Parathymic parathyroid: CT, US, and angiographic findings.

Six patients with primary hyperparathyroidism caused by an undescended parathymic adenoma are described. All glands were anterior to the common carotid artery at the level of the hyoid bone. Blood supply was from the superior thyroid artery, and venous drainage was into the superior thyroid vein. Ultrasound (one of five) and computed tomography (two of six) were rarely positive, but glands can be detected with both modalities if the examination is carried high enough. Glands within the carotid sheath are generally lower in the neck and have a blood supply from the inferior thyroid artery with drainage into the vertebral veins.