E1269. Ectopic Parathyroid Adenomas: A Case-Based Imaging Review
  1. Dagan Kaht; Cleveland Clinic
  2. Steve Huang; Cleveland Clinic
  3. Donald Neumann; Cleveland Clinic
The purpose of this exhibit is to educate the viewer about ectopic hyperactive parathyroid adenomas. Primary hyperparathyroidism is most commonly caused by a solitary hyperactive adenoma, the majority of which are located posterior to the thyroid in their expected orthotopic position, but approximately 5-22% are ectopic. These ectopic parathyroid adenomas can pose a challenge for localization and surgical removal, leading to prolonged adverse patient effects. Understanding where to look for parathyroid adenomas outside of their typical orthotopic distribution is critical.

Educational Goals / Teaching Points
After participating in this educational exhibit the viewer will become familiar with parathyroid gland function and embryology, the multi-modality imaging techniques used to localize abnormal parathyroid adenomas, the imaging features, and the variety of ectopic locations via case-based review.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This exhibit will review the function of the parathyroid glands, notably the maintenance of calcium homeostasis, as well as their embryology from the third and fourth pharyngeal pouches. Scintigraphic imaging with technetium 99m sestamibi can be combined with radioiodine scintigraphy and computed tomography (CT) for increased sensitivity and localization of ectopic adenomas. Parathyroid adenomas appear as focal sites of increased sestamibi uptake and as avidly enhancing lesions on intravenous contrast CT. Ectopic adenomas can be found in a myriad of locations including the carotid sheath, submandibular, intrathymic, mediastinum, tracheoesophageal groove, and retropharynx.

Accurate localization of ectopic parathyroid adenomas can have a significant impact on the treatment of primary hyperparathyroidism and the radiologist, with appropriate knowledge, plays a vital role.