Ectopic parathyroid adenomas located at the carotid bifurcation: the role of preoperative Tc-99m MIBI scintigraphy and the intraoperative gamma probe procedure in surgical treatment planning.

PURPOSE

The prevalence of ectopic parathyroid adenoma (PA) is relatively low, despite some studies in which it has been reported to be as high as 20%. Ectopic PA is a frequent cause of surgical failure, and therefore some authors recommend preoperative imaging to localize the condition in patients with primary hyperparathyroid (HPT) disease before initial surgery.

METHODS

Two unusual cases of primary HPT caused by an ectopic PA located at the carotid bifurcation are reported. The patients were examined before operation using Tc-99m MIBI scintigraphy and then underwent radioguided surgery using the intraoperative gamma probe technique with injection of a low dose (37 MBq; 1 mCi) of Tc-99m MIBI.

RESULTS

The first patient had a history of primary HPT and coexisting multinodular goiter. She had undergone total thyroidectomy in another center, but no enlarged parathyroid gland was found at bilateral neck exploration and serum calcium and parathyroid hormone levels remained elevated after intervention. The patient was referred to our center. A Tc-99m MIBI scan showed a focus of abnormal tracer uptake in the superior left laterocervical region that was thought to be a PA. The next day she underwent radioguided surgery and an 18-mm PA located at the left carotid bifurcation was easily removed through a 2.5-cm skin incision. The second patient was examined in our center before surgery. A neck ultrasound showed a multinodular goiter but no enlarged parathyroid glands. A pertechnectate-MIBI subtraction scan revealed a focus of abnormal Tc-99m MIBI uptake in the right superior laterocervical region that was thought to be a PA. One week later, at radioguided surgery, a 25-mm PA was identified at the right carotid bifurcation and removed successfully.

CONCLUSIONS

These data strongly support the utility of preoperative imaging with Tc-99m MIBI in patients with primary HPT before initial neck exploration with the aim of avoiding surgical failure. Furthermore, the intraoperative gamma probe technique seems to be useful to reduce surgical trauma and, possibly, complications in patients with ectopic PA.