Problem
Revision or reoperative thyroid surgery is often technically challenging because of anatomic changes following primary surgery.
Presentation
Most thyroid cancers are differentiated, slow-growing, easily treatable tumors with an excellent prognosis after surgical resection and targeted medical therapy. Approximately one third of patients with differentiated thyroid cancer (DTC) have tumor recurrence; most are diagnosed within 10 years of treatment. [1, 2, 3] Locoregional recurrences may arise in the central or lateral neck, thyroid remnant, mediastinum, or, rarely, in the trachea or the muscle overlying the thyroid bed. The mortality from locally recurrent disease in the low-risk group (according to the Age, Metastases, Extent, and Size [AMES] prognostic index) with DTC is 4%. However, patients who are male and older than age 45 years experience a mortality rate of 27% once DTC recurs. [4]
Clinical or radiologic evidence of locally recurrent DTC is generally treated with surgical removal of the focus of disease and postoperative iodine-131 (131 I).
Indications
Reoperative thyroid surgery may be performed under a number of circumstances. A patient may have had a previous thyroid lobectomy and require a completion thyroidectomy for differentiated thyroid cancer (DTC). Recurrence of thyroid cancer may require reexploration of the thyroid bed or cervical lymph node dissection, including the central compartment (level VI). Additionally, occurrence of cancer in the thyroid remnant after operation for benign thyroid diseases or symptomatic disease in a partially removed nodular or multinodular goiter may also require reoperation. [5]
Relevant Anatomy
Normal anatomy
The thyroid is a highly vascular gland in the neck that overlies the proximal trachea and thyroid cartilage. It is composed of right and left lateral lobes joined at their medial aspects by an isthmus (see image below). In approximately 50% of patients, an appendage to the gland (termed the pyramidal lobe) courses cephalad from the isthmus. The strap muscles overlie the thyroid lobes.
The arterial blood supply to the gland is composed of the superior thyroid artery and the inferior thyroid artery, branches of the external carotid artery and the thyrocervical trunk, respectively (see the first image below). Approximately 3% of individuals also have a thyroid ima artery that supplies the gland. The thyroid is attached to the trachea by the ligament of Berry. The recurrent laryngeal nerves (RLN) are in close proximity to the thyroid as they course from the tracheoesophageal groove to the cricothyroid membrane. The tubercle of Zuckerkandl is an important landmark of the RLN. [6] The parathyroid glands lie in close proximity to the thyroid, usually as paired structures adjacent to the upper and lower poles of the thyroid gland (see the second image below).
Anatomical changes following thyroidectomy
Changes in cervical anatomy may take place following thyroidectomy. The carotid sheath is an important landmark in thyroid surgery. It provides the lateral boundary of dissection and is an important landmark when initially identifying the RLN. [7] Realizing that the great vessels of the neck may medialize following thyroidectomy and may be directly adjacent to the trachea (see the image below) is important. Scarring and fibrosis from prior surgery may cause increased difficulty in identifying and dissecting important structures. When reoperating the area of the ipsilateral thyroid remnant, the recurrent laryngeal nerve is often difficult to identify and dissect because it is buried in scar tissue. The tracheoesophageal groove itself may be scarred and distorted.
Axial CT scan of a patient one year after total thyroidectomy. The great vessels of the neck are significantly medialized.
For more information about the relevant anatomy, see Thyroid Anatomy.
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Axial CT scan of a patient with a thyroid lesion prior to thyroidectomy.
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Axial CT scan of a patient one year after total thyroidectomy. The great vessels of the neck are significantly medialized.
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Central compartment dissections in the previously operated neck. The recurrent laryngeal nerve (arrow) was traced out from the scarred tracheoesophageal groove.
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Revision neck dissection. Structures encountered that resemble a parathyroid should undergo frozen section biopsy. Exposed tissue adjacent to the great vessels was found to be metastatic papillary thyroid cancer.
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Thyroid gland, anterior and lateral views.
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Distribution of thyroid arteries with associated laryngeal nerve, anterior view.
