|Year : 2016 | Volume
| Issue : 1 | Page : 95-97
Variant arterial supply of thyroid gland
Angel, Anjali Jain
Department of Anatomy, Christian Medical College, Ludhiana, Punjab, India
|Date of Web Publication||22-Dec-2015|
Department of Anatomy, Christian Medical College, Ludhiana, Punjab
Source of Support: None, Conflict of Interest: None
The thyroid gland is a highly vascular gland placed anteriorly in the neck and is supplied by the superior thyroid artery (STA), inferior thyroid artery (ITA), and sometimes the thyroidea ima artery. During the routine dissection for undergraduate students, variations in the arterial supply of thyroid gland were observed. The thyroid gland showed a lobulated appearance. On the left side, STA was found to be absent. However, two ITA were observed on the same side. These supplied the gland from its posterior surface. The knowledge of variations in vascularity of the thyroid gland is important in procedures such as emergency cricothyroidectomy, radical neck dissection, catheterization, reconstruction of aneurysms, and carotid endarterectomy.
Keywords: Absent superior thyroid artery, accessory inferior thyroid artery, thyroid Gland
|How to cite this article:|
Angel, Jain A. Variant arterial supply of thyroid gland. CHRISMED J Health Res 2016;3:95-7
| Introduction|| |
The thyroid gland is a highly vascular gland placed anteriorly in the neck, extending from the level of fifth cervical vertebra to first thoracic vertebra. The lobes of gland are conical. Their apices diverge laterally to the oblique line on the lamina of thyroid cartilage, and their bases are at the level of 4th or 5th tracheal ring. The gland is supplied by the superior thyroid artery (STA) and inferior thyroid artery (ITA), and sometimes the thyroidea ima artery (a branch from brachiocephalic trunk or arch of aorta) [Figure 1].
|Figure 1: Typical pattern of superior thyroid artery and lobulated appearance of thyroid gland|
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The STA is the first branch of external carotid artery, and arises from its anterior surface just below the level of greater cornua of hyoid bone. It is closely related to external laryngeal nerve. It pierces the thyroid fascia and then divides into anterior branches (at the apex of the lobe) and supplies lateral and medial surfaces of the lobes of the thyroid gland. STA follows a more reliable course and is rarely absent. It is the dominant arterial supply of the thyroid gland, upper larynx, and neck region.
The ITA is a branch from thyrocervical trunk, which in turn is the branch from subclavian artery. It approaches the base of the thyroid gland, and divides into superior and inferior branches to supply inferior and posterior surfaces of the gland. It also vascularises parathyroid glands, pharynx, larynx, and esophagus. In contrast to STA, the ITA may vary considerably.
The anatomy of thyroid gland is relevant to both clinicians and surgeons. A profound anatomical insight into variations of vessels in the region is important in carrying out procedures such as neck dissection, thyroid resections, and tracheostomies., Atypical branching pattern of vessels causes intraoperative bleeding and postoperative hematoma. An injury to ITA also leads to ischemia of the parathyroid gland leading to hypoparathyroidism.
However, seldom is such variation in arterial supply mentioned in the textbooks.
| Case Report|| |
During the routine dissection for undergraduate students in the Department of Anatomy, variations in the arterial supply of thyroid gland were observed. The thyroid gland showed lobulated appearance [Figure 2]. On the left side, STA was found to be absent. However, two ITA were observed on the same side. Both the ITA originated from thyrocervical trunk close to each other. These supplied the gland from its posterior surface on the right side, both STA and ITA showed a typical pattern.
|Figure 2: Absent superior thyroid artery. ECA: External carotid artery, CCA: Common carotid artery, TCT: Thyrocervical trunk. (1) Inferior thyroid artery, (2) accessory inferior thyroid artery|
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| Discussion|| |
The knowledge of variations in vascularity of thyroid gland is important in procedures such as emergency cricothyroidectomy, radical neck dissection, catheterization, reconstruction of aneurysms, and carotid endarterectomy. The lowest incidence of arterial anomalies of thyroid gland have been reported in Swiss population and the highest in Americans. However there is a paucity of literature, with regard to anomalous arterial supply of thyroid gland in Asian subcontinent.
Moriggl and Sturm reported a case, where both STA and ITA was absent on the left side. The gland on the left was supplied by thyroidea ima artery.
Sedy reported an incidental finding of an accessory ITA on the right side. Both the ITA arose separately from thyrocervical trunk. On the left side, only one ITA was observed, and STA showed normal morphology.
In a case reported by Doll an accessory, ITA was identified on the right side, which originated from thyrocervical trunk. The ITA on left side and STA on both sides showed usual pattern.
Mehta et al. observed that the right STA was absent. The ITA, however, showed typical pattern.
The present case is a unique variation as an accessory ITA and an absent STA were observed on the same side. Such a variation has not been reported previously in literature.
The possible ontogenic explanation for the present anomaly could be persistence of retiform vascular system in connection with common carotid artery. These persistent channels supplement or substitute regular arteries; thereby ensuring an ample blood supply to that side of thyroid gland, which is devoid of regular vessels.
This is the possible explanation of accessory ITA on the side, where STA was absent.
It seems reasonable to propose that a surgical approach for procedures in the neck must be exercised with extreme caution in the presence of such arterial variations. During thyroidectomy or parathyroidectomy, the ITA must be ligated carefully avoiding injury to recurrent laryngeal nerve, so as to spare vocal cord paralysis.
Therefore, variations in the arterial supply of thyroid gland deserve a special mention in anatomical, radiological, and surgical studies.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]