Tubercle of Zuckerkandl

Introduction

Embryological Basis

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 1, p. 653
• Fischer's Mastery of Surgery, 8th Ed., p. 1061

Anatomy

• It is a lateral or posterior projection arising from the middle third of the thyroid lobe, typically on the posteromedial aspect.
• It can be identified in up to 60% of surgical dissections.
• Size varies from a small nodule to a large process that may mimic a thyroid nodule or goitre.
• When enlarged, it develops into a nodular process and can obscure critical structures.

Grading (Pelizzo's Classification)

Surgical Significance (the classic "THREEFOLD" importance)

1. Relationship with the Recurrent Laryngeal Nerve (RLN)

• The RLN most often runs medial to the tubercle of Zuckerkandl.
• The tubercle is encountered during fine dissection of the RLN as "the nerve usually tunnels underneath it" (Fischer's, p. 1074).
• The RLN may lie anterior, posterior, or in the substance of the ligament of Berry in this region.
• When the tubercle is enlarged, the RLN runs in a fissure medial to it - failing to recognize this leads to RLN injury.
• The RLN and its intersection with the inferior thyroid artery are most consistently identified near the cricoid cartilage in the vicinity of the ligament of Berry and the tubercle of Zuckerkandl - making the TZ a reliable surgical landmark for RLN identification.
• In 3-5% cases, the RLN may pass lateral to an enlarged tubercle - variation that must be anticipated.

2. Relationship with the Superior Parathyroid Gland

• The superior parathyroid gland is usually attached to the cranial aspect of the tubercle of Zuckerkandl.
• This consistent relationship makes the TZ an important landmark for parathyroid identification and preservation during thyroidectomy.
• The superior parathyroid lies between the TZ and the posterior capsule of the thyroid in most cases.
• Understanding this relationship prevents inadvertent devascularization or excision of the superior parathyroid.

3. Risk of Leaving Residual Thyroid Tissue

• When enlarged as part of a goitre, a significant portion of thyroid tissue may be inadvertently left behind if subtotal thyroidectomy is performed without recognizing the TZ.
• In substernal goitre, thyroid tissue may extend inferiorly from the TZ on either side of the neck, requiring particular attention to ensure complete resection and RLN protection.

Relationship with the Ligament of Berry

• The TZ is closely associated with the ligament of Berry (suspensory ligament of the thyroid / lateral ligament), which connects the thyroid to the trachea just below the cricoid cartilage.
• The RLN traverses the ligament of Berry and may lie anterior, posterior, or within the ligament itself.
• The TZ sits just lateral to the ligament of Berry and acts as a guide to the ligament and the nerve in this critical zone.

Clinical Relevance - Goitre Surgery

• In multinodular goitre, the TZ may enlarge dramatically and descend retrosternally.
• A missed TZ during subtotal thyroidectomy is a common cause of recurrent goitre - the residual TZ tissue regrows.
• In Graves' disease surgery, failure to remove the TZ leaves active thyroid tissue behind, risking recurrence.

Relationship to Parafollicular C-Cells

• Since the TZ represents the fusion zone with the ultimobranchial body, it is the richest region for parafollicular C-cells.
• This is clinically relevant in medullary thyroid carcinoma (MTC), which arises from C-cells - MTC tends to be most prominent in the upper-posterior thyroid where C-cells concentrate (around the TZ zone).

Summary Table

Sources

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 1, pp. 653-654
• Fischer's Mastery of Surgery, 8th Ed., pp. 1060-1074
• Mulholland and Greenfield's Surgery: Scientific Principles and Practice, 7th Ed., p. 4022