Indications for the performance of a central neck dissection (CND) for cancer of the thyroid can be confusing. The reason for this is the lack of good evidence-based data on its utility when performed routinely in the management of differentiated cancer of the thyroid. When reading the pertinent literature, it becomes obvious that one of the limitations is that there is no standardization of the operation. Boundaries and compartments are not well defined, and the reports often fail to report whether these procedures were being performed in the presence or absence of gross lymph node metastasis. These shortcomings prompted the convergence of a subgroup of experts on cancer of the thyroid to come together under the auspices of the American Thyroid Association (ATA) to formulate a consensus statement on the anatomy and terminology pertinent to CND. The group concluded that the CND should consist of level VI and level VII lymph node basins and must contain the prelaryngeal (delphian), pretracheal, and at least one paratracheal nodal basin. The surgery should be designated as elective or therapeutic. Obvious lymph node metastasis in the central neck should be treated with therapeutic intent accomplished by a compartmental dissection. While elective CND for medullary thyroid cancer is advocated, controversy exists in differentiated thyroid cancer. This chapter describes the technical performance of a CND and considerations for when it should be performed.

A patient is nearly always diagnosed with a primary cancer of the thyroid prior to making a determination of whether a CND needs to be performed. The entire neck should be palpated. A firm, fixed thyroid cancer with suspected extrathyroidal spread warrants a CND. Flexible fiberoptic laryngoscopic examination of the vocal folds should be conducted in all patients undergoing thyroid surgery. Vocal fold paralysis, lateral neck lymphadenopathy confirmed as cancer by fine needle aspiration (FNA), central neck lymphadenopathy confirmed on physical examination, radiographic imaging or intraoperative inspection, medullary cancer of the thyroid, and suspicion of more aggressive variants of thyroid cancer are all accepted indications for CND. This is
in accordance with the ATA guidelines. A patient who has previously undergone a total thyroidectomy with or without radioactive iodine (RAI) may have an increasing serum thyroglobulin level determined as part of follow-up surveillance. Radiographic imaging (US, computed tomography [CT], MRI, positron emission tomography [PET]) is usually instituted. If a central mass in the neck is found during the surveillance period, a determination as to whether an FNAB should be carried out is made as a multidisciplinary team and usually only if surgery is considered beneficial.

The issues of CND should be discussed with the patient when the procedure is being considered. The CND may be performed electively or therapeutically at the time of thyroidectomy or therapeutically in a reoperative setting. The literature suggests the patient may be at an increased risk of complications compared to total thyroidectomy alone. US evaluation of the central neck is helpful to appreciate the extent of lymph node metastasis as it relates to important structures in the central compartment and is also helpful to confirm recurrent/persistent thyroid cancer by US- or CT-guided FNA. Axial imaging (CT, MRI, and PET-CT) may be helpful in determining the degree of involvement of associated central structures in the neck such as the laryngotracheal complex, esophagus, and carotid artery. Administration of iodinated contrast with CT may preclude early postoperative RAI administration. This usually is not a problem in the setting of recurrent cancer of the thyroid where the tumors are typically non-RAI avid.

The borders of the central compartment for central neck dissection are: superior-horizontal line at the inferior border of the cricoid and the RLN insertion point, inferior plane on level with innominate artery, lateral-common carotid artery, posterior-prevertebral fascia, anterior: sternothyroid muscle, medial border for unilateral central compartment dissection-medial edge of contralateral strap muscles (Figure 19.1).

I will divide the central neck dissection into two categories: Primary or reoperative to emphasize some differences in the techniques.