While reading in the literature about new advances in knowledge and surgical techniques, it is often easy to lose track of the longstanding knowledge that we all acquired during our training. This is why this article on the anatomy and embryology of the parathyroid gland is a real pleasure to read as it re-visits the information we were all taught years ago but yet somehow may have lost a little on the way – myself at least! The clinical application of this knowledge is considerable, especially when trying to identify the offending adenoma when the ‘usual sites’ have been exhausted. The article includes line drawings to aid anatomical understanding of where ectopic glands may reside.
Some interesting points have been included herewith. Mirror image symmetry between the two sides has been cited as 80% for the superior and 70% for the inferior glands. There may also be more than four glands (25%) or less than four glands (6%), the supernumery ones often being smaller and located near to the normal glands, mediastinum or thymus. Superior parathyroid adenomas on the right side have been found to be abutting the RLN in just under 50% of cases, with the average overall distance from the nerve being 0.25cm.
Other adenomas were more distant but this is a useful fact when dissecting a right superior adenoma and can aid more careful counselling preoperatively. Ectopic locations of superior glands include the tracheoesophageal groove, posterior mediastinum, retro-oesophageal, and retropharyngeal positions in the carotid sheath or intrathyroidal locations. Occasionally thought to be above the superior pole of the thyroid in 1%. The inferior gland tends to lie superficial to the RLN (cf. superior glands are deep to RLN) and have a much greater area of variability as per the embryology.
