Undescended superior parathyroid gland: a potential cause of failed cervical exploration for hyperparathyroidism

The undescended inferior parathyroid gland is a well-established although infrequent embryologic abnormality resulting in an ectopically located gland usually associated with thymic tissue and is found most commonly within the carotid sheath at the level of the carotid bifurcation. Embryologically undescended superior glands (either normal or enlarged), clearly above the level of the upper pole of the thyroid gland and found within or in approximation to the lateral pharyngeal wall, have not been previously described.

The locations of all parathyroid glands at the time of cervical exploration were carefully examined as to embryologic origin in a combined experience of more than 3000 patients with primary or secondary hyperparathyroidism.

Five patients had enlarged abnormal glands located within or in close approximation to the pharyngeal wall. All were above the upper pole of the thyroid gland. Two were identified at reoperation on the basis of localization studies. One gland was found after resection of a massive concomitant cervical goiter. The other two were found after an extensive search for a superior gland.

Undescended superior glands are extremely rare (0.08%). They are located within or in approximation to the pharynx above the level of the thyroid gland with an unusual blood supply, which supports an embryologic rather than acquired cause for their ectopic location.