Anatomical Variations in the Origin of Superior Thyroid Artery and its Relation with External Laryngeal Nerve and their Clinical Importance-A Cadaveric Study

The major arterial supply of thyroid gland is from superior and inferior thyroid arteries. The superior thyroid artery (STA) usually arises from the external carotid artery. The external laryngeal nerve runs in close proximity to the origin of the superior thyroid artery later leaves the artery by turning medially above or below the upper pole of the thyroid gland.   MATERIAL AND METHODS A descriptive study was undertaken on 20 embalmed cadavers. The anterior triangle of neck was dissected bilaterally. The site of origin of STA level of origin in relation to the upper border of lamina of thyroid cartilage and relation of the STA with external laryngeal nerve were observed and noted.   RESULTS The STA arises from the external carotid artery in 27.5%, common carotid artery in 62.5%, common carotid bifurcation in 5% and arises by a common trunk with lingual artery at common carotid bifurcation in 5%. The distance from the upper pole to the point where external laryngeal nerve turns medially is more than 10 mm in 50%, less than 10 mm in 25% and 10 mm in 25%.   CONCLUSION The variations in the pattern of origin of the superior thyroid artery and its relation to external laryngeal nerve is a very common phenomenon. The head and neck surgeons must be aware of all possible variations to avoid postoperative complications and legal issues.