of the sternocleidomastoid muscle
III Horizontal plane defined by the inferior body of hyoid Horizontal plane defined by the inferior border of the cricoid cartilage Lateral border of the sternohyoid muscle Lateral border of the sternocleidomastoid or sensory branches of cervical plexus
IV Horizontal plane defined by the inferior border of the cricoid cartilage Clavicle Lateral border of the sternohyoid muscle Lateral border of the sternocleidomastoid or sensory branches of cervical plexus
VA Apex of the convergence of the sternocleidomastoid and trapezius muscles Horizontal plane defined by the lower border of the cricoid cartilage Posterior border of the sternocleidomastoid muscle or sensory branches of cervical plexus Anterior border of the trapezius muscle
VB Horizontal plane defined by the lower border of the cricoids cartilage Clavicle Posterior border of the sternocleidomastoid muscle Anterior border of the trapezius muscle
VI Hyoid bone Suprasternal notch Common carotid artery Common carotid artery
VII Suprasternal notch Innominate artery Sternum Trachea, esophagus, and prevertebral fascia