Lymphatics of neck:
Six levels are currently used to describe the complete
nodal anatomy of neck. The concept of sublevels has been introduced
into the classification because certain zones have been identified
within the six levels, which may have clinical significance.
Level I lymphatics: This has been further subdivided into two sublevels.
Sublevel IA (submental) includes nodes within the submental triangle. This
triangle is bounded by the anterior bellies of digastric muscles and the Hyoid
Sublevel IB (Submandibular): This level includes lymph nodes within the boundaries
of anterior belly of digastric muscle, the stylohyoid muscle, and inferior border
of the body of the mandible.
Level II lymphatics: (Upper jugular) This includes nodes located around the upper
third of the internal jugular vein and spinal accessory nerve. This extends from
the skull base above to the inferior border of hyoid bone below. The anterior boundary
is the stylohyoid muscle, and the posterior boundary is the posterior border of
sternomastoid muscle. Two sublevels have been identified in this level.
Sublevel IIA: Includes nodes located anterior to the vertical plane defined by the
spinal accessory nerve.
Sublevel IIB: Includes nodes located posterior to the vertical plane defined by the
spinal accessory nerve.
Level III: Midjugular nodes - includes nodes located around the middle third of the
internal jugular vein extending from the inferior border of the Hyoid bone above to
the inferior border of cricoid cartilage below. The anterior (medial) boundary is
the lateral border of the sternohyoid muscle, and the posterior (lateral) boundary is
the posterior border of sternocleidomastoid muscle.
Level IV: Lower jugular nodes - Includes nodes located around the lower third of
internal jugular vein extending from the inferior border of the cricoid cartilage
above to the clavicle below.
Level V: Posterior triangle: includes nodes located along the lower half of the
spinal accessory nerve and the transverse cervical artery. The supraclavicular nodes
are also included in the posterior triangle group. The superior boundary of this level
is the apex formed by convergence of sternomastoid and trapezius muscles. A horizontal
plane marking the inferior border of the anterior cricoid arch separates level V into
two sublevels. Sublevel VA lie above this plane. This plane includes spinal accessory
nodes. Sublevel VB lie below this plane. This level includes the nodes that follow
the transverse cervical vessels and the supraclavicular nodes with the exception of
Virchow node which is located in level IV.
Level VI: Anterior compartment: Nodes in this compartment include thee pre and paratracheal
nodes, precricoid (Delphian node), and the perithyroidal nodes including the nodes
along the recurrent laryngeal nerves. The superior boundary is the hyoid bone, the inferior
boundary is the suprasternal notch. The lateral boundaries are the common carotid
Nodes not included in these levels should be referred to by the name of their specific
nodal group; these include superior mediastinal group, retropharyngeal group, periparotid
group, buccinator group, post auricular group and suboccipital group of nodes.