ABSTRACT
Introduction: Terminal branches of inferior thyroid artery (ITA) supplies thyroid and parathyroids. Recurrentlaryngeal nerve (RLN) is related to ITA at lower pole of thyroid and RLN may lie either posterior, anterior orintermingled with terminal branches of ITA. RLN is a vulnerable structure that gets damaged during thyroidsurgeries.Aim: Present study aims to determine variation in relationship between ITA and RLN, entering pattern of ITA intothyroid and number of terminal branches of ITA in Sri Lankan population.Materials and methods: A total of 312 sides (Male:204, Female:108) of thyroid together with intact neurovascularstructures were selected for study of relationship, entrance pattern and number of terminal branches of ITA. TheRLN may lie either posterior (Type A) or anterior (Type B) to ITA or its branches. Sometimes RLN may interminglewith terminal branches of ITA (Type C).Results: A total sample of 65.2% in male (M) and 60.9% in female (F) were Type A, samples of 10.35%(M) and22.22%(F) were Type B and 24.5%(M) and 17.59%(F) were type C. Type A was more predominant in left side of bothgenders and in the right side there are 50% of chances for Type A in both genders. Comparatively Type B was morein female and Type C was more in male. A total of 63.7%(M) and 69.44%(F) ITA entered into middle 1/3rd, 36.27%(M)and 30.55%(F) into lower 1/3rd of the thyroid lobe and entering pattern was more or less similar in both genders.ITA commonly entered thyroid just above junction of middle and lower third of thyroid lobe. ITA divided into twobranches in 52.45%9(M) and 56.48%(F), three in 44.6%(M) and 41.66%(F) and four in 2.94%(M) and 1.85%(F) ofstudied samples.Conclusions: Knowledge of anatomical variation of ITA and RLN is mandatory to avoid injury to RLN in thyroidsurgeries. Understanding the entrance pattern and terminal branches of ITA are essential for thyroid andparathyroid surgeries