Tracheoesophageal groove: reference point detecting descended superior parathyroid adenoma by SPECT/CT

Objectives: The SPECT appearance of descended superior parathyroid adenoma is described if abnormal focus of activity is inferior posteriorly located in the superior mediastinum. Missing ectopic lesions are critical to the surgeon as the descended superior parathyroid adenoma lies deep to posterior to recurrent laryngeal nerves coursing along the tracheoesophageal groove; otherwise, it becomes frequent sources of persistent hyperparathyroidism. To better localize parathyroid lesions, many investigators have used various techniques such as pin-hole imaging, oblique imaging, SPECT study or SPECT/CT scan. We look for characteristic imaging finding of SPECT/CT for descended superior parathyroid adenoma in superior posterior mediastinum.

Methods: 30 subjects who had parathyroid SPECT/CT were retrospectively reviewed and correlated with a surgical finding to see if imaging finding of superior adenoma by a SPECT and SPECT/CT criteria. All patients had a dual-phase planar parathyroid imaging by utilizing pinhole imaging, RAO and LAO oblique imaging, and SPECT/CT. Images were interpreted with planar images, SPECT without CT and SPECT with CT.

Results: By utilizing SPECT criteria (posteriorly locate to the thyroid, there were six false positives for superior parathyroid adenoma with inferior descent and there were three false negative calling descended superior parathyroid adenoma in the superior mediastinum. By utilizing SPECT/CT criteria (a lesion is anterior or posterior to tracheoesophageal groove), all descended superior parathyroid adenoma to the posterior superior mediastinum were correctly identified.

Conclusions: By identifying a tracheoesophageal groove, SPECT/CT could easily identify the descended superior parathyroid lesion that is in fact, located to posterior to the thyroid and posterior to the tracheoesophageal groove. Understanding the relationship between a superior ectopic parathyroid adenoma and recurrent laryngeal nerve in the tracheoesophageal groove is important.