Photodynamic identification of human parathyroid glands with 5-aminolevulinic acid

Tumors synthesize fluorescent and photosensitizing endogenous protoporphyrin after administrations of 5-aminolevulinic acid (5-ALA). Localization of tumors and tumor-like lesions in various organs that are labeled with fluorescing porphyrins has thus developed into a diagnostic method. Intraoperative photodynamic detection of malignant gliomas is the most common application, and has been widely performed since 1998. Although several methods to identify parathyroid glands have been employed, photodynamic methods have not yet been used for this application. In 2004, Shimizu et al. showed that human parathyroid glands could be identified photodynamically with 5-ALA. We have performed photodynamic identification of human parathyroid glands in an additional 19 cases. In hyperparathyroidism, detection of morbid parathyroid glands is extremely important. On the other hand, the identification and preservation of normal parathyroid glands is important for preventing hypoparathyroidism after thyroid surgery. Our method allows the visualization of both morbid and normal parathyroid glands. We believe that intraoperative photodynamic identification of human parathyroid glands is feasible and practical, allowing less-invasive, more-precise neck surgery.