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Chyle is a milky fluid consisting of lymph / interstitial fluid and emulsified fats. The largest conduit of it is in the thoracic duct that starts in the abdomen ascend to the neck and enters the venous system at the junction of the internal jugular vein and the subclavian vein.

A chyle leak can occur at the time of a neck dissection clearing lymph nodes from the territory where the thoracic duct enters the venous system. A chyle leak has been incurred by every regularly practicing surgeon who undertakes neck dissection. More often than not it occurs when large nodes have to be cleared from the root of the neck where the duct is.

It can lead to a profuse loss of this milky fluid which is protein rich and patients can therefore become fluid depleted and malnourished rapidly with a high output fistula. Special feeds can be instituted to decrease output, pressure can also help decrease output. Surgical exploration can sometimes localise the leak. Occasionally thoracoscopic ligation of the duct in the chest can be undertaken.

This is a serious condition and is best avoided and when incurred should be carefully managed from a surgical and dietetic perspective.

A thyroglossal cyst is a benign cyst typically, that is a remnant left behind when the thyroid gland is formed in utero. It is a remnant of the descending tract that is associated with the thyroid gland as it descends in the neck to its normal position.

Typically these cysts present in the first few decades of life with an increase in size. they can become infected where they become enlarged and painful. These cysts require a careful clinical examination followed by an ultrasound related to the cyst itself but also the thyroid gland as occasionally all the thyroid tissue of the patient may be situated in this cyst.

If troublesome it is appropriate to remove the cyst, however it should b undertaken by someone who has experience in performing the operation as there is a high recurrence rate if the operation is not performed correctly. The central portion of the hyoid bone should be removed as part of the operation as during development the descending tract is intimately associated with the hyoid bone and to remove all the tract therefore, requires the removal of this portion of the hyoid bone. The operation is referred to as a Sistrunks procedure, however some people refer to it as an anterior neck dissection as this term covers a wider resection associated with a decreased incidence of recurrence.

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

Neck Dissection

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.

COMPREHENSIVE

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

SELECTIVE

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.