Classification of neck dissection

Introduction: Currently several types of cervical lymph node dissections are in vogue in the surgical management of head and neck malignancy. It is highly essential to adopt a common nomenclature for the nodal groups in the neck and the surgical procedures followed in their removal. The classification of neck dissections recommended by the American Academy of Otolaryngologists primarily takes into account the nodal groups of the neck that are removed and secondarily the anatomic structures that are preserved. Commonly preserved anatomical structures include the spinal accessory nerve and the internal jugular vein. When the various types of neck dissections are analyzed using the above point of view, three types of neck dissections can be described. They are radical and modified radical, selective and extended types. The newer classification evolved has managed to remove certain types of selective neck dissection thereby reducing the confusions involved.

It was also pointed out by the American Academy of Otolaryngologists in 2001, regardless of what name a neck dissection is given, the operative record should reflect accurately what was done during surgery in terms of the nodal groups that were removed and the important neural and vascular structures that were removed or preserved. The surgeon also must orient the surgical specimen for the pathologist and identify the different nodes groups it contains. This will help the pathologist in generating a meaningful report.

Classification of neck dissections:

Radical neck dissection:

This surgical procedure is defined as en bloc removal of lymph node bearing tissues of one side of the neck from the inferior border of the clavicle and from the lateral border of the strap muscles to the anterior border of trapezius muscle. Included in this specimen are the spinal accessory nerve, the internal jugular vein and the sternomastoid muscle.

It was Crile in 1906 who first described the procedure of systematic removal of lymphatics of the neck. He also firmly believed that removing the internal jugular vein was essential because of its intimate relationship to the lymph nodes of the neck. He preserved the spinal accessory and ansa hypoglossal nerves were preserved.

Martin in 1950 said that the concept of cervical lymphadenectomy for cancer was inadequate unless the entire node bearing tissues of one side of the neck was removed. He also believed that this was not possible unless the spinal accessory nerve, internal jugular vein and sternomastoid muscle are included in the specimen. He also said that normal lymphatic flow is interrupted by metastasis in a node, causing further tumor dissemination to occur in any direction and a less radical operation would disseminate and stimulate the growth of tumor mass.

Removal of sternomastoid muscle facilitates access to internal jugular vein and the removal of jugular chain of nodes.

Indication:

1. Radical neck dissection is indicated in patients with clinically obvious lymph node metastasis.

2. Large cervical nodal metastasis

3. Cervical metastasis involving multiple nodal areas of neck

4. Should be performed only in patients with malignant tumors of head and neck

Radical neck dissection is not indicated in patients with no palpable lymph nodes.

Modified radical neck dissection:

This category of neck dissection procedures includes the various modifications that have been incorporated into the procedure of radical neck dissection with the intention to reduce the morbidity by preserving one or more of the following structures: the spinal accessory nerve, internal jugular vein and sternomastoid muscle.

Three neck dissections have been included in this category. They differ from each other only in the number of neural, vascular and muscular structures that are preserved.

1. Modified radical neck dissection with preservation of spinal accessory nerve
2. Modified radical neck dissection with preservation of spinal accessory nerve and internal jugular vein
3. Modified radial neck dissection with preservation of spinal accessory nerve, internal jugular vein and sternomastoid muscle. This procedure also goes by the name functional neck dissection

Modified radical neck dissection with preservation of spinal accessory nerve:

This surgery involves en bloc removal off lymph node bearing tissues of one side of the neck from the inferior border of the mandible to the clavicle and from the lateral border of strap muscles to the anterior border of trapezius. The spinal accessory nerve is preserved. The internal jugular vein and sternomastoid muscle is included in the specimen.

Advantages:

1. Preservation of spinal accessory nerve prevents frozen shoulder development
2. Causes less cosmetic deformity even when performed bilaterally
3. It has been shown that spinal accessory nerve in majority of cases is not in proximity to the grossly involved nodes and hence its preservation does not compromise the oncologic soundness of the surgery

Indications:

1. Used in surgical treatment of neck in patients with clinically obvious nodal metastasis

2. In patients with multiple nodal involvement in various nodal levels

3. Spinal accessory nerve should not lie close to the involved node

Modified radical neck dissection with preservation of spinal accessory nerve and internal jugular vein:

This surgery involves the dissection of node bearing tissues of one side of the neck en bloc preserving the spinal accessory nerve and the internal jugular vein. Usually this procedure is decided on the table when during the course off neck dissection the Metastatic tumor in thee neck is found to be adherent to the sternomastoid muscle but away from the accessory nerve and the internal jugular vein. This scenario occurs occasionally in patients with hypopharyngeal / laryngeal tumors with metastasis under the middle third of sternomastoid muscle.

Modified radical neck dissection with preservation of spinal accessory nerve, internal jugular vein and sternomastoid muscle:

This surgery involves en bloc removal of lymph node bearing tissues of one side of neck, including lymph node levels I – V preserving the spinal accessory nerve, internal jugular vein and sternomastoid muscle. It should be borne in mind that the muscular and vascular aponeurosis of the neck delimits compartments filled with fibroadipose tissue. The lymphatic system of the neck contained within these compartments can be excised in an anatomic block by stripping the fascia off muscles and vessels. Except the vagus nerve which runs within the carotid sheath, the nerves of the neck don’t follow the aponeurotic compartment distribution. The phrenic nerve and brachial plexus are partially within a compartment. The hypoglossal and spinal accessory nerves run across compartments. Unless these nerves are directly involved by tumor, they can be dissected free and preserved.

Indications:

1. This surgery is the treatment of choice even in N0 neck patients with squamous cell carcinoma of the upper aero digestive tract, especially when the primary is in the larynx or Hypopharynx. The nodes of submandibular triangle are at low risk in these patients and hence need not be removed.
2. This surgery is indicated in the treatment of N1 neck when the Metastatic nodes are mobile and are no greater than 2.5 – 3 cms.
3. This surgery is indicated in patients with well differentiated carcinoma of thyroid who have palpable nodal metastasis in the posterior triangle of neck.

Selective neck dissection:

This involves removal of only the nodal groups that carry the highest risk of containing metastasis according to the location of the primary, preserving the spinal accessory, internal jugular vein and sternomastoid muscle. This procedure was popularized in 1960’s by surgeons at The University of Texas Anderson Cancer Centre.

Justification for this procedure:

1. This procedure preserves the functional and cosmetically relevant structures.
2. This procedure is also anatomically justified. Studies have demonstrated that cervical metastasis occur in predictable patterns in patients with squamous cell carcinomas of head and neck.
3. Nodal groups frequently involved in patients with carcinomas of oral cavity are the jugulodigastric and midjugular group of nodes.
4. Nodes of submandibular triangle are frequently involved in patients with carcinoma of the floor of mouth, anterior tongue and buccal mucosa. These tumors can metastasize to both sides of the neck.
5. Tumors of oral cavity metastasized most frequently to the neck nodes in levels I, II, and III, whereas carcinomas of oropharynx, Hypopharynx and larynx involved mainly thee nodes in the levels II, III and IV.
6. Selective neck dissection provides the surgeon with some staging information.
7. This procedure can be used for the elective treatment of regional lymphatics with excellent survival rates.

There are four selective neck dissections described:

Selective neck dissection of level I – III: This is also known as Supraomohyoid neck dissection. If the selective dissection covers even level IV nodes then it is known as “Extended Supraomohyoid neck dissection”. The nodes removed are those contained in the submental and submandibular triangles (level I), Upper jugular region (level II), the midjugular level (level III). The posterior limit of dissection is marked by the cutaneous branches of cervical plexus and the posterior border of sternomastoid muscle. The inferior limit is the omohyoid muscle as it crosses the internal jugular vein.

Indications:

1. This procedure is commonly used in the management of neck in patients with oropharyngeal malignancies.
2. In patients with midline oropharyngeal tumors then bilateral neck dissection should be carried out as nodes of both sides are at risk in these patients.

Selective neck dissection levels II – IV: This dissection is also known as “lateral neck dissection”. It involves removal of the upper (level II), middle (level III) and lower (level IV) jugular groups of nodes. The superior limit of dissection is the digastric muscle and the mastoid tip. The inferior limit is the clavicle. The antero medial limit is the lateral border of sternohyoid muscle. The posterior limit of dissection is marked by the cutaneous branches of cervical plexus and the posterior border of sternomastoid muscle.

Indications:

1. This procedure in indicated in the treatment of neck in patients with squamous cell carcinoma of the larynx, oropharynx and Hypopharynx.

2. For tumors of the supraglottis and posterior pharyngeal wall the dissection is often bilateral.

Selective neck dissection level VI: This procedure is also known as anterior neck dissection or central compartment dissection. This procedure involves removal of prelaryngeal, pretracheal as well as paratracheal nodes on both sides.

Indication:

1. This procedure is used to treat patients with cancer of midline structures of the anterior inferior aspect of the neck and thoracic inlet.
2. Cancers involving thyroid gland
3. Cancers involving glottic / subglottic regions of larynx

Selective neck dissection for cutaneous malignancies of the head and neck:

The extent of regional node dissection in patients with cutaneous malignancies depends on the location of the primary lesion and the nodal groups that are likely to harbor metastasis. This is described separately because of the extensive lymphatic drainage that is possible. In these patients the parotid, facial, and external jugular groups will have to be addressed along with the classical neck node dissection.

Extended neck dissections:

This surgical procedure includes removal of any lymph node groups / structures that are not routinely removed in neck dissection. This could be skin of neck, carotid artery, levator scapulae muscle, vagus, hypoglossal nerves. Nodal structures could be retropharyngeal, paratracheal and upper mediastinal.

Problems with neck dissection:

1. In radical neck dissection procedures the spinal accessory nerve is removed. This causes denervation of the trapezius muscle. This muscle is one of the most important shoulder abductors. This destabilizes the scapula causing it to flare. The patient will not be able to abduct the shoulder above 90 degrees. The classic feature is the shoulder syndrome characterized by pain, weakness and deformity of shoulder girdle. The shoulder dysfunction is not only due to dysfunction of spinal accessory nerve, but also can occur secondary to glenohumeral stiffness caused by weakness of the scapulo humeral girdle muscles and post operative immobility.
2. Cosmetic neck deformity
3. Infection
4. Air leaks – This can cause flap necrosis. When these leaks are associated with tracheal wound it is sinister. Suction drain should be inserted to prevent this complication
5. Bleeding
6. Chylous fistula
7. Facial / cerebral oedema – due to ligation of internal jugular vein. This is more pronounced when internal jugular veins on both sides are ligated.
8. Blindness – very rare. Occurs after bilateral radical neck dissection. Possible causes include intraoperative hypotension associated with severe venous distention. Bilateral occipital lobe infarcts have also been implicated as possible factors
9. Apnea – Some patients become apnoeic due to loss / diminished ventilatory responses due to carotid body denervation after bilateral neck dissection.
10. Jugular vein thrombosis
11. Jugular vein blow out – Common in patients following post operative radiotherapy