Introduction
Although thyroid disease has been recognized for centuries, consistently accepted techniques of thyroid surgery date back approximately 100 years. With a combined mortality of 40% from hemorrhage and sepsis, thyroidectomy was banned by the French Academy of Medicine in 1850. However, with the advent of antiseptic technique, vascular ligation, and precise capsular dissection, Theodor Kocher reduced the perioperative mortality rate to less than 1% in 900 cases for benign goiter in 1895. He was awarded the Nobel Prize in Medicine in 1909 for his contributions to thyroid surgery. Crile, Lahey, and the Mayo brothers founded their internationally famous private clinics largely based on their ability to perform thyroid surgery safely.
Thyroid nodules are found by palpation in 4% to 7% of subjects and by imaging in 30% to 67% of the population. While nonmalignant thyroid abnormalities are quite common, 5% to 20% of nodules may contain malignancy on excision. Studies suggest that 33% of subjects have thyroid cancer on autopsy, and that approximately 50% of the population may have microscopic thyroid cancer.
Carcinoma of the thyroid accounts for approximately 3.8% of cancers in the United States, with an estimated 62,450 new cases in 2015 and 75% occurring in women. It is currently the fifth leading new cancer diagnosis in women and is projected to overtake colorectal cancer as the fourth leading cancer diagnosis overall in the United States by 2030. Although the incidence of thyroid cancer has risen in recent years, perhaps due to the increased use of ultrasound, its mortality rate has remained stable with a 5-year survival of approximately 98%, accounting for 0.3% of all cancer deaths in 2015.
Key Operative Learning Points
- 1.
Identification and continued observation of the recurrent laryngeal nerve is the best way to avoid injury to the nerve.
- 2.
Skeletonize the superior pedicle and ligate close to the thyroid gland to avoid injury to the superior laryngeal nerve and parathyroids.
- 3.
Identify and lateralize the parathyroid glands with their blood supply.
- 4.
Careful placement of the incision and protection of skin edges promote optimal cosmetic results.
Preoperative Period
History
- 1.
History of present illness
- a.
Evaluate for onset, duration, change in size, growth rate, and pain.
- 1)
Asymptomatic nodules are often found on imaging.
- 2)
Rapid growth of a new or previously stable nodule is concerning for malignancy.
- 3)
Pain is not commonly associated with thyroid cancer and may represent thyroiditis or hemorrhage into a benign nodule.
- 1)
- b.
Compressive symptoms: Shortness of breath and dyspnea (especially with lying flat), persistent dysphagia
- c.
Invasive symptoms: Hemoptysis, fixation of the overlying skin, or hoarseness from paralysis of the vocal cord
- d.
Hyper or hypothyroid symptoms: Palpitations, weight change, fatigue, anxiety, sleep disturbance, or menstrual changes
- a.
- 2.
Risk factors for thyroid cancer
- a.
Age
- 1)
Less than 20: ∼20% risk of malignancy in a solitary nodule
- 2)
20 to 40: 5% to 10% risk of malignancy in a solitary nodule
- 3)
Peak in women 45 to 50, men 65 to 70
- 1)
- b.
Gender: There is a triple prevalence in women, but thyroid nodules in men are more likely to be malignant.
- c.
Two or more first-degree relatives with a history of thyroid cancer
- d.
Exposure to low dose radiation to the neck
- a.
- 3.
Past medical history
- a.
Hashimoto’s thyroiditis
- 1)
Nodules are 30% more likely to contain papillary thyroid cancer.
- 2)
Increased risk of lymphoma
- 1)
- b.
Consider multiple endocrine neoplasia type 2 (MEN-2) and medullary thyroid carcinoma in patients with pheochromocytoma, hyperparathyroidism, marfanoid habitus, and/or mucosal neurofibromas.
- c.
Gardner syndrome (polyposis coli) and Cowden disease are associated with thyroid cancer.
- a.
Physical Examination
- 1.
Complete examination of the head and neck.
- a.
Palpate thyroid for enlargement and nodules.
- 1)
Note size, shape, firmness, movement with swallowing, fixation to skin, or underlying structures.
- 1)
- b.
Palpate neck for lymphadenopathy.
- c.
Listen for hoarseness, stridor.
- a.
- 2.
Direct or indirect laryngoscopy
- a.
This is essential in detecting vocal cord paralysis.
- b.
The voice may be normal despite a paralyzed vocal cord.
- a.
Laboratory Studies
- 1.
Thyroid stimulating hormone (TSH)
- a.
Initial study of choice to rule out hypo or hyperthyroidism
- a.
- 2.
Thyroglobulin (Tg)
- a.
Cannot reliably differentiate between benign and malignant thyroid disease
- a.
- 3.
Calcitonin
- a.
Usually not recommended unless patient has a family history of medullary thyroid carcinoma or MEN-2, or biopsy shows medullary thyroid carcinoma
- a.
Imaging
- 1.
Ultrasound (US)
- a.
Thyroid US with attention to central compartment should be performed in all patients with a thyroid nodule, even when found on computed tomography (CT).
- b.
Provides details on size, consistency, other nodules, and associated cervical lymphadenopathy
- c.
Useful for serial monitoring of nodules and lymph nodes
- d.
Findings associated with malignancy include
- 1)
Complex nodules
- 2)
Irregular margins
- 3)
Increased nodular vascularity
- 1)
- e.
Microcalcifications are associated with markedly increased risk of malignancy, while cystic and spongiform appearance may be associated with benign lesions.
- a.
- 2.
CT and magnetic resonance imaging (MRI)
- a.
Generally not needed
- b.
Can be helpful for
- 1)
Substernal extension
- 2)
Cervical and mediastinal lymphadenopathy
- 3)
Invasion of surrounding structures such as trachea and esophagus
- 4)
Metastasis to distant body sites
- 1)
- c.
Use of iodinated contrast may preclude the use of radioactive iodine (RAI) for 1 to 3 months.
- a.
- 3.
Radionuclide scanning
- a.
Usually performed with 123 I or technetium 99m ( 99m Tc) sestamibi
- b.
Incidence of malignancy is 4% in “hot” nodules and 10% to 15% in “cold” nodules.
- c.
Not routinely performed unless TSH level indicates hyperthyroidism
- 1)
If hyperfunctioning nodule, no cytologic evaluation necessary and consideration for ablative radioiodine
- 2)
If hypofunctioning, may indicate malignancy
- 3)
Most cancers are isometabolic
- 1)
- a.
Fine Needle Aspiration
- 1.
Best initial diagnostic test
- 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 should undergo FNA in addition to that of thyroid nodules.
- 3.
When multiple nodules are present, the largest and/or most sonographically suspicious should preferentially be biopsied.
- a.
Multiple nodules may need to be biopsied to increase diagnostic yield.
- a.
- 4.
Bethesda classification of thyroid cytopathology
- a.
I: Nondiagnostic, 1% to 4% risk of malignancy
- b.
II: Benign, 0% to 3% risk.
- c.
III: Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS), 5% to 15% risk.
- 1)
This is a gray zone where repeat FNA, observation with serial US, and surgery are all potential options.
- 1)
- d.
IV: Follicular neoplasm, 15% to 30% risk
- e.
V: Suspicious for malignancy, 60% to 75% risk
- f.
VI: Malignant, 97% to 99% risk
- a.
Molecular Biomarkers
- 1.
Newer studies introduced to increase accuracy of FNA and better characterize the risk of malignancy, especially in indeterminate cytology, AUS, and FLUS lesions. 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
- a.
- 2.
Examples: BRAF, RAS, TIMP1, RET/PTC, Pax8-PPARγ, galectin-3, cytokeratin, microRNA, gene sequencing
- 3.
Uncertain evidence regarding efficacy and utility
Indications
Total Thyroidectomy
- 1.
Differentiated thyroid carcinoma if one or more of the following:
- a.
Tumor greater than 4 cm
- 1)
Between 1 and 4 cm: Option of lobectomy or total thyroidectomy
- 1)
- b.
Gross extrathyroidal extension
- c.
Contralateral thyroid nodule or cervical/distant metastasis
- d.
Multinodular goiter with radiation exposure to head and neck
- e.
First degree family members with thyroid cancer
- a.
- 2.
Medullary thyroid carcinoma
- 3.
Anaplastic thyroid carcinoma, depending on resectability
- 4.
Bilateral indeterminate nodules
- 5.
Multinodular goiter causing compressive symptoms
- 6.
Medically refractory Grave’s disease or hyperthyroidism
Thyroid Lobectomy
- 1.
Papillary or follicular thyroid carcinoma if all of the following:
- a.
Less than 4 cm
- b.
Low-risk pathology
- c.
Unifocal/solitary thyroid nodule
- d.
Intrathyroidal
- e.
No prior head and neck radiation
- f.
No cervical metastasis
- a.
- 2.
Isolated, indeterminate nodule (AUS, follicular neoplasm, or suspicious for carcinoma)
- a.
Patient may elect for total thyroidectomy to avoid completion thyroidectomy
- a.
- 3.
Benign nodule greater than 3 to 4 cm
- 4.
Nodule causing compressive symptoms
Contraindications
- 1.
Uncontrolled, severe hyperthyroidism (relative contraindication)
- a.
Risk of intraoperative thyroid storm
- a.
- 2.
Pregnancy (relative)
- 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.
Prohibitive comorbid medical conditions
Preoperative Preparation
- 1.
Screen for comorbidities.
- 2.
Document vocal cord movement with indirect laryngoscopy prior to surgery.
- 3.
Assure euthyroid state.
Operative Period
Anesthesia
- 1.
Administer general endotracheal anesthesia.
- 2.
Local anesthesia with sedation may be considered with significant comorbidities such as poor cardiac function, or in pregnant patients.
Positioning
- 1.
Supine
- a.
Shoulder roll to slightly extend neck and elevate thyroid
- b.
Head placed in a donut to prevent rotation
- a.
- 2.
The bed can be shifted away from anesthesia to provide more surgical space.
- 3.
The back may be elevated 10 to 30° to reduce venous congestion.
- 4.
Prepare neck and upper chest with povidone-iodine or chlorhexidine (entire chest if sternotomy anticipated for a substernal goiter).
- 5.
Arms tucked at the side with padding of elbows and heels.
Perioperative Antibiotic Prophylaxis
- 1.
Perioperative antibiotics are not necessary in clean thyroid surgery.
- a.
A single preincision intravenous dose of broad-spectrum antibiotic such as second-generation cephalosporin or clindamycin antibiotic is acceptable.
- a.
Monitoring
- 1.
Intraoperative laryngeal nerve monitoring (IONM) may be used.
- a.
Endotracheal tube with surface electrodes placed at level of vocal cords
- b.
Becoming increasingly popular but efficacy is controversial
- c.
No difference in rate of vocal cord palsy between visual identification and IONM
- d.
Increased cost and setup time
- e.
Not a substitute for gold standard of visual identification and careful dissection
- f.
Useful adjunct for identification of the recurrent nerve, which may result in decreased operative time and increased surgeon comfort
- a.
Instruments and Equipment
- 1.
Basic head and neck set
- 2.
Ultrasonic scalpel (preferred by the senior author for its hemostatic ability and speed) and bipolar cautery
- 3.
Mahorner, Lone Star, or Weitslander self-retaining retractors may be helpful if an assistant is not available.
- 4.
Kittner/peanut sponges 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 dissection of nerves
- a.
- 7.
Surgical clips
Key Anatomic Landmarks
- 1.
Embryology
- a.
Thyroid gland arises from the first and second pharyngeal pouches at the foramen cecum.
- b.
It descends along the thyroglossal duct, anterior to the hyoid bone, to its final position overlying the second to fourth tracheal rings.
- a.
- 2.
Thyroid gland
- a.
Lateral lobes: 4 to 5 cm tall, 1 to 2 cm wide, 2 to 4 cm thick
- b.
Isthmus: 12 to 15 mm wide, absent in 5% to 10%
- c.
Pyramidal lobe: Remnant of the thyroglossal duct, found as a superior extension of the isthmus in 40% to 50%
- d.
Tubercle of Zukerkandl: Remnant of the lateral thyroid processes (ultimobranchial bodies), found as posterolateral projection (sometimes bifid) of each lobe in 63% to 78%
- e.
Lies within the middle layer of the deep cervical fascia (pretracheal fascia)
- f.
Attached by ligaments that are extensions of a thin but tightly adherent capsule, which extends as septa into the thyroid parenchyma, dividing it into lobules.
- 1)
Superomedial: Anterior suspensory ligament to thyroid and cricoid cartilages
- 2)
Posteromedial: Posterior suspensory ligament (Berry’s ligament) to first and second tracheal rings and cricoid cartilage
- 1)
- a.
- 3.
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 thyrocervical 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%
- a)
- 1)
- b.
Venous
- 1)
Superior thyroid veins: Run alongside the superior thyroid arteries and join with the internal jugular veins
- 2)
Middle thyroid veins: Join the internal jugular veins
- 3)
Inferior thyroid veins: Frequent anastomoses before joining the innominate veins
- 1)
- c.
Lymphatics: Prelaryngeal, pretracheal, paratracheal, parapharyngeal, deep cervical, and supraclavicular nodes
- a.
- 4.
Recurrent laryngeal nerve (RLN)
- a.
Emanates from the vagus nerve as it courses inferiorly, anterior to the aortic arch
- 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 larynx above the first tracheal ring, below cricoid cartilage
- 1)
- b.
Function
- 1)
External branch: All intrinsic muscles of the larynx (except the cricothyroid muscle)
- 2)
Internal branch: Sensation to the laryngeal mucosa of the glottis and subglottis
- 1)
- c.
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)
Relationship between the RLN and the inferior thyroid artery 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 Zukerkandl in 98% of patients
- 7)
Nonrecurrent laryngeal nerves can be found in up to 0.7% of patients.
- a)
Primarily on the right (associated with aberrant subclavian), 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.
- 5.
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)
Divides into internal and external branches about 2 cm above the superior pole of the thyroid, with the former penetrating through the posteroinferior thyrohyoid membrane
- 1)
- b.
Function
- 1)
Internal branch: Sensation and secretomotor function to the supraglottis, epiglottis, base of tongue, piriform sinus, and upper esophageal sphincter
- 2)
External branch: Cricothyroid and inferior constrictor muscles. Tensor of vocal cords
- 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)
The nerve is 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.
Prerequisite Skills
- 1.
Intricate knowledge of surgical instrument use and meticulous soft tissue/neural dissection
Operative Risks
- 1.
Injury to the recurrent laryngeal nerve
- a.
Preferential visual identification of the RLN before the thyroid is dissected off of the trachea
- a.
- 2.
Injury to the superior laryngeal nerve
- a.
Carefully dissect out the superior pole to ensure that the SLN is not hidden within the vascular pedicle before ligation.
- a.
- 3.
Injury to or devascularization of the parathyroid gland
- a.
Lateralize parathyroids with their blood supply when medializing the thyroid gland
- b.
Re-implant 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 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 vasculature.
- a.
Surgical Technique
Thyroid Lobectomy
- 1.
Marking
- a.
Mark a 3 to 5 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.
- c.
Mark the incision higher in younger patients, because the scar will migrate lower over time and a scar below the clavicle is often unsightly.
- 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, since the arterial supply is coming from below.
- 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 the 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 to 0 silk ties.
- c.
Protect the skin with occlusive material such as Steri-Strips (preferred by the senior author; Fig. 78.1 ).
- 1)
Suture in place with locking 2 to 0 silk running stitches
- 2)
Protects the skin from heat or instrument injury
- 1)
- a.
