Operative Approach

A Kocher collar incision is made. The incision is deepened down through the platysma, and superior and inferior sub-platysmal flaps are developed. The median raphe is divided and the strap muscles are retracted laterally without division. The thyroid lobes are sequentially elevated, and all four parathyroid glands and any supernumerary glands are exposed. Most supernumerary glands are located in proximity to the other glands or less often in ectopic locations. Transcervical thymectomy should be performed to rule out a supernumerary gland and to evaluate the thymus for a carcinoid tumor. Failure to identify a superior gland necessitates mobilization of the superior thyroid pole by individually lig-ating the superior thyroid artery and vein or their branches on the thyroid capsule. This helps avoid injury to the external branch of the superior laryngeal nerve. Rotation of the upper pole upward and outward often brings the superior gland into view. Larger superior glands can migrate along the tracheoesophageal groove, into the retroesophageal space, and down into the posterior mediastinum. These can usually be elevated into the wound with adequate exposure and gentle traction. Missing inferior glands should be sought within the thymus, the carotid sheath, in an undescended location in front of the carotid bifurcation, and just beneath the thyroid capsule, typically along its inferior pole. The rare undescended superior parathyroid gland can be located within the pharyngeal musculature. Intraoperative ultrasonography (IOUS) may be of aid in locating ectopic glands within the neck.81

Once four glands have been identified and the transcervical thymectomy has been performed, the surgeon then proceeds with a subtotal parathyroidectomy.82 It is our preference to leave behind an inferior gland or a portion thereof, depending on its size. Leaving an inferior gland or remnant makes reoperation safer because of the inferior gland's distance from the recurrent laryngeal nerve. If a superior gland is much smaller or grossly normal compared to the rest, we would consider leaving this as the remnant. The vascularized remnant should be approximately 50 to 60 mg in weight.83"85 The remnant should be prepared prior to excising the other glands so as to ensure its viability prior to completing the subtotal parathyroidectomy. If the remnant becomes devas-cularized, it should be removed and the other inferior gland trimmed. The remnant or remaining gland should be tagged with a nonabsorbable suture or preferably a metal clip. Additional parathyroid tissue should be cryopreserved or immediately autotransplanted (multiple small pieces totaling 50 to 60 mg) into a small, infraclavicular, subcutaneous pocket. Despite earlier reports regarding the efficacy of cry-opreservation86"88 and the viability of cryopreserved tissue in vitro studies,89 we have used few of the hundreds of cryopreserved specimens stored at Mayo Clinic. When used, rarely have these delayed autotransplants resulted in meaningful restoration of normal parathyroid function. It is now this surgeon's (GBT) practice, when performing a subtotal parathyroidectomy, to transplant 50 to 60 mg of nonmalig-nant parathyroid tissue into a chest wall subcutaneous pocket just below the clavicle. If the immunometric PTH level is >1 pmol/L (normal, 1 to 5 pmol/L) 24 hours postoperatively, the transplant is removed at the bedside. If the postoperative immunometric PTH is below the level of detection, the transplant is left in place. Time will tell whether graft-dependent recurrences will be easier to detect and manage in this location, but it is thought to be the case. By placing the graft close to the deltopectoral groove, below the clavicle, selective venous sampling (SVS) (subclavian vein) can be used along with SPS and ultrasound to evaluate for graft-dependent recurrence.

Another option for managing MEN 1 primary HPT is total parathyroidectomy, transcervical thymectomy, and immediate forearm autotransplantation.86,87,90 Autotransplantation is classically carried out by implanting 10 to 15 (1-mm) pieces of fresh tissue into multiple pockets of the nondominant, brachioradialis forearm muscle. Each site is marked with a fine, monofilament nonabsorbable suture for future reference. The forearm skin incision should be made in a longitudinal fashion so as to avoid confusion with regard to a self-inflicted wound. Recurrence rates are extremely low following total parathyroidectomy, but permanent hypoparathyroidism rates can be unacceptably high.91"93 Later explantation is also more formidable with regard to intramuscular implants.

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