A 40-year-old woman undergoes total thyroidectomy for a 1.5 cm papillary thyroid carcinoma (classical variant, unifocal, intrathyroidal, node-negative). Post-operatively, she develops perioral tingling and Chvostek's sign on day 2. Which intraoperative parathyroid gland injury mechanism best explains transient hypocalcaemia in this scenario?
- A Inadvertent excision of all four parathyroid glands
- B Devascularisation of parathyroid glands with preservation in situ ✓
- C Injury to the external branch of the superior laryngeal nerve
- D Hypomagnesaemia impairing PTH release
Explanation
The most common cause of transient post-thyroidectomy hypocalcaemia is devascularisation (disruption of the small terminal branches of the inferior thyroid artery supplying the parathyroid glands) rather than inadvertent excision. Glands preserved in situ but devascularised have temporary dysfunction leading to transient hypoparathyroidism, usually resolving in days to weeks. Inadvertent excision of all four glands causes permanent hypoparathyroidism. Injury to the external branch of the SLN affects the cricothyroid muscle causing a voice pitch change, not hypocalcaemia.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.