Substernal Goiter Surgery

Enlarged thyroid glands (ie, goiters) often extend in the mediastinum posterior to the sternum, making the gland, by definition, a substernal (or retrosternal) goiter.[1, 2, 3, 4, 5, 6, 7, 8, 9] When this occurs, thyroidectomy surgery (excision of part or all of the thyroid gland) has unique considerations that are important to understand for the surgeon and patient.

This article reviews substernal goiter and focuses on substernal thyroidectomy.

Most substernal goiters are composed of nontoxic multinodular thyroid glands, but can also represent a generalized enlargement of the thyroid gland, an enlargement of one particular nodule, or the inferior extension of thyroid carcinoma. Most (approximately 90%) substernal thyroid masses are benign goiters.[10, 11, 12, 6, 13, 14, 15]

Goiters are often idiopathic in etiology but may be caused by the following:

• Iodine deficiency (although increases in dietary iodine, particularly with iodinated salt, have dramatically reduced the frequency of goiters in the United States)[16]

• Goitrogens (foods such as cabbage, turnips, peanuts, and soybeans and drugs such as lithium, propylthiouracil, and amiodarone)[17, 18]

• Heredity[19, 20]

• Malignancy (with risk factors including radiation exposure, family history, multiple endocrine neoplasia type 2a [MEN 2a], and MEN 2b, among others)[21]

The incidence of sporadic nontoxic goiter in the United States has been estimated to be approximately 5%. In some developing countries in which iodine deficiency is severe, up to one third of a population can be affected by goiters. Studies of chest radiographic screenings in Australia and the United States suggest substernal goiter may occur in approximately 0.02% of the population.[22, 23] In one study, mean age at diagnosis was 55.3 +/- 3.58 years, and most cases were found in women (83.3%).[70] Substernal thyroidectomy patients have been found more likely to be older, Hispanic or Black, and have Medicare insurance.[78] Reportedly, of patients undergoing thyroidectomy, up to 20% can have substernal goiters.[5, 24, 25, 26, 11, 27] The definition of a substernal goiter is currently not standardized, with great variability at which depth of thyroid extension beyond the thoracic inlet fulfills criteria.[71]

Substernal goiters can often remain asymptomatic for many years.[28, 29] Goiters are sometimes discovered incidentally during neck and chest radiography.[12, 7] However, the natural expectation of goiters is continued progressive growth, which may result in lower-neck discomfort, a noticeable neck mass, and progressive compression of the trachea, esophagus, and great vessels, thereby causing dyspnea, dysphagia/globus, and neck venous congestion/superior vena cava syndrome, respectively.[3, 26, 6, 30, 12, 70]

Substernal goiters are often more prominent on one side of the trachea and are thus highly correlated with tracheoesophageal deviation to the opposite side (see image below).[31, 3]

Independent of laterality, substernal goiters usually extend into the anterosuperior mediastinum. Unilateral extension is the most common finding with equal frequency between right and left-sided extensions.[77] With this type of extension, the recurrent laryngeal nerve is not usually displaced from the tracheoesophageal groove. Occasionally, substernal goiters may extend into the posterior mediastinum behind the trachea. Posterior mediastinal thyroid extension may displace the recurrent laryngeal nerve unexpectedly, further complicating surgical excision of the goiter.[14, 31]

The identification of substernal extension of an enlarged thyroid gland itself is generally an indication for surgery.[1, 2, 32, 33, 9, 3, 34] Many authors advocate surgical removal of substernal goiters, even when asymptomatic, for the reasons discussed below.

First, substernal goiters are highly likely to continually grow, leading to the development of compressive symptoms (rarely, but possibly, emergent). In addition, such goiters become increasingly difficult to excise with further growth over time.

Second, the risk of a substernal goiter harboring malignancy is 3%-21%.[10, 11, 12, 6, 13, 14, 15] The risk of postoperative diagnosis of thyroid cancer is increased in patients with substernal multinodular goiters compared to cervical mutinodular goiters.[73] Fine-needle aspiration (FNA) biopsy of nodules in larger substernal goiters suffers from the following factors:

• Riskier in the setting of the large-caliber blood vessels of the mediastinum

• Subject to increased sampling error

• Not possible given the barrier of the chest bones

• Unnecessary given the already present indication for removal

Substernal goiters in individuals who are not medically fit to undergo surgery or who decline excision should be evaluated for malignancy.[6] Radiologic evaluation (ultrasonography, CT scanning, or MRI) of the lateral and central neck and mediastinal lymph nodes helps to determine the likelihood of metastatic disease (see image below).[35, 36, 37]

If lymph nodes appear suspicious on preoperative imaging, FNA biopsy or intraoperative biopsy of the lymph nodes is warranted.

The presence of symptoms is another indication for substernal thyroidectomy. Negative thoracic pressure, swallowing, and gravity help direct the growing goiter into the mediastinum.[76] Compressive symptoms, as described above, are often enough to motivate a patient to seek attention and possibly request surgery. Although approximately 85% of goiters are euthyroid, a minority cause symptoms related to hyperthyroidism (eg, palpitations, irregular or rapid heart rates, weight loss, increased heat sensitivity, insomnia, nervousness, tremulousness, diarrhea) or even hypothyroidism (eg, fatigue, weight gain, increased cold sensitivity, depression, constipation, brittle hair).

Thyrotoxicity (hyperthyroidism) in goiters may result from an autonomously functioning nodule or may be precipitated by intake of iodides found in certain expectorants or in radiographic contrast media. Hyperthyroidism requires preoperative medical management to avoid thyroid storm perioperatively.

The appearance of a mass in the low anterior neck may motivate a patient enough to request surgical excision for cosmetic reasons (see image below).[38]

Rarely, the Pemberton sign (raising hands induces facial flushing, dilated neck veins, and even stridor from compressive effects of goiter) is an indication for a substernal thyroidectomy.

Surgical intervention is most often the appropriate treatment for substernal goiter. In cases of apparently benign thyroid disease, the surgery should include the removal of the substernal component and other thyroid tissue responsible for obstructive symptoms. Thus, when possible, surgery can be limited to the removal of a single lobe and the isthmus.[14]

Recurrence and extension beyond the carina were found to be main risk factors associated with postoperative complications.[80] The risk of complications is reduced when injury of the contralateral recurrent laryngeal nerve and parathyroid glands is avoided. In cases of bilateral compression or malignant disease, total thyroidectomy should be performed, particularly in tumors larger than 2 cm in which postoperative radioactive iodine treatment may be used.[21]

Close observation may be appropriate for substernal goiters that are small, without symptoms, without radiographic evidence of visceral or vascular compromise, and/or when found in a patient of advanced age or at high surgical risk. Surgeons and medical physicians, in cooperation with the patient, must weigh the risks of surgery and general anesthesia with the presence of symptoms or the possible impending dangers of mass effect of a substernal goiter.

Suppressive therapy (using exogenous thyroid hormone to suppress the pituitary secretion of thyroid-stimulating hormone and its stimulatory effects on thyroid gland growth) is generally ineffective in the management of substernal goiters. Suppressive therapy can be considered when surgical excision is contraindicated but likely would not be very effective.[2, 1, 39, 34, 40]

Radioactive iodine therapy may be useful in the treatment of hyperthyroidism associated with goiters, but not in the reduction of compressive symptoms.[41]

Procedure Planning

Physical examination

Along with a full neck examination, the physical examination (see image below) should include an assessment for the Chvostek sign (found in 10% of cases at baseline when eucalcemic) to determine if this reflex may be used to assess possible postoperative hypocalcemia.

A preoperative vocal cord examination can help determine the baseline condition and laryngeal function (see image below).[14] Patients with substernal goiters have been found to exhibit signs of laryngopharyngeal reflux at preoperative laryngoscopy.[81]

Blood tests

The following blood tests can be helpful preoperatively:

• Thyroid-stimulating hormone (TSH)

• Free thyroxine (FT4)

• Calcium

• Albumin

• Parathyroid hormone (PTH)

TSH and FT4 are used to assess thyroid hormone production and the need for preoperative treatment of hyperthyroidism or thyroid hormone replacement in cases of hypothyroidism. Calcium, with albumin correction, and PTH can help predict the need for calcium (and vitamin D) replacement after thyroidectomy.

Imaging studies

When the presence and degree to which a goiter has substernal extension is unknown, CT scanning or MRI of the neck and chest can help assess both the need for surgery and preoperative planning.[42, 12] For example, one study shows that a CT-determined thyroid volume of ≥162 cm3 extending below the thoracic outlet was indicative for an extra-cervical approach.[79]

If CT scanning is performed, a scan without contrast is recommended by many. The iodine contained in contrast agents can reduce the uptake and efficacy of postoperative radioactive iodine used in addition to thyroidectomy for the treatment of thyroid malignancy. Iodinated contrast can reduce the efficacy of radioactive iodine for up to 6 months.

Ultrasonography is often an integral and recommended component of thyroid evaluation because of its detailed imagery, potential for directed biopsies, minimal risk profile, and lower cost. However, ultrasonography is not capable of visualizing substernal components of the thyroid gland because the bones of the chest (clavicles, ribs, manubrium, sternum) block the transmission of acoustic information.

Chest radiography and iodine-123 (I123) nuclear medicine scans can show a substernal goiter, but without much anatomic detail of the gland or the surrounding structures.

Barium esophagraphy may show indentation and deviation of the esophagus, suggesting a certain length of substernal goiter causing mass effect. However, the usefulness of esophagraphy is limited given its inability to accurately confirm a thyroid mass because of poor anatomic detail.

Complication Prevention

Overall, complications of substernal thyroidectomy are rare (< 5%).[1, 29, 26, 43] Effective, safe, and sterile surgical technique is important for minimizing the possible complications of substernal thyroidectomy (bleeding, hematoma, infection, hypoparathyroidism/hypocalcemia, injury to the external branch of the superior laryngeal nerve, and/or recurrent laryngeal nerve injury) and midline sternotomy (hematoma, seroma, mediastinitis/abscess/osteomyelitis, chest bone fracture, sternum shift/disfigurement or dehiscence, pneumothorax/pneumomediastinum).[5] Appropriate use of a midline sternotomy by a surgeon trained to do so is important. Indications for a midline sternotomy include ectopic thyroid tissue in the mediastinum, extension of goiter below the aortic arch, and large thyroid tissue extending towards the tracheal bifurcation.[72]

Prediction, identification, and treatment of postoperative hypoparathyroidism and hypocalcemia are important for the safety of the patient.

Physicians should educate patients concerning the need (or possible need in the case of thyroid lobectomy surgery) for daily thyroid hormone supplementation and possible future necessary dose adjustments.

To reduce the risks of continued hyperthyroidism, including the development of perioperative thyroid storm (acute, life-threatening elevations of thyroid hormone levels), surgeons, primary care physicians, internists, endocrinologists, and anesthesiologists should work to identify hyperthyroidism preoperatively, to reduce the hormone effects and production with medications such as beta-blockers and possibly antithyroid thioamides (propylthiouracil and methimazole), and to have medications (beta-blockers, propylthiouracil, sodium iodine, corticosteroids) available during and after the operation to reduce acute effects.

If signs of thyroid storm develop during substernal thyroidectomy, the surgical team should halt the surgical procedure.

The goals of substernal thyroidectomy are as follows:

• Complete excision without surgical complications

• An incision and resulting scar as small and as safe as possible

• Resolution of symptoms and/or hyperthyroidism

• Cosmetic improvement with removal of low anterior neck mass

• Determination of the presence of malignancy

Potential complications of substernal thyroidectomy

Injury to the recurrent laryngeal nerve due to thyroidectomy has a reported incidence in the literature of 1%-5% for temporary paralysis and 2% or lower for permanent paralysis.[44, 45, 46, 47, 48, 49] In some studies, risk of injury to the recurrent laryngeal nerve was not increased in operations with sternotomy.[74]

Injury to the external branch of the superior laryngeal nerve due to thyroidectomy has a reported incidence in the literature of 0%-20% (mostly 5%-10%) for temporary paralysis and 5% or lower for permanent paralysis.[50, 49, 51, 52]

Postoperative hypoparathyroidism due to total thyroidectomy (not in cases of lobectomy) has a reported incidence in the literature of 0.3%-17.5% for temporary dysfunction and 0%-3.4% for permanent dysfunction.[53, 54, 55, 48, 49] It is often possible to identify and preserve the parathyroid glands during surgery.[75] Risk of hypoparathyroidism in operations with sternotomy have been shown to be the same in operations without sternotomy.[74]

Hematoma and infection due to thyroidectomy each has a reported incidence of less than 2%.[54, 45]

Seroma formation due to thyroidectomy has a reported incidence of 1%-6%.[54, 45]

Hypothyroidism is an expected outcome of total thyroidectomy. Thyroid lobectomy also has a reported incidence of 18%-50%.[56, 57, 58, 59] Patients with Hashimoto thyroiditis and/or elevated anti-TPO antibody levels appear to be at an increased risk of hypothyroidism after thyroid lobectomy.[60] If lymphocytic infiltration and germinal center formation are found in the lobectomy pathologic specimen, thyroid replacement may become increasingly necessary.[61]

Randolph et al (2011) found that bilateral goiters larger than 9 cm in diameter and/or heavier than 40 g (including some substernal goiters) are a risk factor for difficult intubation, recurrent laryngeal nerve injury, and postoperative hypocalcemia.[62] The degree of goiter extension was found to be directly related to risk of postoperative dysphonia.[82] Others studies corroborate the findings of increased risks of vocal cord dysfunction and hypocalcemia with substernal goiter surgery.[63, 4] However, Raffaelli et al (2011) found no increased rate of complications with substernal thyroidectomy compared to non–substernal thyroidectomy.[5]

With total thyroidectomy for bilateral goiter, the risk of recurrence is virtually zero.[64] Thyroid lobectomy and cases in which a thyroid cancer is excised carry the risk of recurrent disease depending on the extent and stage of each disease.

Adequate education about the diagnosis, ramifications, indications, and reasons for substernal thyroidectomy is a very important part of the clinical conversation between a treating physician and patient.

In addition, obtaining informed consent with an explanation of the steps of the operation, risks, benefits, and possible alternatives of the surgery is crucial.

Elements of Informed Consent

The example below illustrates the range of elements that are important for a surgeon to convey to a patient undergoing substernal thyroidectomy presented in language that minimizes the use of complex medical terminology as it might in a patient handout.

Steps of the operation

A substernal thyroidectomy involves the following steps:

1. Skin incision horizontally along the front aspect of the lower neck and possibly in a vertical fashion down the midline of the upper chest

2. Dissection through the tissues overlying the thyroid and along the circumference of the gland

3. Identification and/or avoidance of the parathyroid glands (two on each side), the superior and recurrent laryngeal nerves (on each side), and the major blood vessels in the neck and upper chest

4. Removal of a thyroid lobe or the entire gland

5. Potential vertical split of the sternum bone with a special surgical saw

6. Potential placement of a flexible plastic drain to remove excess fluid from underneath the skin flaps (to encourage proper healing)

7. Skin closure with sutures and possibly staples

Postoperative hospitalization

Patients who are in good health may be able to go home on the day of surgery in some cases. Some patients may need to stay in the hospital after surgery for 1-2 days.

Benefits of surgery

Benefits of the surgery should include the following:

• The removal and treatment (and reduction of recurrence risk) of benign or malignant tumors or an enlarged thyroid gland (ie, goiter)

• The resolution of compression of the trachea, esophagus, and/or major blood vessels, with the associated symptoms

• The resolution of hyperthyroidism and its symptoms

• Determination of the presence of cancer and the possible need for additional treatment

Alternatives to surgery

In some cases, waiting and observing with regular clinic appointments and possibly radiologic images is an option. For hyperthyroidism, medical therapy is still an option in some cases.

These issues should be discussed carefully between the surgeon and patient.

Risks/possible complications

All types of surgery carry some risk. Complications associated with substernal thyroidectomy surgery are rare (some very rare). Substernal goiters that require extensive dissection may be associated with a somewhat greater risk than standard thyroidectomy;[4] however, many surgeons and authors feel that the rate of complications associated with removal of substernal goiters is similar those associated with standard thyroidectomy.[14, 12] Under the care of well-trained surgeons, the benefits of surgery usually outweigh these risks and potential complications.

Potential risks are discussed below.

Low thyroid hormone levels in the blood (hypothyroidism): A thyroidectomy decreases or completely removes the body’s ability to make thyroid hormone (a hormone that helps to control the body’s function and metabolism). Thus, after a total thyroidectomy, the patient will need lifelong thyroid hormone replacement in the form of a pill that is taken daily. After a partial or hemithyroidectomy, the remaining gland is usually able to make a normal amount of hormone; however, further blood tests after surgery will determine the need for hormone replacement.

Unwanted scar: All incisions performed during surgery result in scars. Hypertrophic scars or keloids (overabundant scar tissue) that develop in some patients can often be treated.

Numbness: All patients who undergo thyroidectomy experience some numbness of the skin of the neck above and below the incision. Some sensation may return over months to years.

Sore throat due to intubation: Some patients develop a sore throat for the first few days after surgery from the breathing tube being in their throat during the operation. Rarely, the breathing tube may cause inflammation that lasts longer than a few days.

Low calcium levels: The parathyroid glands, which are located next to the thyroid gland, produce a hormone that maintains the appropriate amount of calcium in the blood stream. In some cases, surgery temporarily or permanently disrupts the glands’ function, leading to low blood levels of calcium, which can result in numbness and tingling around the mouth, hands, and feet and muscle spasms. Without calcium replacement, seizures and problems with the heart’s rhythm may develop. Low calcium levels are treated with calcium and possibly vitamin D supplements to restore the normal calcium balance. These medications are continued until parathyroid function improves. If parathyroid function does not improve with time, the patient may need lifelong calcium medication. Permanent parathyroid dysfunction is a rare complication. With hemithyroidectomy surgery (one thyroid lobe being excised), the risk of parathyroid gland dysfunction is extremely low.

Bleeding/hematoma: A collection of blood can develop under the skin flaps and may prolong healing. This is more common in patients who are taking blood-thinning medications (eg, warfarin, clopidogrel, aspirin, ibuprofen, naproxen). Treatment may involve observation, antibiotics, or a reoperation to open up the skin to remove the clot.

Seroma: A collection of fluid can develop under the skin flaps and may prolong healing. Treatment may involve observation, needle aspiration, or the sterile insertion of another drain to release the fluid.

Infection/abscess/bone infection: Treatment may involve antibiotics and, possibly, an incision to drain a pus collection.

Recurrent laryngeal nerve injury: This injury (temporary or permanent) is a rare complication that can result in partial or complete paralysis of the vocal cord on the side of the injury. This can cause a breathy or hoarse voice and possible aspiration of secretions into the lungs. Often, the other vocal cord acts more strongly to maintain the voice and lung protection. Vocal cord function can return in many cases over a few weeks to several months. If injury is prolonged or permanent, the vocal cord can be injected with a material to increase its bulk, allowing more appropriate vocal cord closure and better voice quality.

Superior laryngeal nerve injury: This injury (temporary or permanent) is a rare complication that can result in partial or complete paralysis of the cricothyroid muscle. This can cause some speech and singing problems. Function can return in many cases over a few weeks to several months.

Chest bone fracture: Breaking one or more of the chest bones is rare but possible with the split of the sternum. Usually, any breaks heal on their own without treatment beyond pain control.

Sternum disfigurement: Rarely, a shift of the closure of the sternum split can result in a raised portion of bone or an asymmetrical appearance of the bone. This may or may not need treatment.

Sternum dehiscence: Complete separation of the closure of the sternum split is very rare. This is an emergency that requires a return to the operating room for reclosure.

Pneumothorax and/or pneumomediastinum: Air can develop in the chest and/or around the lungs as a result of uneventful surgery or more rarely from a lung injury. If the amount of air is small enough, the air can be observed without treatment with the expectation of full reabsorption. If there are symptoms of difficulty breathing or chest pain and/or the amount of air is large enough, a catheter or tube may need to be inserted through the skin into the chest to evacuate the air.

Prior to surgery, the patient should be advised of the steps of the operation and recovery, risks, benefits, and possible alternatives.

Preoperative management should include reducing the risk of thyroid storm through medical evaluation and treatment, preparation for possible airway difficulties during intubation, and a thorough comprehension of the anatomic aspects of the particular patient being treated for appropriate surgical planning.

All patients undergoing any thyroid surgery should undergo preoperative thyroid function studies and appropriate medical management of any thyrotoxicity.

Intubation can be more challenging with distortion of the position of the larynx, narrowing of the trachea, and changes to expected anatomy with neck extension.[42] Therefore, a preoperative evaluation by the anesthesia team and a discussion between the surgeon and anesthesiologist regarding airway management should be undertaken. The anesthesiologist should be prepared to perform a fiberoptic intubation, if indicated, to ensure successful intubation.[65]

Consultation with and the availability of a surgeon with expertise in midline sternotomy are important to ensure that the proper exposure is possible for the substernal goiter. Poor exposure in the mediastinum can lead to damaging complications in substernal thyroidectomy.[4, 66, 47, 63, 24, 6]

Preoperative clearance by a primary care physician and/or cardiologist, pulmonologist, or other specialists should be obtained, when necessary. If possible, patients should discontinue blood-thinning agents such as aspirin, naproxen, ibuprofen, clopidogrel, and warfarin.

Equipment involved in substernal goiter surgery includes the following:

• Tegaderm for eyes

• Head rest

• Shoulder roll

• Laryngeal nerve monitor endotracheal tube (this is recommended by some surgeons and authors to help identify and assess for inadvertent manipulation of the superior and recurrent laryngeal nerves)

• Nasogastric tube to help identify esophagus intraoperatively with palpation

• Foley catheter

• Head lights

• Ink marker

• 1% lidocaine/1:100,000 epinephrine

• Chlorhexidine soap

• Split drapes

• No. 15 blade

• Elastic hooks for skin flaps

• Multiple forceps, dissectors, clamps, scissors, and retractors of various sizes and angles

• Sharp rakes

• Double-pronged skin hooks

• Suction

• Unipolar cautery (paddle tip)

• Bipolar cautery (jeweler and/or bayonet)

• Ligation device

• Automatic surgical clip applier

• Cotton pledgets with epinephrine 1:1000 for topical use only (with yellow fluorescein to reduce risk of injection)

• 7-10F flat Jackson Pratt drains

• 3-0 nonabsorbable monofilament sutures

• 2-0/3-0 silk free ties (multiple)

• 3-0 absorbable multifilament suture on pop-off-tapered needles

• 4-0 absorbable monofilament suture on tapered needles

• 5-0 nonabsorbable monofilament suture

If midline sternotomy is performed, additional equipment is as follows:

• Sternotomy saw

• Sternotomy self-retaining retractor

• Bone wax

• Vessel loops

• Sternal wires (for closure of sternum)

Anesthesia

General anesthesia is used for this procedure. Paralysis is not used to allow for laryngeal nerve monitoring (if used).

Awake oral or nasal fiberoptic endoscopic intubation with topical local anesthesia should always be considered in cases involving oropharyngeal, laryngeal, or tracheal abnormalities (eg, laryngeal deviation, vocal cord paralysis, tracheal compression).

Laryngeal nerve monitoring tube may be used during the operation.

Positioning

The patient is placed in the supine position with arms padded and tucked.

The head of the bed is slightly raised to encourage venous return and to allow fluids to flow in an expected direction during dissection.

Some surgeons operate with the head of bed at the anesthesia station; others prefer a 180° turn.

During the hospitalization, the following issues should be managed by the surgeon:

• Pain control: Acetaminophen, low-dose opioid orally and/or intravenously, as needed

• Nausea control: Antinausea medications intravenously, as needed

• Drain output: Monitoring and removal when output is low enough

• Antibiotics, depending on the surgeon’s judgement and preferences

• Moisturization of the wound

• Thyroid hormone (levothyroxine) replacement with starting dose dependent on the patient’s weight, age, and other medical problems

• Deep venous thrombosis prophylaxis during the hospitalization with sequential compressive devices, regular ambulation, and possibly subcutaneous heparin or enoxaparin determined by the surgeon’s judgement and preferences

• Incentive spirometry to help encourage lung inflation

• Monitoring perioral and digital (fingertips and toes) paresthesias as an indication of possible low blood calcium levels

• Blood tests for calcium (and possibly albumin and PTH), as determined by the surgeon’s judgement and preferences

• Replacement of calcium and/or vitamin D, as determined by the surgeon’s judgment and preferences

If a midline sternotomy is performed, the following additional measures should be taken:

• Chest radiography to evaluate for possible pneumothorax/pneumomediastinum

• Movement restrictions to allow sternum to adequately heal

Follow-up

The patient is usually seen 7-10 days after surgery for a wound check, possible suture removal, possible vocal cord examination, possible final pathology report discussion, and possible blood calcium test.

Most substernal goiters can be excised via a cervical approach; however, in cases of very inferior extent or increased vasculature or in cases of recurrent goiters or thyroid cancer, a midline sternotomy may be necessary for exposure, safety, and completion of the excision.[5, 14, 6, 67]

After obtaining informed consent, the patient is brought to the operating room and placed on the bed in the supine position. The patient undergoes endotracheal intubation with laryngeal nerve monitoring electrodes, if desired by the surgeon. General anesthesia is administered. The head of the bed is rotated 180° from the anesthesiologist.

A headrest and shoulder roll with neck extension can be used to help raise the thyroid gland in some cases.

A horizontal incision is planned with an ink marker across the lower anterior neck in a relaxed skin tension line, if possible, and to a length that is appropriate for safe dissection and removal of the size of the goiter. If a partial midline sternotomy becomes necessary, plan for a midline vertical limb from the horizontal incision to the halfway point along the sternum toward the xiphoid process.

A local anesthetic and vasoconstrictive solution (such as 1% lidocaine with 1:100,000 epinephrine) is injected into the planned incision area.

The patient is prepared with sterile soap (eg, chlorhexidine) and draped in a sterile fashion.

An incision is made with a sharp blade through the skin, dermis, subcutaneous tissue, and platysma (where present). A superior subplatysmal flap is made to the level of the thyroid notch. An inferior subplatysmal flap is made to the level of the clavicles and manubrium. The skin/platysmal flaps are secured open to the drapes with either elastic hooks or suture with clamps. Attention to the location of the anterior jugular veins at this point is important since their course is deep to the platysma and superficial to the strap musculature (sternohyoid and sternothyroid).

When the thyroid gland is enlarged in a horizontal fashion, defining and dissecting out the course of the anterior border of the sternocleidomastoid on both sides may be helpful in liberating some of the lateral aspect of the goiter and generating more anatomic landmarks. This may be unnecessary depending on the size and shape of the thyroid gland.

The midline of the strap muscles (sternohyoid and sternothyroid) is then dissected and defined. On each side, individual strap muscles (or both together) are dissected free lateral to the thyroid gland. Retractors are used to pull the strap muscles away from the thyroid gland to enable continued capsular dissection. If necessary for increased exposure, the strap muscles may be incised horizontally midway down the latitude of the thyroid gland. After the thyroid has been excised, they should be reapproximated with absorbable suture.

Capsular dissection of the thyroid is important when freeing any part of the thyroid from the contents of the central lymph node compartment to reduce the risk of damaging the surrounding structures, which include the following:

• Recurrent laryngeal nerves

• External branch of the superior laryngeal nerves

• Vagus nerves

• Parathyroid glands

• Cricothyroid muscle

• Larynx

• Trachea

• Major blood vessels (superior, middle, inferior thyroid veins; superior and inferior thyroid arteries; brachiocephalic artery and vein; subclavian artery and veins; carotid arteries; internal jugular veins)

Surgeons and surgical authors vary in the sequence they follow for excising the thyroid gland and in the need for identifying the recurrent laryngeal nerves and parathyroid glands.

Regardless of sequence, careful dissection, ligation, and division of the superior, lateral, and inferior pole vessels releases the gland from the central compartments bilaterally. Preservation of inferior thyroid vessels increases the likelihood of maintaining parathyroid function. Once the gland has been retracted anteromedially beyond the region of the recurrent laryngeal nerve and on to the trachea, disconnection of the thyroid gland from the trachea by dividing Berry ligament completes the excision (see image below). A lateral-to-deep dissection course is likely much safer than a medial deep dissection with regard to the recurrently laryngeal nerves.

The superior pole vessels (superior thyroid artery/vein) and middle thyroid veins can be ligated prior to substernal/mediastinal dissection in an effort to liberate the gland and increase the mobility of the inferior aspect of the gland. The safety of inferior thyroid border dissection without a partial midline sternotomy must be judged taking into consideration the possible position of the inferior thyroidal blood vessels, parathyroid glands, and the recurrent laryngeal nerves.

If the inferior aspect of the thyroid gland is safely reachable from the neck, no partial midline sternotomy is necessary. If the dissection of the inferior aspect of the gland appears to be risky, a midline sternotomy should be performed. Prior to the surgery, a surgeon must explain to the patient the possibility of a sternotomy and have available or be a surgeon experienced with sternotomy. (For more information, see Midline Sternotomy)

Once the thyroid lobe or gland is excised, it should be oriented for the pathologist with sutures (see images below).

The gland should be examined along its entire surface for the presence of parathyroid glands. If found, obtain a frozen section confirmation of parathyroid tissue by a pathologist. Once confirmed, the parathyroid tissue is minced with a sharp blade. The minced tissue is then inserted into a sternocleidomastoid, strap, or forearm muscle and marked with a thick colored suture or a series of metal clips (to make it locatable for possible excision in the future).

After excision of the thyroid lobe or gland, the trachea is assessed for any residual displacement or distortion. If tracheomalacia with residual narrowing or kinking of the lumen is present, the tracheal airway may be improved by using traction sutures placed around cartilaginous rings. The sutures can be secured to strap muscles or even brought out through the skin tied over a button.

The wound bed is irrigated, and hemostasis is achieved, where necessary.

If a midline sternotomy is performed, a sternal wire closure or plates-and-screws closure of the chest is necessary to encourage appropriate symmetrical bone healing.

An active drain(s) may be placed into the mediastinum through the thyroid bed and out the neck. A drain from the mediastinum and another drain from the thyroid bed is a reasonable possibility. The neck drain is secured in place with a monofilament nonabsorbable suture to the skin.

The strap muscles should be closed vertically (and horizontally, if necessary) with absorbable suture in order to prevent the tracheal rings from adhering to the skin, which can cause the tracheal rings to be visible through the skin and can move the skin when the patient swallows, both of which are considered noncosmetic. The skin flaps are then closed in 3 layers with a braided absorbable suture for the platysma layer, a monofilament absorbable suture for the dermal layer, and a monofilament nonabsorbable suture or set of staples for the skin layer.

The patient is then cleaned up, awakened, extubated, and wheeled to the recovery room.

If a partial midline sternotomy is performed, the following steps should be taken:

• Dissection and isolation of the suprasternal notch

• Careful longitudinal division of the superior half of the sternum with a sternal saw

• Control of bone marrow bleeding (with cautery and/or bone wax)

• Lateral retraction of the sternum with a self-retaining device

• Dissection of the anterior fascia layer of the superior mediastinum (see image below)

  The left thyroid lobe being retracted anteromedially beyond the region of the left recurrent laryngeal nerve (pointed out by metal rod) with Berry ligament still connecting the lobe to the trachea.

With the increased exposure of a sternotomy, the goiter can continue to be dissected free of the surrounding tissue in the mediastinum and neck. Once the goiter or lobe has been excised and all bleeding is controlled, the sternum should be closed with metal wires.

The steps preceding and following performance of the sternotomy are described in Transcervical Excision of Substernal Goiter.

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Class Summary

Thyroid hormone replacement is administered to correct hypothyroidism. The starting dose depends on the patient’s weight, age, and other medical problems.

Levothyroxine (Synthroid, Levoxyl, Levothroid, Tirosint, Unithroid)

In its active form, levothyroxine influences the growth and maturation of tissues. It is involved in normal growth, metabolism, and development. Endocrinologists can monitor and adjust the doses to optimal effect. A serum free thyroxine value in the upper third of the reference range is the goal.

Class Summary

Calcium supplementation restores serum calcium levels. These medications are continued until parathyroid function improves. If parathyroid function does not improve with time, the patient may need lifelong calcium medication.

Calcium carbonate (Oystercal, Caltrate, Oysco 500, Tums E-X, Children's Pepto)

Calcium carbonate is indicated to restore and maintain normocalcemia when hypocalcemia is not severe enough to warrant rapid replacement. It is used orally as supplementation to intravenous calcium therapy. Calcium carbonate moderates nerve and muscle performance by regulating the action potential excitation threshold. Amounts of elemental calcium in calcium carbonate tablets are as follows: Tums, 200 mg; Rolaids, 220 mg; Os-Cal, 500 mg.

Calcium citrate (Calcitrate, Cal-Citrate 225, Cal-Cee)

Calcium citrate is an oral formulation usually used as supplementation to intravenous calcium therapy. Calcium moderates nerve and muscle performance by regulating the action potential excitation threshold and facilitating normal cardiac function. Give the amount needed to supplement dietary intake so as to reach recommended daily amounts. The amount of elemental calcium in 1000 mg of calcium citrate is 210 mg.

Class Summary

Low calcium levels may be treated with vitamin D supplements and calcium to restore the normal calcium balance. These medications are continued until parathyroid function improves. If parathyroid function does not improve with time, the patient may need lifelong calcium medication.

Ergocalciferol (Calciferol, Drisdol)

Ergocalciferol is the most widely available form of vitamin D. Ergocalciferol stimulates calcium and phosphate absorption from the small intestine and promotes calcium release from bone into the blood.

Cholecalciferol (Vitamin D3, Ddrops Kids, Delta-D3)

Cholecalciferol is a dietary supplement used to treat vitamin D deficiency or for prophylaxis.

Class Summary

These agents reduce many of the symptoms of thyrotoxicosis, including tachycardia, tremor, and anxiety. Usually, propranolol is recommended because of central nervous system (CNS) penetration, but some patients prefer longer-acting beta blockers. Patients note an immediate improvement in tachycardia, anxiety, heat intolerance, and tremor.

These agents are used to reduce the risks of continued hyperthyroidism, including the development of perioperative thyroid storm (acute, life-threatening elevations of thyroid hormone levels).

Propranolol (Inderal, InnoPran XL)

This is the drug of choice in treating cardiac arrhythmias resulting from hyperthyroidism. It controls cardiac and psychomotor manifestations within minutes.

Atenolol (Tenormin)

Atenolol selectively blocks beta1 receptors, with little or no effect on beta2 types.

Class Summary

These agents inhibit T4 and T3 synthesis and are used to reduce the risks of continued hyperthyroidism, including the development of perioperative thyroid storm (acute, life-threatening elevations of thyroid hormone levels).

Propylthiouracil

Propylthiouracil is a derivative of thiourea that inhibits organification of iodine by the thyroid gland. It blocks oxidation of iodine in the thyroid gland, thereby inhibiting thyroid hormone synthesis; the drug inhibits T4-to-T3 conversion (an advantage over other agents).

Propylthiouracil is available as a 50-mg tablet. It is readily absorbed and has a serum half-life of 1-2 hours. It is highly protein bound in the serum. The drug's duration of action is longer than its half-life, and propylthiouracil should be dosed every 6-8 hours (although it can be administered twice daily).

If patient compliance is an issue, methimazole is better choice because of daily dosing.

Thyroid hormone levels (TSH, T4, FTI or FT4, and T3) should be reassessed in 4 weeks and increased if thyroid hormone levels have not significantly fallen or decreased if thyroid hormone levels have fallen by 50% or more (even if still thyrotoxic). Usually, after thyroid function improves, the dose should be gradually decreased to 50-150 mg/d in divided doses (or the patient will become hypothyroid).

Methimazole (Tapazole)

Methimazole inhibits thyroid hormone by blocking oxidation of iodine in the thyroid gland. However, it is not known to inhibit peripheral conversion of thyroid hormone. The drug is available as 5-mg or 10-mg tablets. It is readily absorbed and has a serum half-life of 6-8 hours. Methimazole is less protein bound than propylthiouracil and is generally not used in pregnancy because of increased placental transfer and risk of a rare fetal condition (cutis aplasia). It has higher transfer rate into the milk of lactating women.

Methimazole's duration of action is longer than its half-life, and the drug should be dosed every 12-24 hours. Studies have shown that rectal suppositories or retention enemas can be used at the same dose as orally administered methimazole for patients who cannot take oral medications. Usually, after thyroid function improves, the dose must be decreased, or patient will become hypothyroid.