*1.2. Postoperative Hypoparathyroidism*

Transient hypoparathyroidism has been reported in up to 20% of patients undergoing total thyroidectomy for thyroid cancer, with permanent hypoparathyroidism reported in up to 3% [32]. Transient hypoparathyroidism has been reported in up to 26.2% for cases of medullary thyroid carcinoma, with a clear association existing between the extent of lymph node dissection and the observation of four PGs [33]. A systematic review and meta-analysis on bilateral thyroid surgery demonstrated an even higher median rate of transient (27%, interquartile range—IQR: 19–38%) and permanent (1%, interquartile range—IQR: 0–3%) hypocalcemia [34]. The rates increase with the extent of surgery, with symptomatic hypoparathyroidism complications arising in 28.7% of thyroid cancer surgeries (28.4% temporary, 0.3% permanent), as reported from a single center [5]. The permanent hypoparathyroidism rate is reported as 0.4–13.8% [31] and can reach 37% in bilateral neck dissection for thyroid cancer [35].

Although the vast majority of postoperative hypoparathyroidism cases are transient and resolve within 6 months of surgery, a small percentage of patients require calcium and vitamin D supplementation for the rest of their lives. This situation is considered serious and negatively affects quality of life [5]. Women are significantly more likely than men to require permanent calcium replacement for postoperative hypoparathyroidism [36]. Consequently, women of child-bearing age require close monitoring during pregnancy, as they are at risk of hyper- and hypocalcemia. As both conditions have consequences to the fetus and the mother, calcium dose adjustments are frequent [37]. Other implications of postoperative hypoparathyroidism include the economic costs of prolonged hospital stay, additional investigations, procurement of medications, the medical burden associated with lifetime medication, and routine hospital visits for follow-ups. Moreover, there are considerable disease burdens related to chronic kidney failure, increased psychiatric complaints, and basal ganglia calcification, among other sequelae, and possible increases in mortality [38,39].

Surgical techniques that improve the preservation of the PGs and their blood supply are greatly needed. The present review highlights the utility of one such innovation, i.e., fluorescence imaging, in preserving the PGs during total or near-total thyroid resection ± lymph node dissection in the case of thyroid cancer.

The purpose of this review is to provide evidence on the utility of fluorescence-guided surgery for preserving the PGs and preventing hypoparathyroidism, with a particular focus on thyroid cancer surgery. The specific objectives of this review are (A) to determine the utility of the different fluorescence imaging techniques in preventing hypoparathyroidism as a complication of thyroid surgery; (B) to determine the feasibility of FIGS in thyroid cancer surgery, with an emphasis on ease of use, added surgical time, and complications related to the technique; and (C) to identify future directions in the use of fluorescence imaging to prevent postoperative hypoparathyroidism.
