IMAGING LOCALIZATION AND SURGICAL APPROACH IN THE MANAGEMENT OF ECTOPIC PARATHYROID ADENOMAS

( 1) Review the anatomy and epidemiology of ectopic parathyroid adenomas (EPAs), ( 2) summarize the role of relevant imaging modalities in the localization of EPAs, and ( 3) characterize surgical approaches for various ectopic locations. Literature review of published English-language articles from 1995 through August 2017. Summary of the literature indicates that the prevalence of EPA is approximately 20% in unexplored patients with primary hyperparathyroidism, but it is as high as 66% in re-operative patients. EPAs may be located anywhere from the carotid bifurcation to the aorto-pulmonary window. Ultrasound has limited accuracy in identifying EPAs except near the thyroid and thyrothymic ligament and requires expert experience from the user. Among dual-phase Tc sestamibi scintigraphy techniques, hybrid imaging with both single-photon emission computed tomography (SPECT) and computed tomography (CT) (SPECT/CT) is superior to planar scintigraphy or SPECT alone at localizing EPAs. Four-dimensional computed tomography (4DCT) precisely delineates important anatomic relationships and is highly sensitive in localizing EPAs. Although 4DCT requires radiation, intravenous iodinated contrast, and reader experience, it is well-equipped to detect lesions at various ectopic sites and guide the surgical approach. EPAs frequently require alternative surgical approaches. Re-operative parathyroidectomy may be attempted in patients having previously undergone bilateral neck exploration by an experienced surgeon once the lesion is colocalized by 2 repeat imaging modalities. Removal of nonlocalized disease requires a careful and systematic exploration of superior and inferior gland locations. EPAs pose challenges during both localization and surgical removal. High-volume experience and multidisciplinary care are necessary for optimal outcomes. CT = computed tomography; 4DCT = 4-dimensional CT; EPA = ectopic parathyroid adenoma; EPG = ectopic parathyroid gland; PHPT = primary hyperparathyroidism; RLN = recurrent laryngeal nerve; SPECT = single-photon emission computed tomography; TE = tracheo-esophageal.