Determinant role of Tc-99m MIBI SPECT in the localization of a retrotracheal parathyroid adenoma successfully treated by radioguided surgery.

Purpose: The authors' aim was to evaluate the role of MIBI SPECT acquired just after planar pertechnetate-MIBI (TcO(4)-MIBI) subtraction scintigraphy in planning radioguided surgery in a patient with persistent primary hyperparathyroidism after initial surgery performed to treat a retrotracheal parathyroid adenoma (PA).

Methods: A 73-year-old man with persistent primary hyperparathyroidism after a previous left parathyroidectomy and left thyroid lobectomy is described. The patient was examined in our center in a single-day preoperative imaging protocol based on findings of planar TcO(4)-MIBI subtraction scintigraphy, MIBI SPECT, high-resolution neck ultrasound, and computed tomography.

Results: Neck ultrasound did not reveal enlarged parathyroid glands. Findings of a neck-chest computed tomographic scan were also inconclusive. Instead, planar scintigraphy clearly depicted a single focus of MIBI uptake over the thyroid gland in a median position. The SPECT examination precisely localized a PA in the retrotracheal space. The day after imaging, the patient underwent unilateral left cervical surgical exploration. A 16 x 21 mm PA was easily detected using the gamma probe technique after injection of a low dose of 37 MBq (1 mCi) Tc-99m MIBI, and the PA was rapidly removed with limited surgical trauma. Rapid serum PTH and calcium levels normalized after intervention and remained in the normal range during subsequent follow-up.

Conclusions: The current data indicate the importance of preoperative imaging with MIBI scintigraphy in patients with primary hyperparathyroidism and strongly support the utility of MIBI SPECT acquisition in PAs located deep in the neck and in ectopic sites. Furthermore, the gamma probe can help the surgeon to detect the PA during surgery and to minimize the surgical trauma in patients who have had previous thyroid or parathyroid surgery.