Identifying an Ectopic Parathyroid Adenoma Using 4DCT in a Pediatric Patient with Persistent Primary Hyperparathyroidism

We present a case of an ectopic mediastinal parathyroid adenoma detected with 4-dimensional computed tomography (4DCT) in a patient with persistent primary hyperparathyroidism and failed neck exploration. We discuss the utility of 4DCT in the localization of these lesions and offer an algorithm that implements the use of 4DCT early on when standard imaging techniques are nonlocalizing. 1. Introduction Minimally invasive and directed extirpation of parathyroid lesions is the goal for patients with primary hyperparathyroidism (PHPT). Current guidelines for preoperative planning include imaging studies, such as a sestamibi scan, ultrasound, or MRI, to localize the adenoma and direct parathyroid surgery. These studies are not useful for patients who have ectopic glands, those located in the mediastinum, retroesophageal space, carotid sheath, thymus, or the thyroid. Roy et al. reported the incidence of occult parathyroid adenomas to be 22%; however, the range of ectopic adenomas has been shown to be from 6 to 16% [1]. For those patients who have failed neck exploration and have nonlocalizing studies, there is a need to accurately detect these lesions in order to decrease morbidity for these patients. 4D computed tomography (CT) has been shown to be useful in detecting these lesions, with a higher sensitivity and specificity than sestamibi scans, ultrasound, and MRI. We present a case report of a pediatric patient with PHPT whose mediastinal parathyroid adenoma was detected on 4-dimensional computed tomography (4DCT) after failed neck explorations and negative ultrasound, sestamibi, and MR imaging. We review the role and technique of 4DCT and provide an algorithm by which to incorporate this new technology in a systematic fashion so that patients with persistent PHPT avoid increased morbidity with a second operation. 2. Case Presentation A twelve-and-a-half-year-old boy was referred for primary hyperparathyroidism to our institution for second opinion for his hypercalcemia. His symptoms included fatigue and muscle pains, and routine laboratory values showed hypercalcemia by his pediatrician, so he was referred for an endocrinology evaluation. His only significant medical history was that he had sustained a right hand fracture the year before. MEN-1 gene testing was performed and was negative. Given his hypercalcemia, the assessment by one endocrinologist was parathyroid adenoma versus four-gland hyperplasia and the patient was referred to ENT for surgical evaluation. One primary ENT surgeon assumed care of the patient upon referral. Imaging workup began with