Methods of identification of parathyroid glands in thyroid surgery: A literature review

Intra-operative identification and preservation of parathyroid glands is an important but challenging aspect of thyroid surgery. Failure to do so may lead to transient or permanent hypocalcaemia, where the latter represents a serious complication causing life-long morbidity. It would be beneficial, therefore, if a simple and reliable modality can be developed to assist in the identification of parathyroid glands intra-operatively. The aim of this literature review is to provide an overview of intra-operative modalities used to identify parathyroid glands with a particular focus on near-infrared autofluorescence (NIRAF). Twenty-seven studies were considered relevant in this literature review. Several modalities have been used to aid parathyroid gland identification, including Raman spectroscopy, indocyanine green angiography, and NIRAF. NIRAF technology allows parathyroid glands to spontaneously give off light (autofluorescence) when exposed to near-infrared light at a wavelength of 785 nm, creating a contrast between tissues to allow intra-operative differentiation. Studies utilising NIRAF technology were able to identify 76.3%-100% of parathyroid glands intra-operatively. Furthermore, two randomised controlled trials comparing NIRAF and white light showed that the use of NIRAF was able to significantly increase the mean number of parathyroid glands detected and reduce the incidence of post-operative hypocalcaemia. NIRAF is an emerging tool that has been shown to increase the number of intra-operative parathyroid gland identification and reduce the rate of post-operative hypocalcaemia in a safe and reproducible manner. Future trials are needed to evaluate the real-life impact of NIRAF technology in outcomes of patients following thyroid surgery.