The Undescended "Parathymus" An Occasional Cause of Failed Neck Exploration for Hyperparathyroidism ANTHONY J. EDIS, M.D., DON C. PURNELL, M.D., JONATHAN
Arrested descent of the inferior parathyroid gland ("parathymus") during embryologic development may leave the gland stranded high in the neck. Adenomas of such undescended glands are a rare cause of primary hyperparathyroidism, but they may not be uncommon among patients who have already had a failed cervical exploration. Unless the surgeon is aware of this entity, he will probably overlook it. If one is to find these tumors, it is necessary to extend the dissection upward above the superior pole of the thyroid gland, sometimes as far as the angle of the jaw. Adenomas of undescended "parathymus" glands were encountered in seven patients during a recent 20 month (May 1975 through December 1976) surgical experience encompassing 414 primary operations and 27 reoperations for hyperparathyroidism. These tumors were found at initial exploration in one patient and at reoperation in six patients. The individual case histories are presented to illustrate the difficulties posed by this anatomic variant.
S UCH IS THE PROXIMITY of the inferior parathyroid gland to the thymus during embryologic development that Weller9 called it the "parathymus" gland (Fig. 1). This is a useful descriptive term because it serves to remind the surgeon that, in almost half the
patients undergoing cervical exploration for hyperparathyroidism, an inferior parathyroid will be found within the thymic tongue at the thoracic inlet.7 Similarly, one can readily appreciate how the inferior parathyroid might occasionally overshoot its usual adult location during caudal descent and end up with the thymus in the mediastinum. About 1-2% ofpatients with primary hyperparathyroidism will be found to have an adenoma arising in one of these ectopic mediastinal "parathymus" glands.4'6 Arrested descent ofthe third branchial pouch complex may also occur and leave the inferior parathyroid Reprint requests: Anthony J. Edis, M.D., Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901. Submitted for publication: January 22, 1979.
A. VAN HEERDEN, M.B.,
From the
Mayo Clinic and Mayo Foundation, Rochester, Minnesota
stranded high in the neck. Sometimes, a small amount of thymus is still attached to this undescended gland, and this serves to identify the latter as "parathymus." This phenomenon occurs infrequently: in a recent anatomic study of normal parathyroid glands in postmortem subjects, Wang7 found only three of 312 inferior parathyroid glands in an undescended location. This report describes seven patients with primary hyperparathyroidism due to adenomas of undescended "parathymus" glands. Six of these tumors were overlooked at initial cervical exploration and were ultimately found at reoperation by extending the dissection into the zone above the superior pole of the thyroid. Our belated recognition of this unusual anatomic variant finally permitted expeditious identification and removal of an undescended "parathymus" adenoma in a seventh
patient at primary operation. Our purpose in reporting these cases is to acquaint those interested in parathyroid surgery with this problem. To our knowledge, only one other case has been previously described,8 and it is doubtful that many surgeons recognize the existence of the phenomenon. Case
Reports
Case 1. In August 1973, this 20-year-old man underwent cervical exploration (elsewhere) for primary hyperparathyroidism complicated by nephrolithiasis. An adenoma of the left superior parathyroid gland weighing 2.2 g was removed, and a normal right inferior parathyroid gland was also excised. Neither of the two remaining glands was identified. The patient remained hypercalcemic postoperatively. His subsequent clinical course was complicated by the necessity for left ureterolithotomy in November 1974. He was first seen at the Mayo Clinic in May 1975, at which time the serum level of calcium was 12.1 mg/dl (normal range 8.9- 10.1 mg/dl) and the serum concentration of immunoreactive parathyroid
0003-4932/79/0700/0064 $00.75 C J. B. Lippincott Company
64
F.R.C.S(C)
Vol. 190
. No.
1
UNDESCENDED PARATHYMUS
65
Pharynx
hormone (iPTH)* was 75 ,uleq/ml (normal
Arrested descent of the inferior parathyroid gland ("parathymus") during embryologic development may leave the gland stranded high in the neck. Adenomas of such undescended glands are a rare cause of primary hyperparathyroidism, but they may not be uncommon among patients who have already had a failed cervical exploration. Unless the surgeon is aware of this entity, he will probably overlook it. If one is to find these tumors, it is necessary to extend the dissection upward above the superior pole of the thyroid gland, sometimes as far as the angle of the jaw. Adenomas of undescended "parathymus" glands were encountered in seven patients during a recent 20 month (May 1975 through December 1976) surgical experience encompassing 414 primary operations and 27 reoperations for hyperparathyroidism. These tumors were found at initial exploration in one patient and at reoperation in six patients. The individual case histories are presented to illustrate the difficulties posed by this anatomic variant.
S UCH IS THE PROXIMITY of the inferior parathyroid gland to the thymus during embryologic development that Weller9 called it the "parathymus" gland (Fig. 1). This is a useful descriptive term because it serves to remind the surgeon that, in almost half the
patients undergoing cervical exploration for hyperparathyroidism, an inferior parathyroid will be found within the thymic tongue at the thoracic inlet.7 Similarly, one can readily appreciate how the inferior parathyroid might occasionally overshoot its usual adult location during caudal descent and end up with the thymus in the mediastinum. About 1-2% ofpatients with primary hyperparathyroidism will be found to have an adenoma arising in one of these ectopic mediastinal "parathymus" glands.4'6 Arrested descent ofthe third branchial pouch complex may also occur and leave the inferior parathyroid Reprint requests: Anthony J. Edis, M.D., Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901. Submitted for publication: January 22, 1979.
A. VAN HEERDEN, M.B.,
From the
Mayo Clinic and Mayo Foundation, Rochester, Minnesota
stranded high in the neck. Sometimes, a small amount of thymus is still attached to this undescended gland, and this serves to identify the latter as "parathymus." This phenomenon occurs infrequently: in a recent anatomic study of normal parathyroid glands in postmortem subjects, Wang7 found only three of 312 inferior parathyroid glands in an undescended location. This report describes seven patients with primary hyperparathyroidism due to adenomas of undescended "parathymus" glands. Six of these tumors were overlooked at initial cervical exploration and were ultimately found at reoperation by extending the dissection into the zone above the superior pole of the thyroid. Our belated recognition of this unusual anatomic variant finally permitted expeditious identification and removal of an undescended "parathymus" adenoma in a seventh
patient at primary operation. Our purpose in reporting these cases is to acquaint those interested in parathyroid surgery with this problem. To our knowledge, only one other case has been previously described,8 and it is doubtful that many surgeons recognize the existence of the phenomenon. Case
Reports
Case 1. In August 1973, this 20-year-old man underwent cervical exploration (elsewhere) for primary hyperparathyroidism complicated by nephrolithiasis. An adenoma of the left superior parathyroid gland weighing 2.2 g was removed, and a normal right inferior parathyroid gland was also excised. Neither of the two remaining glands was identified. The patient remained hypercalcemic postoperatively. His subsequent clinical course was complicated by the necessity for left ureterolithotomy in November 1974. He was first seen at the Mayo Clinic in May 1975, at which time the serum level of calcium was 12.1 mg/dl (normal range 8.9- 10.1 mg/dl) and the serum concentration of immunoreactive parathyroid
0003-4932/79/0700/0064 $00.75 C J. B. Lippincott Company
64
F.R.C.S(C)
Vol. 190
. No.
1
UNDESCENDED PARATHYMUS
65
Pharynx
hormone (iPTH)* was 75 ,uleq/ml (normal
