The history of the neck dissection for head and neck cancer stretches back nearly two centuries. Even in the early 19th century, physicians were aware of the poor prognosis associated with cervical metastases in head and neck cancer. Other surgeons had advocated for the removal of the lymphatic tissue of the neck, but it was described en bloc resection of the cervical lymph nodes for a clinically positive nodal disease that is credited with the first description of the technique. The procedure removed all lymph nodes in the lateral neck (now known as levels I-V) and the spinal accessory nerve (CN XI), internal jugular vein (IJV), sternocleidomastoid muscle (SCM) along with several other surrounding structures. However, this procedure resulted in significant cosmetic deformity and loss of function.
Over time, the procedure has been modified to reduce morbidity while maintaining oncologic efficacy. The modified radical neck dissection, which advocated for the preservation of at least one of the critical non-lymphatic structures (CNXI, IJV, or SCM) was proposed by Drs. Bocca and Suarez independently in the 1960s.
Studies detailing the lymphatic drainage pathways of various head and neck regions further altered the classical radical neck dissection allowing for dissection of limited lymph node basins of the neck based on tumor location. As anatomic and oncologic understanding has improved, the neck dissection has become increasingly narrow in scope. Prophylactic neck dissections are also utilized for any clinically negative head and neck tumor that has a greater than 20% chance of having occult metastasis to the neck.
In 2002, the American Academy of Otolaryngology-Head and Neck Surgery proposed a standardized classification system for naming the various neck dissections in use which is still in use today. The radical neck dissection refers to the removal of levels I-V along with the SCM, IJV, and CN XI. The modified radical neck dissection also removes levels I-V but spares at least one non-lymphatic structure (SCM, IJV, or CN XI). The selective neck dissection refers to any procedure which removes one or more levels of the neck based on patterns of cervical metastasis. Finally, an extended neck dissection refers to any neck dissection that removes additional structures of lymph nodes from areas not addressed in radical neck dissection.
The neck is a complex and dense anatomical area. A thorough understanding of the critical structures, fascial layers, and cervical lymph node drainage patterns in the neck is key to performing safe and oncologically sound surgery.
The lymph nodes in the neck are divided into seven levels by anatomic landmarks. These are based upon anatomic studies delineating drainage pathways from different head and neck subsites.
Boundary: Level IA (a midline structure) is bordered by the bilateral anterior digastric muscles laterally, the hyoid inferiorly, and the mandible superiorly. Level IB is bordered by the anterior digastric muscle anteriorly, the posterior digastric muscle posteriorly, the posterior edge of the submandibular glands laterally, and the mandible superiorly.
Key structures and relationships: The lingual nerve, hypoglossal nerve, submandibular duct, and facial artery and vein are all found in level I. The only significant structure found lateral to the posterior belly of the digastric is the facial vein. The marginal mandibular branch of the facial nerve can be found in the fascia overlying the submandibular gland superficial to the facial vessels.
Boundary: Level IIA is bounded by CN XI posteriorly, the posterior edge of the submandibular gland anteriorly, the skull base superiorly, and the hyoid inferiorly. Level IIB is bounded by the posterior edge of the SCM laterally, CN XI anteriorly, the skull base superiorly, and the hyoid inferiorly.
Key structures and relationships: Level II is divided into two parts by CN XI. Cranial nerve XI runs deep to the posterior digastric muscle and the occipital artery. The majority of the time, CN XI runs superficial to the IJV, but it may also run deep or through the IJV as well. CN XI often gives off a small branch to the trapezius prior to entering the SCM.
Boundary: Level III is bounded by the posterior border of the SCM laterally, the lateral border of the sternohyoid medially, the hyoid superiorly, and the inferior border of the cricoid cartilage inferiorly.
Key structures and relationships: The phrenic nerve runs deep to the cervical rootlets and superficial to the anterior scalene muscle beneath the deep layer of the deep cervical fascia.
Boundary: Level IV is bounded by the posterior border of the SCM laterally, the lateral border of the sternohyoid medially, the inferior border of the cricoid superiorly, and the clavicle inferiorly.
Key structures and relationships: From superficial to deep, the structures encountered are the omohyoid, the carotid sheath, thoracic duct (more commonly seen in the left neck), transverse cervical artery, phrenic nerve, and anterior scalene muscle. The lung apices may also be present at the inferior aspect of level IV.
Boundary: Level V is bounded by the trapezius laterally, the lateral border of the SCM medially, and the clavicle inferiorly. A horizontal line extended from the inferior border of the cricoid divides levels VA (superior to cricoid) and VB (inferior to cricoid).
Key structures and relationships: The phrenic nerve is embedded in the fascia overlying the anterior scalenes and can be protected by staying superficial to this plane. The brachial plexus can be found coursing on the floor of level VB between the anterior and middle scalene muscles.
Boundary: Level VI is bounded by the carotid sheaths laterally, the hyoid superiorly, and the sternum inferiorly. Level VI is divided into left and right by the trachea.
Key structures and relationships: The recurrent laryngeal nerve runs through level VI. The right recurrent laryngeal nerve courses more obliquely due to coursing around the innominate artery, while the left nerve has a more vertically oriented course after looping around the aorta. The thyroid and parathyroid glands are also located in level VI.
Boundary: Level VII is bounded superiorly by the inferior border of the suprasternal notch and inferiorly by the innominate artery.
In general, a neck dissection is indicated for any clinically positive nodal disease or advanced tumor stage (T3-T4).
Radical neck dissection is currently reserved only for clinically positive resectable neck disease that involves the SCM, IJV, and CN XI.
The modified radical neck dissection (MRND) is currently the gold standard for clinically positive resectable neck disease. For a neck dissection to fall into this classification, levels I-V must be removed, and at least one of the following structures must be preserved: spinal accessory nerve, sternocleidomastoid muscle, and internal jugular vein. Modified radical neck dissections are classified as type I, II, or III based on which structures are saved. In a type, I MRND CN XI is spared. In type II, MRND CN XI and the IJV are spared. In a type III MRND CN XI, the IJV and the SCM are all spared.
Recently, several studies have demonstrated that clinical outcomes are comparable for modified radical neck dissection and selective neck dissection in select cases.
In patients with clinically negative necks and tumors that place them at high risk of cervical metastasis (greater than 20%), a selective neck dissection is performed of the appropriate nodal basins based on the tumor’s location.
The unresectable disease is an absolute contraindication to performing a neck dissection. This includes invasion of the skull base or deep neck musculature. Carotid artery involvement may be considered either an absolute or relative contraindication to surgery. If the carotid artery may be sacrificed, preoperative evaluation with carotid artery balloon occlusion studies with xenon CT or SPECT-CT imaging should be undertaken to determine the role of carotid reconstruction.
Other relative contraindications include uncompensated coagulopathy, poor overall health with a high risk of anesthetic complications, and poor neurocognitive state. The surgeon should always consider whether an operation may be detrimental to the overall health of the patient due to underlying comorbidities and the inherent stressors of surgery.
The following is a list of key instruments used during neck dissections at the author's home institution. These may be altered to suit the individual preferences of the operating surgeon: