Rare variations in vascular pattern of thyroid gland

Introduction The thyroid gland, is placed anteriorly in the lower neck, level with the fifth cervical to the first thoracic vertebrae. Ensheathed by the pretracheal fascia, the gland consists of two lateral conical lobes connected by a narrow median isthmus. Each lobe measures 5 cm long, its greatest transverse and anteroposterior extents being 3 cm and 2 cm, respectively. The isthmus connects the lobe’s lower parts; it measures 1.25 cm transversely and vertically, and is usually anterior to the second and third tracheal cartilages, though often higher or sometimes lower because its site and size vary greatly. Occasionally, the isthmus may be absent [1]. The superior thyroid arteries anastomose along its upper border; at the lower border the inferior thyroid veins leave the gland. The superior thyroid artery (STA) is a branch arising from front of external carotid artery, gives glandular branches which on reaching the superior pole of the gland divide into anterior and posterior branches. The anterior branch accompanies the medial border of lateral lobe and anastomoses with its fellow of opposite side along the upper border of the isthmus of the gland. The posterior branch passes downward along the posterior border of lateral lobe and anastomoses with the ascending branch of inferior thyroid artery. The superior thyroid artery supplies the capsule and the connective tissue of the gland. The inferior thyroid artery a branch from thyrocervical trunk penetrates the deep surface of the gland and supplies the parenchyma of the gland. The gland is also supplied by numerous accessory thyroid arteries and occasionally by arteria thyroidea ima.