Introduction
The central compartment contains the first nodal basin for cancer originating in the thyroid and parathyroid and can be involved in cancers of the laryngotracheal complex. This space encompasses the prelaryngeal, pretracheal, and paratracheal lymph nodes, also known as the level VI lymph nodes, although superior mediastinal nodes and retro-esophageal nodes are often included and represent level VII. In cases of squamous cell cancer involving the central compartment viscera or parathyroid carcinoma, comprehensive central compartment lymph node dissection is routinely employed, often in combination with ipsilateral thyroidectomy. However, the central compartment lymph nodes are most commonly affected by the regional spread of thyroid cancers. Well-differentiated thyroid cancer (WDTC) will prove to have metastases in the central compartment in 20% to 50% of cases. In these cases, central compartment neck dissection is unquestionably indicated, given the strong relationship between loco-regional control and treatment of clinically positive central compartment disease. Subclinical micrometastases have been shown to be present in up to 90% of cases of thyroid cancer, presumably with less defined clinical significance when compared with macrometastases. There has been no survival benefit associated with prophylactic treatment of the central neck, with equivocal data on local control. Patients with known metastasis in the central compartment are more likely to experience recurrence than their counterparts. Prophylactic central compartment dissection with total thyroidectomy has shown increased rates of postoperative hypocalcemia when compared with total thyroidectomy alone. However, the use of prophylactic central compartment neck dissection results in improved local control and decreases the potential risk of morbidity of reoperative surgery. Additionally, the pathologic assessment of the central compartment lymph nodes may help in risk stratification for additional adjuvant treatment such as radioactive iodine (RAI).
The literature fails to offer definitive evidence advocating prophylactic treatment of the central compartment in the management of well-differentiated thyroid cancer (WDTC). The role of prophylactic central compartment neck dissection remains controversial, largely due to the lack of a large randomized prospective trial—the feasibility of which is questionable given the prohibitively large sample size it would require. Ultimately, comprehensive preoperative evaluation and appropriate risk assessment and anatomic knowledge are imperative for successful surgical treatment of the central neck. The presence of medullary thyroid carcinoma, with or without evidence of nodal involvement, is an indication for dissection of the lymph nodes in the central compartment.
Key Operative Learning Points
- 1.
Central compartment dissection is often a reoperative surgery and may require a different surgical strategy (lateral to medial).
- 2.
Identification and continued observation of the recurrent laryngeal nerve (RLN) is the best way to avoid injury to the nerve.
- 3.
Identify and lateralize the superior parathyroid glands with their blood supply.
- 4.
A low threshold for auto-transplantation of inferior parathyroid glands after pathologic verification
- 5.
Complications are more common with paratracheal dissection, especially hypocalcemia, vocal fold paralysis, and injury to the esophagus.
Preoperative Period
History
- 1.
History of present illness
- a.
Determine if this is primary or secondary disease. Central compartment dissection is often employed in the case of a loco-regional recurrence of thyroid cancer.
- 1)
Obtain operative and pathology reports from previous surgeries.
- 1)
- b.
Evaluate for pre-existing morbidity.
- 1)
chronic obstructive pulmonary disease (COPD) or cardiovascular disease
- 2)
History of gastric bypass or gastrointestinal absorption abnormality
- a)
May require calcium challenge if parathyroid hormone (PTH) is elevated to ensure gastric absorption
- a)
- 1)
- c.
Invasive symptoms: hemoptysis, skin fixation, or voice changes from vocal cord paralysis
- 1)
Fiberoptic laryngoscopy
- 2)
Advanced imaging
- 1)
- a.
- 2.
Risk factors for severe morbidity
- a.
Pre-existing vocal fold paralysis
- 1)
Contralateral deficit may result in tracheostomy
- 1)
- b.
History of previous neck surgery or radiation
- c.
Hemoptysis or cough
- 1)
May signify invasive component
- 2)
Require cross-sectional imaging
- 1)
- a.
- 3.
Past medical history
- a.
Well-differentiated thyroid cancer (WDTC)
- b.
Medullary thyroid carcinoma, multiple endocrine neoplasia (MEN)
- a.
Physical Examination
- 1.
Complete examination of the head and neck
- a.
Palpate thyroid bed and paratracheal regions.
- 1)
Note location of masses with, relation to swallowing, fixation to skin, or underlying structures.
- 1)
- b.
Palpate lateral neck for lymphadenopathy.
- c.
Listen for hoarseness, stridor.
- d.
Determine location of native anatomy.
- 1)
Low-lying larynx/cricoid
- 1)
- a.
- 2.
Direct or indirect laryngoscopy
- a.
Essential in detecting vocal cord paralysis
- b.
The voice may be normal despite a paralyzed vocal cord.
- a.
Diagnostic Studies
Laboratory Studies
- 1.
Thyroid stimulating hormone (TSH)
- a.
Verify that the patient is euthyroid.
- a.
- 2.
Thyroglobulin (Tg)/thyroglobulin antibody (Tg Ab)
- a.
Determine relative burden of disease, especially in reoperative cases.
- a.
- 3.
Calcitonin
- a.
Patient with a family history of medullary thyroid carcinoma or MEN-2, or biopsy shows medullary thyroid carcinoma
- a.
- 4.
Parathyroid hormone
Imaging
- 1.
High-resolution ultrasound (US)
- a.
Microcalcifications are associated with markedly increased risk of malignancy, while cystic and spongiform appearance may be associated with benign lesions.
- b.
Low-cost, no radiation, and reliable when performed by experienced clinicians
- c.
Low sensitivity of detecting lymphadenopathy in the central neck due to shadowing effect of the thyroid gland
- a.
- 2.
Computed tomography (CT) and magnetic resonance imaging (MRI)
- a.
Helpful for:
- 1)
Substernal extension
- 2)
Cervical and mediastinal lymphadenopathy
- 3)
Invasion of surrounding structures such as trachea and esophagus
- 4)
Metastasis to distant sites
- 1)
- b.
High sensitivity and specificity in detecting cervical lymphadenopathy, and less operator dependence, offers visualization of adjacent structures
- c.
Expensive, radiation exposure, and use of iodinated contrast may preclude the use of RAI for 1 to 3 months
- a.
- 3.
Radionuclide scanning
- a.
Useful for rising Tg with negative imaging
- a.
- 4.
positron emission topography (PET) imaging
- a.
Useful for RAI negative, Tg positive patients
- a.
Fine-Needle Aspiration
- 1.
Essential for reoperative surgery
- a.
Minimally invasive, safe, and cost-effective
- b.
Sensitivity 65% to 98%, specificity 72% to 100%
- c.
US guidance increases accuracy and success of fine needle aspiration (FNA).
- a.
- 2.
Suspicious cervical lymph nodes or masses should undergo FNA.
- 3.
When multiple nodules are present, the largest and/or most sonographically suspicious should be biopsied preferentially.
- a.
Multiple nodules may need to be biopsied to increase diagnostic yield.
- b.
Biopsies should direct surgical planning.
- a.
Molecular Biomarkers
- 1.
Newer studies introduced to increase accuracy of FNA and better characterize the risk of malignancy, especially in indeterminate cytology, Atypia of Undetermined Significance (AUS), and Follicular Lesion of Undetermined Significance (FLUS). These markers may:
- a.
Reduce unnecessary surgery for benign lesions
- b.
Reduce completion thyroidectomy by guiding initial use of total thyroidectomy
- c.
Provide prognostic information such as:
- a.
- 2.
BRAF, RAS, TIMP1, RET/PTC, Pax8-PPARγ, galectin-3, cytokeratin, microRNA, gene sequencing
- 3.
Uncertain evidence regarding efficacy and utility
Indications
- 1.
Differentiated thyroid cancer
- a.
Initial surgery
- 1)
BRAF positive disease
- 2)
Gross extrathyroidal extension
- 3)
Presence of suspicious paratracheal lymph node (LN)
- a)
Microcalcifications
- a)
- 4)
Initial presentation of well-differentiated thyroid carcinoma (WDTC) with lateral neck metastasis
- 1)
- b.
Contralateral thyroid nodule or distant metastasis
- c.
Multinodular goiter with radiation exposure to the head and neck
- d.
First-degree family members with thyroid cancer
- a.
- 2.
Medullary thyroid carcinoma
- a.
May require concomitant lateral neck dissection
- a.
- 3.
Parathyroid cancer
- a.
Ipsilateral thyroid lobectomy
- a.
Contraindications
Relative Contraindication
- 1.
Uncontrolled medical disease
- 2.
Pregnancy
- a.
May elect to postpone until postpartum
- b.
If substantial growth, surgery may be performed in second trimester to reduce risk of miscarriage.
- a.
- 3.
Significant distant metastasis unresponsive to suppression
- 4.
Contralateral vocal fold paralysis
Absolute Contraindications
- 1.
Unresectable mediastinal disease
- 2.
Intracranial metastasis
Preoperative Preparation
- 1.
Screen for comorbidities.
- 2.
Document vocal cord movement with indirect laryngoscopy prior to surgery.
- 3.
Ensure euthyroid state.
- 4.
Accurately map disease and surgical plan.
Operative Period
Anesthesia
- 1.
General anesthesia with endotracheal intubation
Positioning
- 1.
Supine
- a.
Shoulder roll to extend neck slightly and elevate laryngeal framework
- b.
Head placed in a donut to prevent rotation
- a.
- 2.
The bed can be shifted away or rotated 180 degrees from anesthesia to provide more surgical space.
- 3.
The back and head may be elevated 10 to 30 degrees to reduce venous congestion.
- 4.
Prepare neck and upper chest with povidone-iodine or chlorhexidine (entire chest if sternotomy anticipated).
- 5.
Arms tucked at the side with padding of elbows and heels
- 6.
Protect face and eyes.
Perioperative Antibiotic Prophylaxis
- 1.
Perioperative antibiotics are not necessary in clean thyroid surgery.
- a.
A single preincision intravenous dosing of antibiotic is administered.
- 1)
Cefazolin or clindamycin
- 1)
- a.
Monitoring
- 1.
Intraoperative laryngeal nerve monitoring (IONM) may be used.
- a.
Endotracheal tube with surface electrodes placed at the level of the vocal cords
- b.
Likely greater utility in reoperative setting than primary setting
- c.
Increased cost and setup time
- d.
Useful adjunct for identification of recurrent nerve, which may result in decreased operative time and surgeon comfort
- a.
Instruments and Equipment to Have Available
- 1.
Basic head and neck set
- 2.
Monopolar and bipolar cautery
- a.
Consider advanced energy such as ultrasonic technology if a thyroidectomy is planned.
- b.
Surgical clips should be available in room (unopened).
- a.
- 3.
Mahorner, Lone Star, or Weitlander self-retaining retractors may be helpful if an assistant is not available.
- 4.
Kittner/peanut sponges are helpful for blunt dissection, retracting, and protecting nerves or parathyroid tissue from the heat of electrocautery or ultrasonic technology.
- 5.
Babcock forceps are helpful in grasping and retracting thyroid tissue.
- 6.
McCabe dissector
- a.
Has curved, precise, nonlocking tips
- b.
Excellent for identifying and dissecting out the nerves
- a.
Key Anatomic Landmarks
- 1.
Trachea/cervical spine
- 2.
Vasculature
- a.
Arterial
- 1)
Superior thyroid artery: first branch of the external carotid artery (branch of the common carotid in 16%)
- 2)
Inferior thyroid artery: branch of the thyro-cervical trunk
- 3)
Thyroidea ima artery (in thyrothymic adipose tissue)
- a)
Branch of the innominate, subclavian, or right common carotid, internal thoracic arteries, or aortic arch
- b)
Supplies thyroid isthmus inferiorly
- c)
Present in 2% to 12% of cases
- a)
- 4)
Carotid artery system
- a)
Lateral border of central compartment
- a)
- 5)
Innominate artery
- a)
Inferior extent of dissection
- b)
Right common carotid artery may branch early
- a)
- 1)
- b.
Venous
- 1)
Innominate vein inferiorly
- 2)
Internal jugular system
- a)
Lateral border
- a)
- 1)
- c.
Lymphatics: prelaryngeal, pretracheal, paratracheal, parapharyngeal, deep cervical, and supraclavicular nodes
- a.
- 3.
RLN
- a.
Descends within the vagus nerve
- 1)
Left: wraps around the aortic arch below the ligamentum arteriosum and returns to the neck in the trachea-esophageal groove
- 2)
Right: branches from the vagus higher than the left and wraps around the subclavian artery before ascending along the tracheoesophageal groove more laterally than the left
- 3)
Courses beneath the inferior pharyngeal constrictor muscle and passes posterior to the cricothyroid joint
- 4)
Enters the larynx above the first tracheal ring, below the cricoid cartilage
- 1)
- b.
Landmarks
- 1)
Simon’s triangle: bound by common carotid artery laterally, esophagus medially, and inferior thyroid artery superiorly
- 2)
Variably associated with the inferior thyroid artery
- a)
Found behind or between branches of the artery in 80%
- b)
The relationship between the RLN and the inferior thyroid artery is different on the left and right in about 50% of cases.
- a)
- 3)
Usually in the vicinity of the inferior parathyroid gland
- 4)
Majority found within 3 mm of Berry’s ligament, often laterally, and sometimes passing through the ligament
- 5)
May pass through the capsule of the thyroid gland
- 6)
Deep to the tubercle of Zuckerkandl in 98% of patients
- 7)
Non-RLNs can be found in up to 0.7% of patients.
- a)
Primarily on the right (associated with aberrant subclavian artery), except in cases of situs inversus (dextrocardia)
- b)
May arise at the level of the thyroid cartilage or superior pole of thyroid and course directly into the larynx
- a)
- 8)
May divide at various levels, and 40% to 65% bifurcate or trifurcate—more than 5 mm below the cricoid cartilage
- 1)
- a.
- 4.
Superior laryngeal nerve (SLN)
- a.
Arises from the nodose (inferior) ganglion of the vagus nerve about 4 cm above the carotid bifurcation, near the jugular foramen
- 1)
Descends lateral to the pharynx and posteromedial to the carotid sheath
- 2)
Splits into internal and external branches about 2 cm above the superior pole of the thyroid, with the former penetrating through the postero-inferior thyrohyoid membrane
- 1)
- b.
Function
- 1)
Internal branch: sensation and secretomotor function to the supraglottis, epiglottis, base of the tongue, piriform sinus, and upper esophageal sphincter
- 2)
External branch: cricothyroid and inferior constrictor muscles
- 1)
- c.
SLN external branch landmarks
- 1)
Sternothyrolaryngeal triangle (Joll’s triangle): bound by the midline medially, superior thyroid pole laterally, and attachments of the strap muscles superiorly
- 2)
Deep to the superior thyroid artery 82% to 86% of the time and penetrates the inferior constrictor muscle at variable levels
- 3)
Can be found below, and up to 1 cm above, the level of the upper pole of the thyroid in 37% of patients
- 1)
- a.
- 5.
Parathyroid glands
- a.
Superior parathyroids
- 1)
Fourth branchial arch structure
- 2)
Superior or inferior thyroid vessels
- 3)
Frequently above cricoid cartilage
- 1)
- b.
Inferior parathyroids
- 1)
Third branchial arch structure
- 2)
Variable location
- a)
Frequently below cricoid cartilage
- a)
- 1)
- a.
Prerequisite Skills
- 1.
Intimate knowledge of the use of surgical instruments and meticulous soft tissue/neural dissection
Operative Risks
- 1.
RLN injury
- a.
Preferential visual identification of the RLN before the thyroid or lymph nodes are dissected off the trachea and esophagus
- a.
- 2.
SLN injury
- a.
Carefully dissect out the superior pole to ensure the SLN is not coursing within the vascular pedicle before ligation.
- b.
Avoid thermal injury or excessive dissection of cricothyroid and constrictor muscles.
- a.
- 3.
Parathyroid injury or devascularization
- a.
Lateralize parathyroids with their blood supply when medializing the thyroid gland.
- b.
Reimplant normal, frozen biopsy confirmed parathyroids.
- a.
- 4.
Intraoperative hemorrhage
- a.
Anterior jugular veins: Carefully undermine subplatysmal skin flaps and ligate large vessels.
- b.
Carotid artery: Use a blunt instrument when dissecting in this region, especially the superior pole, and be aware of depth of dissection at all times.
- c.
Thyroid gland and surface vessels: Use blunt dissection close to the thyroid capsule and meticulously seal or ligate the vasculature.
- a.
- 5.
Tracheoesophageal injury
- a.
Most commonly occurs at Berry’s ligament or subcricoid trachea
- b.
Primary repair is usually satisfactory.
- a.
Surgical Technique
- 1.
Marking
- a.
Mark a 5-to 6-cm horizontal incision line between the cricoid cartilage and suprasternal notch.
- 1)
Usually 2 to 3 cm above the sternal notch
- 1)
- b.
Use an existing neck crease or line of relaxed skin tension that could be lengthened if lateral neck dissection is ever needed.
- c.
Mark the incision higher in younger patients because the scar will migrate lower over time and a scar below the clavicle is unsightly.
- d.
If sternotomy is possible, the incision should be at the clavicles or lower.
- a.
- 2.
Local anesthesia
- a.
Inject 0.25% bupivicaine with 1:200,000 epinephrine 1 to 2 cm above and below the incision line to reduce distortion and maximize hemostasis in the incision.
- a.
- 3.
Incision
- a.
Use a #15 blade to incise the dermis to the platysma.
- b.
Incise through the platysma to the subcutaneous tissue with electrocautery to the investing fascia.
- c.
Avoid injuring the communicating anterior jugular veins.
- a.
- 4.
Elevate skin flaps
- a.
Using skin rakes for tension, subplatysmal flaps are elevated with blunt dissection and electrocautery in the plane just above the investing fascia and anterior jugular veins up to the thyroid notch and down to the sternal notch.
- b.
Ligate large vessels with 2-0 silk ties.
- c.
Protect the skin with occlusive material such as Steri-Strips (preferred by the senior author; Fig. 67.1 ).
- 1)
Suture in place with locking 2-0 silk running sutures.
- 2)
Protects the skin from heat or instrument injury
- 1)
- a.
