Minimally Invasive Resection of Mediastinal Parathyroid Adenoma using SPECT/CT and Intact PTH Monitoring

Introduction

The incidence of primary hyperparathyroidism has been estimated to be 2–5/100000 with ectopic parathyroid glands being found in 10% of pediatric cases [1]. Due to size limitations in children and the difficulty in gaining adequate access to the mediastinum, ectopic mediastinal lesions have historically been accessed via either a thoracotomy or a sternotomy. However, with advanced imaging techniques providing more precise localization, it is now possible to consider a minimally invasive mediastinal approach in children. We report here on a novel approach for children with mediastinal parathyroid disease that includes use of a new fusion imaging modality combining both nuclear and computed-tomography (CT) imaging techniques to provide a functional and anatomical assessment, the monitoring of intraoperative intact parathyroid hormone (iPTH) levels and use of a minimally invasive trans-cervical approach using a fixed arm retractor.

A 10-year-old patient presented with a 2-week history of abdominal pain and acute pancreatitis. Laboratory analysis revealed an elevated amylase and lipase (1681 and 923 U/L), parathyroid hormone (PTH) (258 pg/ml) and hypercalcemia (total calcium 17.2 mg/dl, ionized calcium 2.4 mmol/L). The pancreatitis resolved with conservative management while the hypercalcemia required saline diuresis, calcitonin and pamidronate. Parathyroid imaging localization studies included neck ultrasound, conventional computed tomography (CT) scan, and single photon emission computed tomography/computed tomography (SPECT/CT) study using Tc-99 m sestamibi (MIBI). SPECT/CT, a newer fusion imaging modality combining both nuclear SPECT and X-ray CT imaging techniques in one scanner, allows both functional and anatomical assessment of disease. An ectopic parathyroid adenoma was localized by SPECT/CT to the anterior superior mediastinum adjacent to the lateral aspect of the right thymus and anterior to the right pulmonary artery ([Fig. 1a–c]). A 1.75 cm, suprasternal incision and a table-mounted fixed retractor for the sternum were utilized for mediastinoscopy and resection of the mediastinal parathyroid adenoma and right thymus ([Fig. 2]). Intraoperative intact parathyroid hormone (iPTH) levels were obtained via the right internal jugular vein prior to making the incision (793 pg/ml), immediately prior to adenoma removal (477 pg/ml) and 10 min after adenoma removal (36 pg/ml), eliminating the need for further mediastinal or neck exploration. Histological analysis confirmed the diagnosis of parathyroid adenoma. Once postoperative calcium levels had stabilized, the patient was discharged on postoperative day 4.

Fig. 1 (a–e) a Axial SPECT, b Axial SPECT/CT fusion. c Coronal SPECT. d Coronal SPECT/CT fusion. e Sagittal SPECT/CT fusion. The images reveal abnormal tracer uptake localized to the right anterior superior mediastinum along the lateral aspect of the thymus, consistent with ectopic parathyroid adenoma.

Fig. 2 Fixed table retractor used to retract the sternum anteriorly through a small cervical incision.

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