Transoral Parathyroidectomy Technique

The sublingual approach to transoral parathyroidectomy was the first to be described ^{[12, 13, 14, 15]} ; however, it was associated with a high rate of complications—including hematoma, dysphagia, hypoglossal and recurrent laryngeal nerve injury, and dysgeusia—and has since been largely abandoned in favor of the vestibular approach described by Anuwong. ^[16]  At present, the vestibular approach appears to be the safest and most appropriate surgical option when a transoral approach to parathyroidectomy is being considered.

The procedure is sometimes referred to as TOEPVA (transoral endoscopic parathyroidectomy via the vestibular approach). Robotic approaches have been described. ^{[24, 25]}

As noted previously, the open approach to parathyroidectomy remains the standard of care, and the risks and benefits of alternative surgical approaches should be discussed with the patient in detail.

As described in the literature, ^{[16, 17]}  this endoscopic approach to parathyroidectomy is done entirely via transoral incisions (see the image below).

Approximate oral incision sites for placement of trocars

After induction of general anesthesia and intubation with a nerve-monitoring endotracheal tube, a midline 10-mm incision is made inside the lower lip, approximately 1 cm above the gingivobuccal sulcus, to preserve a cuff of mucosa for closure. Electrocauterization and blunt dissection are employed to expose the mandibular periosteum. Hydrodissection is then accomplished by injecting 1:500,000 epinephrine from inside the incision toward the anterior neck through a Veress needle or a fat injection syringe.

The working space is created by means of blunt dissection with a dilator in a submental and subplatysmal plane. Next, two 5-mm lateral incisions are made on either side of the midline incision, approximately at the junction between the canines and the incisors. Endoscopic ports are then placed, with a 10-mm trocar inserted through the midline incision and two 5-mm trocars inserted in the two lateral incisions. Insufflation is begun at a pressure of 5-7 mm Hg. If a robotic procedure is being done, the robot is docked at this time.

Additional dissection is carried out to create an optimal working space with a subplatysmal pocket that should extend inferiorly to the level of the sternum and laterally to each sternocleidomastoid muscle. The midline raphe of the strap muscles is divided, and the strap muscles are dissected laterally to expose the thyroid gland. These muscles can be retracted laterally by using 2.0 silk as an external hanging suture.

The dissection continues in a capsular plane around the thyroid gland. The upper parathyroid glands are typically found in this capsular plane at the posterior aspect of the superior pole. If the parathyroid glands are prominent, they can be seen with retraction of the thyroid medially. If they are normal in size, dissection of the superior thyroid vessels with an ultrasonic scalpel may be required for better mobilization of the superior pole of the thyroid.

Removal of the lower parathyroid glands may necessitate identification and dissection of the recurrent laryngeal nerve; these glands are often located at the junction between this nerve and the inferior thyroid artery. The abnormal gland(s) can be removed with an ultrasonic scalpel and retrieved with an endoscopic bag through the midline vestibular incision.

Intraoperative frozen specimens can be sent to confirm removal of abnormal parathyroid tissue. Additionally, an intraoperative parathyroid hormone (PTH) level may be obtained 10-15 minutes after removal of the abnormal gland(s) to assist in confirming whether further exploration is needed (see Parathyroidectomy).

Hemostasis is confirmed and the surgical site irrigated. The strap muscles are reapproximated with 3-0 absorbable suture, and the oral vestibule incisions are closed with layered absorbable sutures. A compression dressing is then applied over the neck and chin, and the patient is transferred to the anesthesia team for extubation.

Postoperative management is largely based on individual surgeons' preferences. Typically, however, patients are monitored at least overnight with regular (eg, every 6 hours) serum calcium checks and are discharged home the next day if calcium levels remain stable. Serum calcium should continue to be followed on an outpatient basis, as should postoperative vocal cord function via flexible fiberoptic laryngoscopy or indirect mirror examination.

The pressure dressing placed in the operating room can be removed on postoperative day 1, before the patient is discharged home. Follow-up appointments should check for any fluid that may have collected in the submentum or anterior neck because of the large subplatysmal space created during the parathyroidectomy.

As with open thyroid and parathyroid surgical procedures, one of the most serious complications is injury to the recurrent and superior laryngeal nerves. Identification and careful dissection of these structures during the operation are therefore critical, particularly if there is any difficulty in identifying the abnormal gland(s). Additional complications include hematoma or seroma, postoperative hypocalcemia, failure to correct hyperparathyroidism and hypercalcemia, and the need for further procedures in the future.

As with any surgical procedure, bleeding and infection are potential complications. Because transoral parathyroidectomy is a clean-contaminated procedure, there is an increased risk of infection, though a number of case reports failed to document perioperative infection or abscess with this technique. ^{[14, 15, 16, 17, 21]}

Several other complications are specific to this surgical approach. The mental nerves are at risk for injury if the oral vestibule incisions are improperly placed. The creation of the subplatysmal pocket and the use of CO₂ insufflation give rise to a potential for subcutaneous emphysema, pneumomediastinum, or both. This subplatysmal pocket may also increase the rate of postoperative hematoma or seroma, though, on the basis of the current literature, this appears to be a rare complication. ^{[16, 17, 21]}

A review of 32 Turkish patients who underwent successful TOEPVA at 11 centers cited a 19% rate of complications. ^[26] These included ecchymosis, subcutaneous emphysema, nasal bleeding, surgical-site infection, and seroma; however, there were no recurrent nerve palsies, nor were there any mental nerve root or branch injuries.