The various functions and levels of lymph nodes are summarized in a previous A & P section under the heading of lymph node biopsy . The different levels are critical to the understanding of the different types of Neck Dissection.
The lymphatics are referred to according to their position in the Head and Neck region.
Level I – Submental and submandibular
Level II – Upper deep cervical
Level III – Mid deep cervical
Level IV – Lower deep cervical
Level V – Posterior triangle
Level VI – Paratracheal
Level VII – Superior mediastinal
Lymph nodes in the Head and Neck region are typically the first route of spread of malignant disease in the upper aerodigestive tract. If this happens then the lymph nodes are sometimes considered for surgical removal. This is referred to as a ‘Neck Dissection’. Occasionally even if the neck has no clinically or radiologically proven neck nodes and the risk is high a Neck Dissection may be undertaken to stage the neck.
The degree and seriousness of lymph node spread in Head and Neck Squamous Cell Cancers is graded according to N staging in the TNM staging system.
N1 Single ipsilateral lymph node <3cm
N2a Single ipsilateral lymph node 3-6cm
N2b Multiple ipsilateral lymph nodes <6 cm
N2c Contralateral lymph node
N3 Lymph node >6cm
There are many types of neck dissection that are described. Simply put they can be ordered into the following list.
Radical Neck Dissection Levels I-V dissected sacrificing Internal jugular vein(IJV), Accesory nerve and Sternocleidomastoid muscle (SCM)
Modified Radical Neck dissection Levels I-V dissected preserving any of the named three structures above (IJV, accessory nerve or SCM)
Extended Radical Neck Dissection Levels I-V dissected including any other lymph node levels
There are a variety of selective neck dissections depending on the site of the primary removing different lymph nodal groups that are likely to drain from the primary.
Surgery can be performed through a variety of skin incisions all of which will leave a scar. Clearly there is always a risk of bleeding and the great vessels (IJV and carotid artery) are in the territory of most neck dissections.
Very importantly there are nerves in the territory of the dissection that sometimes have to be sacrificed. These typically are:
The Accessory nerve:
If injured causes stiffness in the shoulder and some decrease in range of movement.
The Hypoglossal nerve:
If injured causes restriction of movement of that side of the tongue.
The Phrenic nerve:
This nerve supplies the diaphragm movement and is unusual to be injured.
Marginal mandibular nerve:
This is a branch of the facial nerve and is often seen and preserved in the dissection.
Rarely other channels that convey fatty acids from the gut to the venous system can be injured with a neck dissection. This is unusual but can cause problems in the postoperative period.
Most patients will have a drain placed post-operatively which is removed when it’s output decreases significantly. A patient can expect to stay in hospital from 2-5 days after the operation, however this is in the ideal case.