Fluorescent tool may help to protect parathyroid glands during surgery

Fewer hypoparathyroidism cases after a thyroidectomy reported in study

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

Share this article:

Share article via email
An illustration of a dashboard of risk level.

Using near-infrared autofluorescence (NIRAF) to protect the parathyroid glands during thyroid surgery did not significantly lower the risk of hypoparathyroidism as a surgical complication, a study with experienced thyroid surgeons reported.

Although there were fewer hypoparathyroidism cases with NIRAF three months after surgery, differences  were not statistically significant when compared with surgeries not using this tool.

Regardless of these findings, according to the researchers, NIRAF imaging appears to be of value in detecting the parathyroid glands and may be of benefit during complicated thyroid surgery.

The imaging study,” Effect of near infrared autofluorescence guided total thyroidectomy on postoperative hypoparathyroidism: a randomized clinical trial,” was published in the European Archives of Oto-Rhino-Laryngology.

Recommended Reading
A person is seen taking a sip of a drink while their kidneys are highlighted and enlarged to the sides.

Abnormal Calcium Levels Tied to Chronic Kidney Disease: Study

Damage to parathyroid glands common complication of thyroid surgery

Parathyroid hormone (PTH) — the most important regulator of calcium and phosphorus levels in the bloodstream — is produced by four small parathyroid glands in the neck.

Avoiding these glands during surgery to remove the thyroid gland can be challenging because they are located next to the thyroid gland and resemble thyroid tissue, lymph nodes, or fat. Damage to the parathyroid glands, resulting in abnormally low levels of PTH, or hypoparathyroidism, is the most frequent complication of thyroid surgery.

NIRAF exposes the parathyroid glands to near-infrared light, generating a unique fluorescent signal that helps distinguish them from surrounding tissue. While some studies suggest NIRAF during thyroid surgery can lower the risk of postoperative hypoparathyroidism, others indicate no difference when the imaging technique was applied.

Researchers in Demark conducted a controlled clinical trial (NCT04193332) to further investigate whether NIRAF during thyroid surgery can reduce postoperative hypoparathyroidism.

Among the 147 adult participants, 69 were randomly assigned NIRAF, and the remaining 78 underwent surgery without NIRAF. Patients and healthcare personnel involved in nonsurgical care were blinded to NIRAF assignment. The headlight worn by surgeons was turned away to avoid interference with the fluorescent signal.

A primary or first thyroidectomy was conducted in 84 cases, and 63 underwent a completion thyroidectomy. The study’s main goal was the rate of hypoparathyroidism at three months post-surgery, defined as hypocalcemia and abnormally low PTH, and/or continuous treatment with vitamin D.

Rate of hypoparathyroidism 6.5% at three months with NIRAF use

Overall, the rate of hypoparathyroidism after 12 hours was 34%, 17.7% after one month, and 9.2% at three months.

While the rate of hypoparathyroidism was lower with NIRAF than without — at 12 hours (31.8% vs. 35.9%), at one month (14.1% vs. 18.9%), and at three months (6.5% vs. 11.8%) — the differences were not statistically significant at each time point.

Among those who underwent a completion thyroidectomy, PTH and calcium levels before that surgery were within the normal range for all patients except one, who still had hypoparathyroidism after the total thyroidectomy.

The rate by which at-risk parathyroid glands were identified was similar, with and without NIRAF (69.5% vs. 72%). In the NIRAF group, 19 parathyroid glands (9%) only were found due to NIRAF imaging. In four cases, parathyroid glands were detected in tissue by NIRAF after their removal.

All identified parathyroid glands in NIRAF group patients seen in white light could also be observed with the fluorescent signal. Overall, 11 patients (15.9%) in the NIRAF group and three (3.9%) without NIRAF had a parathyroid gland unintentionally removed during surgery.

“In this study with experienced thyroid surgeons performing thyroidectomy, postoperative [hypoparathyroidism] was less frequent in the [NIRAF] group, though not statistically significant, compared with the [no NIRAF] group,” the researchers concluded.

“[NIRAF] imaging appears a valuable tool for [parathyroid gland] identification and may have a special benefit when applied in complicated thyroid surgery,” the researchers noted.