Triangles and Lymph node levels of Neck

There are 2 major triangles in the neck, containing other smaller triangles.

neck triangles — 1 – parotid gland; 2 – submandibular gland; 3a – superior belly of omohyoid; 3b – inferior belly of omohyoid; 4 – sternohyoid; 5 – sternal head of SCM; 5b – clavicular head of SCM; 6 – EJV; 7 – greater auricular nerve

1. Anterior triangle: Midline of neck – Mandible – Anterior border of SCM

Submental triangle: IA (Submental LN)
Submandibular or Digastric triangle: IB (Submandibular LN), Submandibular gland, CN XII
Carotid triangle: II + III, Carotid sheath (CCA, IJV, XN X)
Muscular triangle: IV, Infrahyoid muscles, Thyroid and Parathyroid glands

Posterior triangle: Posterior border of SCM – Trapezius – Clavicle (level V); 2 triangles inside separated by inferior belly of omohyoid

Occipital triangle: OT GLASS
- Occipital artery
- Transverse cervical artery and vein
- Greater auricular nerve (C2, C3)
- Lesser occipital nerve (C2)
- Accessory spinal nerve (CN XI)
- Supraclavicular nerve (C3, C4)
- Small muscular branches: Levator scapulae (C3, C4), Trapezius (C3, C4), Rhomboideus (C5)
Supraclavicular or Subclavian triangle:
- 3 trunks of brachial plexus
- Nerves arising from roots and trunks of brachial plexus:
  - Long thoracic nerve (C5, C6, C7) – serratus anterior
  - Nerve to subclavius (C5, C6)
  - Suprascapular nerve (C5, C6)
- Subclavian artery (3rd part) and Subclavian vein
- Suprascapular artery and vein
- External jugular vein (lower part)

Lymph node levels of neck — Visual mnemonic or schematic diagram showing boundaries of lymph node levels or zones of neck

Surgically, cervical lymph nodes are divided into 6-7 levels (only 6 according to many authors who exclude the level VII nodes) for staging of carcinoma which would also be the basis for selective neck dissection. There are 5 levels in the lateral compartment and 2 in the central compartment. Nodes not included in these system of levels are retropharyngeal group, periparotid group, buccinator group, post auricular group and suboccipital group of nodes.

Level		Lymph nodes	Boundaries
I	A	Submental nodes	Bilaterally: Anterior belly of digastrics Inferiorly: Hyoid bone
	B	Submandibular nodes	Superiorly: Mandible Posteroinferiorly: Posterior belly of digastrics Anteroinferiorly: Anterior belly of digastrics
II	A (Anterior to the vertical line in relation to spinal accessory nerve)	Upper internal jugular (deep cervical) nodes	Superiorly: Skull base Inferiorly: Inferior border of hyoid bone and Carotid bifurcation Posteriorly: Posterior border of Sternocleidomastoid (SCM) Anteriorly: Lateral border of Sternohyoid and Stylohyoid
	B (Posterior to the vertical line in relation to spinal accessory nerve)
III		Mid internal jugular (deep cervical) nodes	Superiorly: Inferior border of hyoid bone and Carotid bifurcation Inferiorly: Inferior border of cricoid cartilage and Junction of omohyoid muscle and IJV Posteriorly: Posterior border of SCM Anteriorly: Lateral border of sternohyoid
IV		Lower internal jugular (deep cervical nodes)	Superiorly: Inferior border of cricoids cartilage and Junction of omohyoid and IJV Inferiorly: Clavicle Posteriorly: Posterior border of SCM Anteriorly: Lateral border of sternohyoid
V	A (Above the horizontal plane marking the inferior border of arch of cricoids cartilage)	Posterior triangle (spinal accessory) nodes	Superiorly: Convergence of SCM and trapezius Inferiorly: Clavicle Posteriorly: Anterior border of trapezius Anteriorly: Posterior border of SCM
	B (Below the horizontal plane marking the inferior border of arch of cricoids cartilage)
VI (Prelaryngeal or Delphian, Pretracheal, Paratracheal, Prethyroidal)		Anterior compartment (midline) nodes	Superiorly: Hyoid bone Inferiorly: Suprasternal notch Bilaterally: Carotid arteries
VII		Upper mediastinal nodes	Below suprasternal notch

The highest jugular digastric node near the angle of the mandible is called the “sentinel” node.
The “signal” node is the lowest along the internal jugular chain called the virchow nodes.