Overview
Definition:
Level VI central compartment neck dissection is a surgical procedure that involves the systematic removal of lymph nodes and surrounding tissues located in the anterior midline of the neck, specifically between the anterior and posterior bellies of the digastric muscles, superiorly
the clavicle, inferiorly
and the anterior border of the sternocleidomastoid muscles, laterally
This compartment primarily contains the thyroid gland, parathyroid glands, prelaryngeal (Delphian) lymph nodes, strap muscles, and the recurrent laryngeal nerves.
Epidemiology:
This dissection is most commonly performed in the context of thyroid carcinoma (papillary, follicular, medullary, anaplastic) to remove central nodal metastases
It is also indicated for certain parathyroid pathologies requiring gland or lymph node excision and occasionally for metastatic squamous cell carcinoma from head and neck primaries involving the central nodes.
Clinical Significance:
Accurate and complete Level VI dissection is crucial for accurate staging and effective treatment of thyroid malignancies and selected other head and neck cancers
It allows for radical clearance of potentially involved nodal basins, influencing adjuvant therapy decisions, prognosis, and preventing local recurrence
Understanding the anatomical boundaries and critical structures within this compartment is paramount to minimize operative morbidity, particularly recurrent laryngeal nerve injury and hypoparathyroidism.
Indications
Thyroid Cancer:
Clinically evident or radiologically suspected lymph node metastasis in the central compartment
Papillary thyroid carcinoma with extrathyroidal extension, multifocal disease, or aggressive subtypes
Medullary thyroid carcinoma with evidence of C-cell hyperplasia or metastatic disease
Anaplastic thyroid carcinoma if amenable to surgery.
Parathyroid Pathology:
Parathyroid carcinoma
Ectopic parathyroid adenoma with suspected nodal involvement
Large parathyroid adenomas requiring extensive dissection.
Other Malignancies:
Metastatic squamous cell carcinoma from oral cavity, pharynx, or larynx with central nodal involvement
Lymphoma involving central neck nodes.
Contraindications:
Distant metastatic disease precluding curative intent
Severe comorbidities rendering the patient unfit for major surgery
Unresectable disease based on imaging.
Preoperative Preparation
History And Physical:
Detailed history including voice changes, dysphagia, dyspnea, neck mass characteristics
Physical examination to assess thyroid gland, cervical lymphadenopathy, vocal cord function (laryngoscopy if indicated), and signs of hypocalcemia.
Imaging:
Ultrasound of the neck for thyroid nodules and cervical lymph node assessment
CT scan with contrast to delineate extent of disease, relationship to vital structures, and assess extrathyroidal extension
Radioiodine scans (RAIU) for differentiated thyroid cancers to assess uptake by primary tumor and metastases
MRI for specific anatomical detail if needed.
Laboratory Tests:
Thyroid function tests (TSH, FT4, FT3, TPO antibodies, thyroglobulin)
Serum calcium, phosphate, and parathyroid hormone (PTH) levels
Calcitonin for suspected medullary thyroid carcinoma
Complete blood count (CBC), coagulation profile, electrolytes, renal and liver function tests.
Patient Counseling:
Informed consent regarding the procedure, potential risks (recurrent laryngeal nerve injury, hypoparathyroidism, chylous leak, infection, bleeding), expected outcomes, and alternative treatment options
Discussion on the importance of calcium and Vitamin D supplementation postoperatively.
Procedure Steps
Anesthesia And Positioning:
General anesthesia with endotracheal intubation
Supine position with neck extended, head slightly turned contralaterally
Mayfield headrest may be used.
Incision:
Typically a transverse cervical incision (e.g., in a skin crease) at the level of the cricoid cartilage, extending laterally
A bilateral subplatysmal flap is raised superiorly and inferiorly to expose the strap muscles and anterior neck structures.
Exposure Of Compartment:
Midline division of strap muscles (sternohyoid, sternothyroid) to expose the thyroid gland and surrounding lymph nodes
Identification and careful preservation of the cricothyroid artery and vein
Identification of the medial border of the sternocleidomastoid muscle.
Dissection And Node Excision:
Systematic en bloc resection of lymphatic tissue and associated structures from the superior aspect (below hyoid bone/cricothyroid membrane) to the inferior aspect (above clavicle/innominate artery)
Meticulous dissection is performed laterally to the anterior border of the sternocleidomastoid muscles
Careful identification and preservation of the recurrent laryngeal nerve(s) and parathyroid glands are paramount
Identification of pretracheal and paratracheal nodes.
Management Of Critical Structures:
Recurrent laryngeal nerves: Visualized and preserved bilaterally
If tumor involvement is suspected or nerve injury occurs, ligation or resection may be necessary, documented carefully
Parathyroid glands: Identified, preserved in situ if normal and viable, or harvested for autotransplantation into the sternocleidomastoid muscle if devascularized or removed
Arterial supply to parathyroids from the inferior thyroid artery is often divided, necessitating careful management.
Hemostasis And Drainage:
Meticulous hemostasis achieved using electrocautery, bipolar forceps, and ligatures
Placement of surgical drains (e.g., Jackson-Pratt) to monitor for bleeding, chyle, or seroma formation.
Closure:
Reapproximation of strap muscles if divided
Subcutaneous closure followed by skin closure, often with absorbable sutures or staples.
Postoperative Care
Monitoring:
Close monitoring of vital signs, airway patency, and signs of respiratory distress
Serial assessment for recurrent laryngeal nerve injury (voice quality, swallowing).
Calcium Monitoring:
Frequent serum calcium and PTH levels (e.g., 6-12 hours postoperatively and daily thereafter)
Monitoring for symptoms of hypocalcemia (paresthesias, tetany, Chvostek’s/Trousseau’s signs).
Pain Management:
Adequate analgesia, typically with intravenous or oral opioids and non-opioid analgesics.
Drain Management:
Monitoring of drain output for volume, color, and character
Drains usually removed when output is less than 20-30 ml per 24 hours.
Dietary Considerations:
Advancement of diet as tolerated
Adequate fluid intake
Calcium and Vitamin D supplementation, especially if hypoparathyroidism is suspected or confirmed.
Vocal Cord Assessment:
Postoperative laryngoscopy may be performed if there is significant concern for recurrent laryngeal nerve injury or to establish baseline vocal cord function.
Complications
Early Complications:
Recurrent laryngeal nerve injury (temporary or permanent vocal cord paralysis)
Hypoparathyroidism (temporary or permanent hypocalcemia)
Hematoma or seroma formation
Wound infection
Chylous leak (rare but significant)
Phrenic nerve injury (rare).
Late Complications:
Permanent hypocalcemia requiring lifelong treatment
Recurrence of disease
Scarring and cosmetic deformity
Chronic dysphagia or aspiration
Persistent hoarseness.
Prevention Strategies:
Meticulous surgical technique with clear visualization of vital structures
Experienced surgical team
Careful identification and preservation of recurrent laryngeal nerves and parathyroid glands
Prophylactic autotransplantation of parathyroid glands if devascularized
Careful hemostasis
Prompt drain removal
Appropriate antibiotic prophylaxis if indicated.
Key Points
Exam Focus:
The anatomical boundaries of Level VI are critical: between the hyoid bone and clavicle, and bounded laterally by the anterior borders of the sternocleidomastoid muscles
Key structures include the thyroid gland, parathyroid glands, prelaryngeal lymph nodes, strap muscles, and recurrent laryngeal nerves.
Clinical Pearls:
Always identify the recurrent laryngeal nerve before dissecting near it
If parathyroid glands are devascularized, harvest them for autotransplantation into the sternocleidomastoid muscle
Prelaryngeal (Delphian) lymph nodes are a common site for thyroid cancer metastasis and should be meticulously removed
Consider prophylactic central dissection for aggressive thyroid cancers even without palpable nodes.
Common Mistakes:
Failure to identify or preserve recurrent laryngeal nerves, leading to vocal cord paralysis
Accidental removal or devascularization of parathyroid glands leading to severe hypocalcemia
Inadequate dissection, leaving behind involved lymph nodes, leading to treatment failure
Extension of dissection too laterally, violating oncologic principles for central neck dissection.