Prior to the 20th century, thyroid surgery was associated with a high operative mortality rate. The meticulous surgical technique advanced by Kocher in the late 1890s transformed thyroidectomy into a safe operative procedure associated with a 1% mortality rate. Although generally safe and effective, surgery for massive and substernal goiter remains subject to potentially significant surgical complications.
Approximately 5% of the population in the United States is estimated to have benign enlargement of nodules within the thyroid gland, known as a goiter. Iodine deficiency has been associated with the development of goiter, but this cause of goiter is now uncommon in the developed world. The vast majority of goiters are not associated with abnormal thyroid hormone function, and most are asymptomatic. However, massive enlargement can occur in which the gland extends around the pharynx or extends below the level of the thoracic inlet into the chest. In 1939 Crile described substernal goiters as those extending to the aortic arch. Recently In 2008, Huins et al. described, a three-tiered system derived from a large meta-analysis which classified substernal goiters in relation to the aortic arch, pericardium, and atrium.
Massive and substernal goiters are often technically demanding procedures, due to the gland’s vascularity and its proximity to the larynx, trachea, and the recurrent laryngeal nerves controlling vocal cord movement. In addition, the exposure needed to identify and preserve important structures is hampered when the goiter extends below the level of the thoracic inlet into the enclosed space of the chest. Nevertheless, even large goiters can usually be delivered out of the chest through an incision low in the neck using technical maneuvers. However, extension inferior to the aortic arch more often necessitates additional exposure.
Substernal goiters may come to clinical attention as a visible mass or as a result of goiter-related symptoms: a compressive pressure–type sensation, shortness of breath on lying down, and problems swallowing. Indeed, substernal goiters are more often symptomatic than massive goiters limited to the neck. Substernal goiters may not be visible on inspection because most of the gland is in the mediastinum ( Figs. 81.1 to 81.3 ). Patients develop symptoms due to cumulative growth within the confines of the thoracic inlet and chest cavity, compressing or displacing the trachea, esophagus, and mediastinal blood vessels. Enlargement is typically slow and progressive over many years. Sudden, rapid enlargement of a long-standing goiter suggests the development of cancer but could also be due to abrupt bleeding into the gland.
Surgery for goiter is the definitive treatment for massive or substernal goiter but is associated with a number of potential complications. The surgery is highly effective in ameliorating goiter-related symptoms, but diligent surgical execution is needed to optimize favorable outcomes. Strategies to limit intraoperative bleeding, enhance exposure, and facilitate atraumatic surgical dissection will diminish intraoperative complications.
Key Operative Learning Points
Assess the level of patient-reported symptoms, prior to surgery. Consider using a thyroid-specific tool, such as the short version of the thyroid-related patient-reported outcome (ThyPRO) tool prior to surgery; this tool may also be administered several months after surgery. Rapid enlargement associated with pain and dysphagia suggests the development of an aggressive malignancy.
Preoperative evaluation should include serum thyroid-stimulating hormone (TSH) and imaging. Both an ultrasound and a computer tomography (CT) scan should be obtained. The CT scan with intravenous contrast will determine the substernal extent of the goiter and its relationship with large blood vessels and identify posterior mediastinal extension associated with displacement of the recurrent laryngeal nerve. The appearance may also suggest the presence of an infiltrative malignancy that could alter the treatment plan.
Continuous laryngeal nerve monitoring that tests the functional integrity of the recurrent laryngeal nerve by means of continuous intraoperative vagal nerve stimulation is particularly useful in the management of large substernal goiters. During these cases the recurrent laryngeal nerve may not be readily identified because it is hidden behind a large obstructing goiter and subject to traction injury. Evidence for the use of continuous laryngeal nerve monitoring is mounting, but this technology does not yet represent standard of care.
Instrumentation used for minimally invasive thyroid surgery is useful in substernal goiter surgery, which usually requires dissection in narrow spaces with limited exposure; having the proper instrumentation may obviate the need for manubrium or sternal osteotomies, which may be required in revision cases or those involving substernal thyroid cancer ( Fig. 81.4 ).
History of present illness
History of anterior neck mass
Duration of mass, interval enlargement
Direct compression of the trachea or esophagus by a substernal goiter can cause dysphagia to solids, positional dyspnea, and dysphonia. Positional dyspnea and orthopnea are frequently associated with substernal goiter with tracheal compression on cross-sectional imaging.
History of snoring, daytime somnolence, sleep apnea
Factors predisposing to thyroid cancer, such as history of neck radiation, or family history of thyroid cancer
Past medical history
A complete past medical and surgical history must be obtained from the patient. Prior imaging and biopsies should be reviewed. A history of hypertension and prior neck surgery should be noted.
Respiratory distress? Stridor? Hoarseness?
Venous congestion of neck/facial venous collaterals
Size and location of the goiter
Consistency: Is the mass firm or hard?
Is it tethered to the overlying skin; is the skin indurated?
Does it extend to the clavicle?
Does it move with swallowing? Is the inferior extent palpable with swallowing?
Is the trachea palpable, and is it deviated?
World health organization (WHO) classification ( Table 81.1 ): Patients with goiters visible on casual inspection may have few goiter-related symptoms. Substernal goiters associated with patient symptoms may not necessarily be appreciated on clinical examination alone (see Fig. 81.1 ).
Palpable but invisible even in full extension
Palpable in neutral position/visible in extension
Visible no palpation required to make diagnosis
Visible at a distance
Palpable cervical lymphadenopathy and neck levels involved
Larynx: Examination of the larynx should also assess the pharynx for compression, as well as vocal cord mobility.
Pemberton maneuver: The maneuver is performed by having the patient raise both arms against the face for several minutes to see if the patient develops reversible facial flushing or cyanosis, sometimes associated with shortness of breath or stridor. A positive Pemberton sign indicates superior vena cava syndrome causing diminished venous outflow from and venous congestion of the head and neck due to goiter-related compression of the vessels in the mediastinum. Patients may also have enlargement of venous collaterals in the chest and neck.
Ultrasound of the neck
Prior to thyroidectomy, patients should undergo a formal ultrasound of the neck and thyroid gland to assess the risk of malignancy in the goiter. In the presence of abnormal adenopathy or invasive features, a fine-needle aspiration biopsy may be warranted.
CT of the neck/chest
A CT scan of the neck and chest is recommended if substernal extension is suspected. Evaluation of the caudal extent of the goiter will facilitate surgical planning and enable added thoracic exposure should it prove to be necessary.
Caudal growth of a goiter in the visceral space initially involves extension into the pretracheal space into the anterior mediastinum or retroesophageal extension into the posterior mediastinum. Significantly, posterior mediastinum extension is rare in the absence of concomitant anterior mediastinum involvement. Goiter extension into the posterior mediastinum suggests anterior displacement of the recurrent laryngeal nerve. A meta-analysis linked extension to specific structures with the need for additional procedures ( Table 81.2 ). Goiter extension above the fourth vertebrae or above the level of the aortic arch can usually be managed transcervically. Posterior mediastinum extension of the goiter necessitates a thoracotomy for exposure and extirpation.