Embryological Remnants of the Thyroid Gland and their Significance in Thyroidectomy

Abstract

Embryological Remnants of the Thyroid and Their Significance in Thyroidectomy Prof Ranil Fernando The Thyroid gland develops from the floor of the primitive pharynx & parts of the ultimobranchial body and descends into the anterior triangles of the neck. It is functional around the 7th week of gestation. There are anomalies associated with the embryological development which give rise to recognizable clinical disease in patients. The Thyroid gland may be absent, fail to descend, remnants of descent left in the neck or the thyroid gland may descend too far. All these are well recognized clinical entities. In addition, there are three (3) significant embryological components which are well recognized and need to be identified and removed during Thyroidectomy. These are the Pyramidal lobe, Tubercle of Zuckerkandl, and the Thyrothymic remnants. It is important to carefully dissect and identify these embryological remnants not only to prevent recurrence, but also because these are in close proximity to important structures such as the recurrent laryngeal Nerve and parathyroid gland and they assist the surgeon in identifying these important anatomical structure that need preservation. Recurrent goitres are mainly due to the embryological remnants left behind especially in the subtotal thyroidectomy era. These recurrences can isolated or occur in combination. Commonly recurrence from all three remnants is found. In our experience the Pyramidal lobe recurrences and tubercle of Zuckerkandl are found in about 50- 60% of the patients and the Thyrothymic remnants are found in about 30- 40 % of the patients Surgery for recurrent disease is fraught with danger and a sound knowledge of embryological remnants will enable an experienced surgeon to undertake redo thyroid surgery safely.