Abstract:
Introduction: Terminal branches of inferior thyroid artery (ITA) supplies thyroid and parathyroids. Recurrent
laryngeal nerve (RLN) is related to ITA at lower pole of thyroid and RLN may lie either posterior, anterior or
intermingled with terminal branches of ITA. RLN is a vulnerable structure that gets damaged during thyroid
surgeries.
Aim: Present study aims to determine variation in relationship between ITA and RLN, entering pattern of ITA into
thyroid 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 neurovascular
structures were selected for study of relationship, entrance pattern and number of terminal branches of ITA. The
RLN may lie either posterior (Type A) or anterior (Type B) to ITA or its branches. Sometimes RLN may intermingle
with 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) and
22.22%(F) were Type B and 24.5%(M) and 17.59%(F) were type C. Type A was more predominant in left side of both
genders and in the right side there are 50% of chances for Type A in both genders. Comparatively Type B was more
in 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 two
branches 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) of
studied samples.
Conclusions: Knowledge of anatomical variation of ITA and RLN is mandatory to avoid injury to RLN in thyroid
surgeries. Understanding the entrance pattern and terminal branches of ITA are essential for thyroid and
parathyroid surgeries.
