Location of Parathyroid Glands during Thyroid Surgery: An Anatomical Study in a Surgical Series

Research Article

Annals Thyroid Res. 2014;1(1): 13-16.

Location of Parathyroid Glands during Thyroid Surgery: An Anatomical Study in a Surgical Series

Mohamed M and Sheahan P*

Department of Otolaryngology – Head & Neck Surgery, South Infirmary Victoria University Hospital, Ireland

*Corresponding author: Sheahan P, Department of Otolaryngology – Head & Neck Surgery, South Infirmary Victoria University Hospital, Cork, Ireland

Received: September 15, 2014; Accepted: October 17, 2014; Published: October 20, 2014

Abstract

Introduction: Performance of good thyroid surgery requires thorough knowledge location of parathyroid glands, in order to avoid inadvertent damage or resection leading to postoperative hypoparathyroidism. The purpose of the present study was to describe the location of normal parathyroid glands in our surgical series.

Methods: Prospective cohort study of 282 consecutive thyroid and parathyroid surgeries performed over a 2-year period by a single surgeon.

Results: The most common location for superior parathyroid glands was just above the Tubercle of Zuckerkandl, and the most common location for inferior parathyroid glands was superficially on the lateral surface of the thyroid. Inferior parathyroid gland locations demonstrated greater variability than that of superior glands. Just under one half of superior parathyroid glands and one quarter of inferior thyroid glands were related to the location of the Tubercle of Zuckerkandl.

Conclusion: The location of parathyroid glands in patients undergoing thyroid surgery shows significant variability. Awareness of possible locations of these glands is critical for the thyroid surgeon.

Keywords: Thyroidectomy; Parathyroid; Location; Anatomy

Abbreviation

RLN: Recurrent Laryngeal Nerve

Introduction

The number of thyroid operations performed has increased in recent years [1]. In experienced hands, major morbidity from thyroid surgery is uncommon. Perhaps the most common complication of thyroidectomy is postoperative hypocalcaemia. In most cases, postthyroidectomy hypocalcaemia is a temporary; however, permanent hypoparathyroidism may develop in a minority of patients [2,3].

Post-thyroidectomy hypocalcaemia arises due to postoperative hypoparathyroidism secondary to intraoperative trauma to parathyroid glands, disruption of parathyroid blood supply, or inadvertent parathyroid resection. To minimize the risk of these complications, a thorough knowledge of the anatomy of the thyroid and parathyroid glands is essential. In particular, awareness of the likely position of parathyroid glands is critical to avoid postoperative hypoparathyroidism.

Most individuals have 4 parathyroid glands, comprising one superior and one inferior gland on each side, although supernumerary parathyroids are believed to be present in 5% [4]. The superior parathyroid gland originates endoderm of the fourth branchial pouch, and migrates towards the developing gland with the lateral thyroid process (ultimobranchial body). The inferior parathyroid gland originates from the third branchial pouch and migrates caudally with the developing thymus gland [5]. The Tubercle of Zuckerkandl is a lateral projections from the thyroid, which is believed to represent remnants of the lateral thyroid process, and, when present, separates the parathyroid glands, with the superior gland always being located cephalad, and the inferior caudad [5]. When present, it serves as a useful landmark for the Recurrent Laryngeal Nerve (RLN), which it nearly always overlies in the vicinity of its extralaryngeal termination [6,7]. The thyrothymic ligament represents the remnants of the embryological path of descent of the thymus gland. When present, it may contain the inferior or supernumerary parathyroid glands [5].

The purpose of the present study was to describe the location of parathyroid glands in a series of patients undergoing thyroid or parathyroid surgery.

Methods

This was a prospective study of 282 consecutive thyroid and parathyroid surgeries performed by the senior author (PS) between May 2012 and September 2014. Exclusion criteria for the present study were cases which had gone previous thyroid or parathyroid surgery on the side ipsilateral to that being dissected. A prospective database was maintained into which anatomical, patient demographic, and other clinicopathological details were entered immediately after surgery.

The surgical technique employed in most cases in the present series was a capsular dissection technique, with reflection of parathyroid glands and / or parathyroid-containing tissue off the thyroid gland, without disruption of parathyroid blood supply. Parathyroid glands were “watched out for”, but if not readily identifiable, they were not systemically sought. We have shown that this technique does not lead to any increased risk of hypocalcaemia [2]. Criteria used to positively identify parathyroid glands were characteristic colour (caramel yellow-brown) and consistency (firm, well-defined, and non-friable), with or without colour change with devascularisation in certain cases. Positive identification of parathyroid was made only where the senior author was confident that parathyroid was unequivocally identified. Cases of “possible” parathyroids were considered to not have been positively identified.

The positions of parathyroid glands were free-texted into the prospective database just after surgery. For the purpose of the present study, these were grouped post-hoc into location categories. Inferior parathyroid glands were accordingly grouped into the following locations: (1) around or just caudad to the Tubercle of Zuckerkandl, or the expected position of the Tubercle of Zuckerkandl; (2) overlying the recurrent laryngeal nerve (RLN), caudad to the position of the Tubercle of Zuckerkandl; (3) deeply located on the lateral surface of the thyroid, caudad to the Tubercle of Zuckerkandl, and clear of the RLN; (4) superficially on the lateral surface of the thyroid; (5) deeply located, near to but clear of the lower surface of the thyroid, in paratracheal tissue; (6) in the thyrothymic ligament; (7) in the superior mediastinum (Figure 1). Location of superior parathyroid glands were grouped as follows: (1) around or just cranial to the Tubercle of Zuckerkandl, or the expected position of theTubercle of Zuckerkandl; (2) just overlying or otherwise closely associated with the termination of the RLN; (3) low down on the deep surface of the superior pole, medial to the RLN, usually only encountered during dissection of the Tubercle of Zuckerkandl and cricotracheal region; (4) on the deep surface of the superior pole, encountered during mobilization of the superior pole from above, prior to dissection in the cricotracheal region; and (5) near to but clear of the deep surface of the superior thyroid pole (Figure 2).