Serin Peter1 , Raniprabha Sukumaran2
BACKGROUND The inferior thyroid artery is an important artery arising from the thyrocervical trunk. It provides the main arterial supply to the parathyroids along with the lower half of the thyroid gland. It is also believed to be responsible for thyroid perfusion during the foetal development. The inferior thyroid artery is known for its anatomical variations. High variations in the inferior thyroid artery may result in unnecessary morbidity during the operative procedures involving those areas. So a proper knowledge of the variations and relations of the artery with the surrounding anatomical structures mainly recurrent laryngeal nerve, is a surgeon`s best defence in preventing an iatrogenic injury to the artery and nerve. Injury to the recurrent laryngeal nerve paralyses muscles of larynx thereby causing problems with phonation and respiration. We wanted to study the variations in the origin, course, and branches of the inferior thyroid artery particularly with the recurrent laryngeal nerve. METHODS This study was conducted in the Department of Anatomy, Kottayam Medical College by dissection of 50 embalmed cadavers following routine dissection methods. The specimens were obtained after ethical clearance. The inferior thyroid artery was carefully dissected out, its origin, course and relations with recurrent laryngeal nerve were documented and pictures taken. RESULTS On the right side of 46 (92 %) of the 50 specimens, the inferior thyroid artery was seen originating from thyrocervical artery and in the remaining 4 (8 %), directly from the subclavian artery. On the left side, the artery originated from thyrocervical trunk in 45 (90 %) specimens and from the main subclavian artery in 5 (10 %) specimens. On the right side, in 30 specimens (60 %), the nerve passed anterior to the artery, in 14 (28 %) the nerve passed behind the artery and in the remaining 6 (12 %) specimens, in-between the branches of the artery. The nerve passed behind the artery in 32 (64 %) specimens, in front of the artery in 16 (32 %) and in between the branches of the artery in 2 (4 %) specimens on the left side. In 49 specimens (98 %) the artery passed in front of the vertebral artery which is the normal course but in 1 specimen (2 %), the inferior thyroid artery passed behind vertebral artery this being a rare finding. CONCLUSIONS Inferior thyroid artery is one of the main culprits of massive bleeding during thyroidectomy. Its importance also increases due to the fact that it is the main artery supplying the parathyroids. The recurrent laryngeal nerve is frequently injured when there is an anomalous course of the inferior thyroid artery. It is a frequent site for thyrocervical trunk aneurysms too and its relation to the vertebral artery gains importance there. A good knowledge of the variations in its origin, course and branching is therefore very essential for the surgeon in preventing an iatrogenic injury.
