Continuing Education Activity

Head and neck cancers most commonly metastasize initially to the cervical nodal basins. As a result, removing the cervical lymph nodes is an important component of the standard of care for many head and neck cancers. Radical neck dissection refers to removing 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). 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. This activity reviews the indications and procedural steps for radical neck dissection and briefly discusses other variants of neck dissection for head and neck cancer. This activity highlight the role of the healthcare team in managing patients with head and neck cancer.

Objectives:

• Identify the key anatomic relationships in the neck.
• Review the indications for performing radical neck dissection, modified radical neck dissection, and selective neck dissection.
• Explain common complications associated with radical neck dissections.
• Explain the expected clinical outcomes after radical neck dissection, contrasted with modified radical and selective neck dissection.

Introduction

The history of 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 of cervical metastases in head and neck cancer. Other surgeons had advocated for the removal of the lymphatic tissue of the neck, but it was Dr. George Crile’s 1906 article that 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, including the tail of the parotid gland. However, this procedure resulted in significant cosmetic deformity and loss of function.[1] 

Over time, the procedure has been modified to reduce morbidity while maintaining oncologic efficacy. The modified radical neck dissection, which advocated for preserving at least one of the critical non-lymphatic structures (CNXI, IJV, or SCM), was proposed by Drs. Bocca and Suarez independently in the 1960s.[2][3][4]

Studies detailing the lymphatic drainage pathways of various head and neck regions further altered the classical radical neck dissection allowing for the dissection of limited lymph node basins of the neck based on tumor location. As anatomic and oncologic understanding has improved, neck dissection has become increasingly narrow in scope. Prophylactic neck dissections are also utilized for any clinically negative head and neck tumor with a greater than 15 to 20% chance of occult metastasis to the neck.[5][6][7]

In 2002, the American Academy of Otolaryngology-Head and Neck Surgery proposed a standardized classification system for naming the various neck dissections that are still in use today. 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). 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.[8][9]

Anatomy and Physiology

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.

Surgical Levels of the Neck

The lymph nodes in the neck are divided into seven levels by anatomic landmarks. These are based on anatomic studies delineating drainage pathways from different head and neck subsites.  

Level: I (submental and submandibular nodes) 

Boundary:  Level Ia (a midline structure) is bordered by the bilateral anterior bellies of the digastric muscles laterally, the hyoid inferiorly, and the mandible superiorly. Level Ib is bordered by the anterior belly of the digastric muscle anteriorly, the posterior belly of the 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 the facial artery and vein are all found in level I. The only significant structures found lateral to the posterior belly of the digastric are the facial vein and the marginal mandibular nerve. The marginal mandibular branch of the facial nerve can be found in the fascia overlying the submandibular gland, superficial to the facial vessels and deep to the platysma.

Level: II (upper jugular nodes)

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 floor of the neck posteriorly, the skull base superiorly, and the hyoid inferiorly.

Critical 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 (approximately 85%), CN XI runs superficial to the IJV, but it may also run deep (~14%) or through (<1%) the IJV as well.[10] CN XI often gives off a small branch to the trapezius prior to entering the SCM.[11]

Level: III (middle jugular nodes)

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.  

Level: IV (lower jugular nodes)

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, the thoracic duct (more commonly seen in the left neck, though accessory thoracic ducts can be seen in the right neck), transverse cervical artery, phrenic nerve, and anterior scalene muscle. The lung apices may also be present at the inferior aspect of level IV. 

Level: V (posterior triangle nodes)

Boundary: Level V is bounded by the trapezius laterally, the lateral border of the SCM medially, and the clavicle inferiorly. A horizontal line extending 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. 

Level: VI (central compartment nodes) 

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. 

Critical 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.

Level: VII (superior mediastinal nodes)

Boundary: Level VII is bounded superiorly by the inferior border of the suprasternal notch and inferiorly by the innominate artery.

Nodal Drainage Patterns by Head and Neck Subsite

• Oral Cavity: I-III
• Oropharynx: II-IV
• Nasopharynx: II-IV
• Hypopharynx: II-IV
• Larynx: II-IV
• Thyroid: VI

Indications

A neck dissection is generally indicated for any clinically positive nodal disease or advanced tumor stage in node-negative disease (T3-T4). 

Radical neck dissection is reserved only for clinically positive resectable neck disease involving the SCM, IJV, and CN XI.

Selective neck dissection and modified radical neck dissection (MRND) are the gold standard for clinically positive, resectable neck disease. Selective neck dissection is frequently performed for clinically and radiographically node-negative disease with a high T-stage (T3-T4). 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.[5] F

or a neck dissection to fall into the MRND 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 type III MRND CN XI, the IJV and the SCM are all spared.[12]

Contraindications

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. There is no definitive evidence to suggest this improves survival, but it is occasionally performed if the risk of a carotid blowout is felt to be high.[13]

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 patient's overall health due to underlying comorbidities and the inherent stressors of surgery.[14][15]

Equipment

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:

• 15 blade scalpels
•  Monopolar cautery with the protected tip
•  Bipolar bayonet forceps
•  Surgical laparotomy sponges
•  Sterile saline for irrigation
•  Suction
•  Elastic stays
•  Various retractors (Army-Navy, Langenbeck, etc.)
•  Various pickups (Addson, Gerald, Cushing, DeBakey, etc.)
•  Small and medium surgical clips
•  Right angle clamp
•  Double-prong skin hooks
•  Nerve hook
•  Fine-tipped and regular hemostats or Schnidt tonsil clamps
•  McCabe dissector
•  Allis clamps
•  Scissors (Jamieson tenotomy or Metzenbaum)
•  Sutures for vessel ligation (both regular and stick tie), such as 2-0 silk
•  Suture and/or staples for closure

Personnel

At a minimum, the surgical team should include an anesthetist, a circulating nurse, a surgical technologist, and the operating surgeon. If available, a surgical assistant is recommended.

Preparation

All patients should undergo routine preoperative evaluation by an anesthesia provider.  Patients with a concerning cardiac or complex medical history should receive preoperative medical clearance.  Any patient on anti-coagulation needs to have a clear plan for managing this medication perioperatively. 

If there is a concern for significant airway obstruction due to disease, anatomy, or pre-existing treatment (i.e., previous radiation or cervical spine surgery), awake fiberoptic intubation or awake tracheostomy may need to be planned and coordinated with the anesthesia team. 

All patients should have a complete oncologic workup completed prior to surgery.  This should include a biopsy with a diagnosis of cancer, imaging of the head and neck, and PET-CT or chest CT to evaluate distant metastasis and accurately stage the disease. 

Technique or Treatment

Patient positioning: The patient should be positioned supine, with the bed rotated, to allow full access to the patient's head and neck from both sides of the bed. A shoulder role may be used to extend the neck. Care is necessary to ensure that the head does not "hang" and is supported to prevent neck injury. 

Radical Neck Dissection 

Various incisions can be used, but the most common include the "hockey stick" incision from the mastoid tip extending inferiorly and then curving anteriorly into a midline neck crease at least two fingerbreadths below the mandible. A vertical line can be dropped from this incision inferiorly to create a "Y" incision to improve access inferiorly and posteriorly if needed. Many surgeons prefer to avoid this as it places a relatively hypo-perfused tri-point directly atop the carotid vessels after closure. Alternatively, the MacFee (parallel horizontal incisions), Schobinger, and reverse hockey stick incisions may be used per surgeon preference.[16]

Skin flaps are raised in the subplatysmal plane from the mandible down to the clavicle. Anteriorly, flaps should be raised to the lateral border of the strap muscles. Care should be taken to avoid communication with a tracheostomy if one has been placed. Posteriorly, the skin flaps should be raised to the anterior border of the trapezius. The skin flaps are then retracted using sutures or elastic stays.

The anterior border of the SCM is identified, and the muscle is retracted posteriorly while dividing the fascia that ensheaths the muscle. The carotid sheath is identified deep to the muscle. The  IJV will be identified as superficial and lateral to the carotid. The sternal and clavicular heads of the SCM are then divided. The omohyoid muscle, which lies just superficial to the IJV, is also divided.

With proximal and distal control of the IVJ, the inferior end of the internal jugular is isolated and ligated, ensuring that neither the carotid nor the vagal nerve (CN X) is included in the ligation. The thoracic duct generally enters the IJV at the junction of the IJV and subclavian vein on the left side. If the thoracic duct is violated, clips or sutures should be used to prevent a persistent chyle leak. The SCM and IJ are then reflected superiorly, allowing access to the supraclavicular lymph nodes and the floor of the neck (composed of the splenius capitus, levator scapulae, and scalene muscles). The adipose tissue and lymph nodes are then elevated off of the floor of the neck between the trapezius (posteriorly) and the lateral edge of the strap muscles (anteriorly). The deep layer of deep cervical fascia overlying the anterior scalene muscle is left intact to protect the phrenic nerve. The brachial plexus may be identified in the lateral, inferior portion of this dissection between the anterior and middle scalenes and should be protected.

The SCM, IJV, and lymph nodes are then rolled superiorly to the level of the hyoid bone. It will be necessary to ligate numerous branches of the IJ to accomplish this elevation. Medially, the cervical rootlets provide the appropriate depth of dissection (superficial to the deep layer of the deep cervical fascia). The rootlets are divided to allow the removal of all nodal contents from level V to be reflected anteriorly. Once deep to the cervical rootles, care must be taken to avoid injury to the phrenic nerve and brachial plexus. At this time, the surgeon may choose to save the root of CN XI and the trapezius branch. The CN XI branch to the SCM is sectioned, allowing further reflection of the SCM.

Next, the tendons of the digastric and stylohyoid muscles are divided while protecting the hypoglossal nerve (CN XII), allowing for access to the superior aspect of the IJV and the submandibular region contents. The facial artery and vein are ligated on the inferior aspect of the submandibular gland. The submandibular gland and associated lymph nodes are then reflected superiorly and raised off of the mylohyoid. The mylohyoid is retracted anteriorly to reveal the course of CN XII along with the lingual nerve and submandibular duct. The duct and submandibular ganglion are then ligated, preserving the lingual nerve. The facial vessels will again be encountered on the anterior aspect of the submandibular gland and require a second ligation. The submandibular gland is then dissected free from the mandible and reflected posteriorly, exposing the superior aspect of the IJV. The IJV is then ligated high in the neck.  

Dissection continues through the inferior 1/3 of the parotid--or parotid tail-- being careful to avoid injury to the main trunk of the facial nerve. Dissection then continues through the superior aspect of the SCM at the mastoid tip, allowing for en bloc removal of the specimen. The procedure may also be altered to elevate the parotid gland prior to ligation of the SCM, which may protect some branches of the lower division of the facial nerve.

The neck is then irrigated, and surgical drains are placed. The wound is closed in layers, which include the platysma, dermis, and skin.

Modified Radical Neck Dissection

The modified radical neck dissection uses the same incisions and elevation of subplatysmal flaps as the radical neck dissection.  

The dissection begins with an incision of the fascia over the SCM and medial dissection in the superior third of the SCM to identify CN XI. The nerve is then skeletonized superiorly to the posterior belly of the digastric muscle and posteriorly to the trapezius. After skeletonization of the anterior border of the trapezius muscle, the fat and lymph nodes of level V are elevated and rolled medially. Cervical rootlets are often preserved, though they can also be divided while preserving the deep layer of the deep cervical fascia overlying the levator scapulae and scalene musculature to protect the phrenic nerve and brachial plexus.[17] The nodal packet is then passed under the SCM.

The SCM is then retracted posteriorly, allowing access to levels II-IV of the neck. In level IIb of the neck, the lymphatic packet is dissected free from the deep layer of the deep cervical fascia and passed under CN. The nodal contents of level V are reflected medially and included with the nodes of levels II-IV. This tissue is reflected up to the carotid sheath. The nodal packet is divided inferiorly at the level of the clavicle after mobilization of the omohyoid inferiorly. Care should be taken to ligate the thoracic duct if encountered in this area. The transverse cervical artery will also be present in this area and should be avoided. 

The nodal contents are sharply divided free from the carotid sheath. Care is taken to avoid injury to the vagus nerve during the dissection. The ansa cervicalis is seen running across the IJV at this point of the dissection and may be sacrificed. Numerous IJV branches leaving anteriorly may need to be ligated during this step. The nodal tissue is elevated up to the level of the hyoid. 

Attention is then turned to the contralateral anterior digastric. The muscle is skeletonized from the mandible to the hyoid, and the level IA contents are rolled towards the ipsilateral anterior digastric. The ipsilateral digastric is then skeletonized to the digastric tendon and back along the posterior digastric tendon until the facial vein is reached. The facial vein is ligated, and the remaining posterior digastric muscle is skeletonized. 

Next, the marginal mandibular nerve is identified and protected by elevating the fascia overlying the submandibular gland. The level IB contents are then dissected free from the mandible and mylohyoid. Just deep to the digastric tendon, CN XII is identified and protected. At the posterior border of the submandibular gland, the facial artery is identified and may be ligated or traced through the submandibular gland and left intact. Next, the submandibular gland is retracted inferiorly, exposing the lingual nerve and submandibular duct. The submandibular duct and ganglion are ligated, protecting the lingual and hypoglossal nerves. Level IB is then dissected free from the mandible and reflected inferiorly.

Finally, the nodal packet is dissected free from the bifurcation of the IJV and common facial vein, allowing for en bloc removal of levels I-V. 

The surgical bed is irrigated with saline, inspected for hemostasis and chyle, and surgical drains are placed. The wound is then closed in layers.

Complications

Intraoperative complications include hemorrhage from major vessels, chyle fistula, pneumothorax, and damage to multiple nerves (particularly CN VII, CN X-XII, sympathetic chain, the brachial plexus, phrenic nerve, and lingual nerve). The spinal accessory nerve is commonly at risk, with a reported injury rate of 33% in modified radical neck dissections (and intentionally sacrificed in radical neck dissection) in a recent meta-analysis.[18] The marginal mandibular branch is also commonly injured, with rates ranging from 5% to 12%.[18][19] 

Postoperatively, complications are uncommon. They include wound dehiscence, percutaneous or pharyngocutaneous fistula, infection, hematoma, sialocele, and chyle fistula.

Clinical Significance

While numerous modifications have been made to the originally described radical neck dissection to reduce morbidity, the procedure remains an oncologically sound procedure to remove the advanced cervical disease that involves the IJV, SCM, and CN XI. In less advanced disease, modified radical neck dissection, and some cases, selective neck dissection has replaced this procedure.

Enhancing Healthcare Team Outcomes

All members of the interprofessional treatment team should be familiar with head and neck cancer patients. 

The anesthesia team may have to control for significant variations in blood pressure secondary to the manipulation of the carotid bulb during surgery.[20]

For patients with complex medical comorbidities, the expertise of hospitalists is invaluable in ensuring patients' other health parameters are maximized both before and after surgery.

Nursing staff caring for head and neck patients should be familiar with common postoperative complications so they can be identified promptly. Additionally, front-line caregivers can provide important information on a patient's mental state, as depression and anxiety are commonly seen in head and neck cancer patients.[21]

Nutritionists may assist in ensuring that patients are given adequate nutrition to promote healing and prevent wound breakdown. Speech-language pathologists also play a crucial role in rehabilitating swallowing, which is frequently affected after surgery.[22] Physical rehabilitation is critical in improving patient quality of life and mobility, particularly shoulder function.[23]

The care of head and neck cancer patients requires a truly interprofessional effort with open lines of communication to maximize patient outcomes.