Overview
Definition:
Mediastinal goiter refers to an enlarged thyroid gland that extends into the mediastinum, typically the superior mediastinum
The vast majority (over 90%) are extensions of a cervical goiter, rather than primary mediastinal thyroid tissue.
Epidemiology:
Most common cause of a superior mediastinal mass
Occurs predominantly in women, particularly in iodine-deficient regions
Incidence is higher in older age groups, though can occur in younger patients.
Clinical Significance:
Can lead to significant morbidity due to tracheal or esophageal compression, or vascular compromise
Early recognition and appropriate surgical management are crucial for patient outcomes and to prevent potentially life-threatening complications.
Indications
Absolute Indications:
Symptomatic compression (dyspnea, dysphagia, hoarseness)
Airway compromise requiring intervention
Suspected malignancy or follicular carcinoma arising from the goiter
Rapidly growing goiter
Substernal extension not amenable to conservative management.
Relative Indications:
Cosmetic concerns
Prophylactic removal in asymptomatic patients with significant substernal extension or high-risk factors for future symptoms
Management of toxic multinodular goiter with substernal extension.
Contraindications:
Generally few absolute contraindications to sternotomy for symptomatic mediastinal goiter
Relative contraindications include severe comorbidities that make any major surgery prohibitive, or a clearly benign, asymptomatic, small substernal extension where risks outweigh benefits.
Preoperative Preparation
History And Physical Examination:
Thorough history focusing on respiratory, swallowing, and vocal symptoms
Physical exam to assess for tracheal deviation, palpable masses in neck, and signs of venous engorgement
Assess for symptoms of thyrotoxicosis or hypothyroidism.
Imaging Studies:
CT scan of the neck and chest with contrast is essential to delineate the extent of the goiter, its relationship to adjacent structures (trachea, esophagus, great vessels), and identify any intrathoracic extension
Thyroid ultrasound can assess cervical component and vascularity
MRI may be used in specific cases.
Laboratory Investigations:
Thyroid function tests (TSH, Free T4, Free T3) to assess thyroid status
Parathyroid hormone levels if manipulation of parathyroids is anticipated
Complete blood count, electrolytes, renal and liver function tests, coagulation profile are standard for surgical risk assessment.
Anesthesia Considerations:
Close collaboration with anesthesiology is critical
Awake fiberoptic intubation may be required for severe airway compromise
Careful positioning to avoid undue pressure on the airway
Monitoring invasive arterial pressure and central venous pressure may be necessary.
Surgical Management
Approach Selection:
Sternotomy (median sternotomy) is the preferred approach for large substernal goiters, those extending deep into the mediastinum, or those with significant mediastinal involvement
A cervical collar incision alone may suffice for smaller, superiorly extending goiters.
Procedure Steps Sternotomy:
Median sternotomy is performed
The mediastinum is carefully dissected, identifying the goiter capsule and its relationship to the trachea, esophagus, recurrent laryngeal nerves, and great vessels
Careful mobilization of the thyroid gland from its surrounding structures is performed
Blunt and sharp dissection techniques are employed
The goiter is then delivered superiorly through the sternotomy
Careful attention is paid to hemostasis and the preservation of parathyroid glands and recurrent laryngeal nerves
Thyroid lobectomy or total thyroidectomy is performed based on the extent and pathology
If the goiter is truly large and adherent, en-bloc resection with surrounding tissues might be considered but is rare.
Nerve Preservation:
Identification and preservation of both recurrent laryngeal nerves are paramount
This often requires meticulous dissection within the tracheoesophageal groove
Similarly, careful identification and preservation of parathyroid glands are essential to avoid postoperative hypoparathyroidism.
Hemostasis And Drainage:
Meticulous hemostasis is achieved
Chest tubes may be placed if significant pleural dissection or extensive mediastinal work is performed
Drains are typically placed in the mediastinum
The sternum is closed with sternal wires.
Postoperative Care
Monitoring:
Close monitoring of airway patency, breathing, and hemodynamics
Vigilance for signs of recurrent laryngeal nerve injury (vocal cord dysfunction), hypocalcemia, and bleeding
Chest tube and drain management.
Pain Management:
Adequate pain control with analgesics is important for patient comfort and facilitating deep breathing exercises.
Endocrine Management:
Postoperative thyroid hormone replacement is usually initiated, especially after total thyroidectomy
Calcium levels are monitored closely, and calcium/vitamin D supplementation is administered if hypocalcemia develops.
Mobilization And Respiratory Care:
Early mobilization and incentive spirometry are encouraged to prevent pulmonary complications like atelectasis and pneumonia.
Complications
Early Complications:
Bleeding and hematoma formation requiring re-exploration
Recurrent laryngeal nerve injury leading to vocal cord paralysis (unilateral or bilateral)
Hypoparathyroidism causing hypocalcemia
Airway obstruction due to edema or bilateral vocal cord paralysis
Wound infection
Pneumonia.
Late Complications:
Persistent hypoparathyroidism requiring long-term calcium supplementation
Recurrent goiter formation
Scarring
Esophageal or tracheal stenosis (rare).
Prevention Strategies:
Meticulous surgical technique with careful identification and preservation of recurrent laryngeal nerves and parathyroid glands
Adequate hemostasis
Prophylactic calcium and vitamin D in high-risk patients
Aggressive respiratory physiotherapy
Judicious use of drains and antibiotics.
Prognosis
Factors Affecting Prognosis:
The prognosis for mediastinal goiter treated with sternotomy is generally excellent
Factors influencing outcome include the degree of airway compression preoperatively, presence of malignancy, and operative complications such as recurrent laryngeal nerve injury or hypoparathyroidism.
Outcomes:
Most patients experience significant symptomatic relief after successful surgical resection
Long-term survival is high, especially in the absence of malignancy
Careful follow-up is essential to monitor for recurrence or endocrine dysfunction.
Follow Up:
Regular follow-up appointments with endocrine and surgical teams
Thyroid function tests and neck palpation are performed periodically
Imaging may be required if symptoms of recurrence arise
Patients on thyroid hormone replacement need lifelong monitoring.
Key Points
Exam Focus:
Understand indications for sternotomy vs
cervical approach
Recognize anatomical structures at risk (RLN, parathyroids, great vessels)
Differentiate benign vs
malignant mediastinal masses
Management of postoperative hypocalcemia and vocal cord dysfunction.
Clinical Pearls:
CT scan is king for defining mediastinal goiter extent
Always consider the possibility of malignant transformation
Preserving parathyroids is crucial
autotransplantation may be considered if accidental removal is unavoidable
Secure the airway first
Never dissect blindly in the superior mediastinum.
Common Mistakes:
Inadequate preoperative imaging leading to unexpected surgical challenges
Failure to identify and preserve recurrent laryngeal nerves
Mistaking a substernal goiter for a primary mediastinal tumor on imaging
Inadequate postoperative monitoring for hypocalcemia or airway issues.