Last's Anatomy: Regional and Applied

Part fifteen. Lymph drainage of head and neck

All the lymph drainage from the head and neck goes to the deep cervical nodes. They receive afferents from other lymph node groups in the head and neck as well as directly from organs in these regions. Efferents from the deep cervical nodes form the jugular trunk which on the left drains into the thoracic duct and on the right into the right lymphatic duct. The thoracic duct and the right lymphatic duct usually empty into the junction of the subclavian and internal jugular veins on their respective sides; otherwise they open into either of these veins.

There is a horizontal, encircling band of lymph node groups at the craniocervical junction. Nodes in all these groups are clinically palpable when enlarged. Submental nodes lie across the midline, below the chin in the submental triangle (see p. 344). The other lymph node groups in the horizontal band are bilaterally represented. Submandibular nodes lie in the digastric triangle in relation to the submandibular salivary gland (see p. 338). Preauricular nodesare found both superficial and deep to the fascial capsule of the parotid, as well as within the gland (see p. 359). A small mandibular node is frequently present where the facial vessels cross the lower border of the mandible, and a small buccal node may lie on the lateral surface of the buccinator. One or two mastoid (postauricular) nodes lie on the mastoid process and two or three occipital nodes are present at the apex of the posterior triangle of the neck (see p. 333). The organs and areas that drain to all these nodes are mentioned in connection with the descriptions of the relevant regions.

A few superficial cervical nodes lie along the external jugular vein, on the superficial surface of the sternocleidomastoid, and drain the lobule of the auricle, floor of the external acoustic meatus and skin over the lower parotid region, as well as the lateral cervical skin. Anterior cervical skin drains to a few superficially located anterior cervical nodes along the anterior jugular veins; one such node frequently lies in the suprasternal space.

Deep to the investing fascia at the front of the neck are infrahyoid nodes lying on the thyrohyoid membrane, prelaryngeal nodes on the cricothyroid membrane and pretracheal nodes on the tracheal rings. They drain the anterior cervical nodes and receive lymph from the larynx, trachea and thyroid gland. Paratracheal nodes on either side of the trachea and oesophagus receive lymph from pretracheal nodes and directly from the trachea and oesophagus. Retropharyngeal nodes lie posterior to the pharynx and anterior to the prevertebral fascia. They drain the pharynx, soft palate, posterior parts of hard palate and nose, and the cervical vertebrae. When enlarged, these nodes can cause difficulty in swallowing (dysphagia) due to pressure on the pharynx.

Many of the deep cervical nodes are closely related to the internal jugular vein, some within the carotid sheath, some on the surface of the sheath. They are descriptively divided into upper and lower groups (superior and inferior deep cervical nodes) and are mainly under cover of the sternocleidomastoid. Some nodes of the lower group extend into the lower part of the posterior triangle and are related to the brachial plexus and subclavian vessels; these are also termed supraclavicular nodes. One or two nodes lie in contact with the accessory nerve at a higher level in the posterior triangle. One or two nodes of the upper group of deep cervical nodes, the jugulodigastric nodes, lie behind the posterior belly of the digastric in front of the internal jugular vein (Fig. 6.63). When enlarged, as a result for instance of pathology in the palatine tonsil, these are easily palpable behind and below the angle of the mandible. The jugulo-omohyoid node is a lower group node that lies above the intermediate tendon of omohyoid posterior to the internal jugular vein. All the lymph drainage from the tongue is believed to reach this node on the two sides of the neck before entering the jugular trunks. The node lies deep to sternocleidomastoid and needs to be considerably enlarged to be clinically palpable.

Surgical approach

Surgeons treating malignant lymph nodes in the neck tend to classify them by levels. Level I nodes are in the submental and submandibular triangles. Level II–IV nodes are deep cervical nodes, Level II being from the base of the skull to the carotid bifurcation (hyoid bone), Level III from there to the intermediate tendon of omohyoid (cricoid cartilage), and Level IV from there down to the clavicle and including the supraclavicular nodes. Level V nodes are in the posterior triangle of the neck, related to the accessory nerve. Level VI nodes are nodes surrounding the midline visceral structures and include the pretracheal and paratracheal nodes. Level VII nodes are in the superior mediastinum. Classical radical neck dissection removed Level I–V nodes with the sternocleidomastoid muscle, internal jugular vein and accessory nerve. Modified radical neck dissection (also called functional neck dissection) preserves some or all of these latter three structures. Selective neck dissection removes some but not all Level I–V nodes.