Rapid Intraoperative Localization of Parathyroid Glands Utilizing Methylene Blue Infusion

Abstract

OBJECTIVE: To review a single surgeon's experience utilizing an intraoperative methylene blue infusion (IMBI) to identify parathyroid glands during neck exploration for primary hyperparathyroidism. STUDY DESIGN AND SETTING: Retrospective review of 35 patients who underwent bilateral neck exploration utilizing an IMBI at a dose of 7.5 mg/kg following the induction of general anesthesia. RESULTS: All patients reverted to normocalcemia with a mean follow-up of 17 months. IMBI facilitated the identification of abnormal parathyroid tissue in 34/35 patients (97%). A dark blue-purple staining was observed in 33/37 stained adenomas (89%). Four adenomas and four hyperplastic glands stained a lighter shade of blue-green. Among 89 normal glands, 41(46%) stained a pale green-grey color. CONCLUSIONS: IMBI is a safe, readily available, cost-effective, and underutilized technique that facilitates rapid identification of parathyroid adenomas, helps distinguish normal glands from hyperplastic glands, and helps to locate ectopic glands. An overall reduction in operative time, especially for bilateral neck exploration, can be anticipated. Since parathyroid glands are often inconspicuous, their identification can be a challenging problem when performing neck exploration for the treatment of hyperparathyroidism. Normal parathyroid glands can be a few millimeters in size (especially when suppressed by hypercalcemia), of variable color, and supernumerary. They may also be surrounded by or imbedded in adipose tissue or confused with small paratracheal lymph nodes. When thyroid surgery is performed by experienced surgeons, inadvertent parathyroidectomy may be as high as 9%. 1 Abnormal parathyroid glands may be concealed beneath the thyroid capsule, intrathyroid, intrathymic, or inside the carotid sheath. Other ectopic locations in the neck or anterior mediastinum are also encountered. Furthermore, the distinction between true double adenomas and asymmetric hyperplasia continues to challenge even the most seasoned endocrine surgeon. It has been argued that with the exception of a mediastinal parathyroid adenoma, localizing studies (eg, technetium-99m-sestamibi [Tc-MIBI] imaging, MRI, CT, and ultrasound [US]) add little to the overall success of parathyroidectomy, especially for primary explorations in the hands of experienced endocrine surgeons. However, for the less experienced surgeon, preoperative localization studies have been helpful in directing the side of the neck for initial exploration, and for reducing operative times and frustration. Revision parathyroidectomy, after a failed initial neck exploration, can be an exercise in futility without some form of localizing study, the cost of which is then always justified. Recent extramural pressures to perform “minimally invasive surgery,” limiting both the scope and duration of parathyroidectomy and reducing hospital length of stay, have popularized the use of preoperative parathyroid localizing studies. Over the past decade, Tc-MIBI imaging has become the “gold standard” for preoperative localization because of its high sensitivity and specificity, and its use has become routine in many centers. Intraoperative procedures such as Tc-MIBI localization using a hand-held gamma probe, intraoperative circulating iPTH assay (Nichols Institute Diagnostics, San Juan Capistrano, CA, USA), have evolved to permit a more limited “minimally invasive” unilateral neck exploration. However, this approach is limited to patients for whom a preoperative Tc-MIBI strongly suggests the presence of a single adenoma. Even with this positive finding, Tc-MIBI will miss double adenomas and asymmetric four-gland hyperplasia in a significant number of patients. The additional radiation exposure to patient and personnel with radioguided surgery, the need for more than one scan, and complex scheduling issues for appropriate timing of the radiopharmaceutical administration may represent other disadvantages.