Transoral thyroid and parathyroid surgery via the vestibular approach—a 2020 update

Introduction

For more than 100 years, thyroid surgery has been safely performed via an anterior neck incision (1). This scar heals well in the majority of patients, with generally acceptable cosmetic outcomes. Despite this, nearly 20% of patients will experience some feelings of self-consciousness years after thyroid surgery, while more than 10% will consider further treatments such as plastic surgery to improve the appearance of their scars (2). The impact of a cervical incision on the health related quality of life (HRQOL) was found to be similar to the impact of vitiligo, psoriasis, or severe atopic dermatitis in one series (3). Because excellent cosmesis cannot be guaranteed, remote-access thyroid surgery has evolved to address the potential morbidity of an anterior cervical incision (4). Unfortunately, the perception of a scar can vary between patients and surgeons, further impairing the ability of patients to achieve optimal cosmesis (5-7).

Before (TOET/PVA), remote-access thyroid and parathyroid surgery techniques have succeeded in avoiding an anterior neck incision by relocating the cutaneous incision to less conspicuous locations. Common examples include areolar or axillary incisions, which can effectively minimize the cosmetic burden in some patients. Despite the improved local cosmesis, these techniques may be challenging due to unfamiliar dissection planes, longer routes to the central neck, and novel complications. Additionally, a steep learning curve has been demonstrated, with long initial operative times (4). Consequently, the adoption of these alternative techniques was slow, especially in the West (4).

In 2016, Anuwong published the first case series of 60 patients who underwent scarless thyroidectomy via the lower vestibule of the mouth with excellent outcomes (8). This came as a result of worldwide efforts to explore an alternative remote-access thyroidectomy approach, specifically by utilizing natural orifice transluminal endoscopic surgery (NOTES) concepts (9-14). The first attempts were discouraging, as the sublingual approach resulted in devastating adverse effects, including hypoglossal nerve injury (15,16). Subsequently, Richmon et al. utilized the oral vestibule as an alternative to the sublingual approach (12) which was ultimately adopted by Anuwong.

Following the initial series, multiple institutions around the world have adopted this new technique with similar results (17-32). Currently, TOETVA, with approximately 900 reported cases, perhaps more than other remote-access techniques, is attracting patients who are interested in avoiding a neck scar (17,33). In the West, the endoscopic approach far exceeds the robotic approach, as the latter requires extended operative time, a longer learning curve and, occasionally, an axillary incision for the fourth arm of the robot (24). This manuscript aims to update the reader on the status of transoral thyroid and parathyroid surgery via the vestibular approach.

Indication and contraindications

TOETVA

TOETVA surgical indications and contraindications have evolved since its first description in patients by Anuwong in 2016 (8) and are largely practice or institution specific (34). Fifty-five percent of patients undergoing thyroid and parathyroid surgery—approximately 150,000 patients in the US—are estimated to be eligible for transoral endocrine surgery using the most widely accepted guidelines (35). In this section, we will describe the current TOETVA inclusion and exclusion criteria in the literature. Current TOETVA inclusion and exclusion criteria of our practice are described in Table 1.

Table 1 Johns Hopkins’ TOETVA inclusion and exclusion criteria
Full table

TOETVA is intended for carefully selected patients. Primarily, candidates must be motivated to avoid an anterior cervical scar and/or have a history of hypertrophic scarring or keloids. Indications for TOETVA include both benign and malignant conditions. Symptomatic grade I goiter (anterior mediastinum) and Grave’s disease can be approached through TOETVA (36). Specific inclusion criteria for thyroid preoperative ultrasonography size and volume and index nodule size vary between different institutions and authors. Thyroid gland size cutoffs include a diameter of 8–10 cm (8,37,38) or estimated thyroid volume ≤45 mL, with a nodule size cutoff between 4–6 cm among benign or cytologically indeterminate (Bethesda II, III, IV) nodules (30,31,39). For patients with nodules that are suspicious for malignancy (Bethesda V) or confirmed well-differentiated thyroid cancer without evidence of metastasis, a maximum index nodule size of 2 cm has been utilized, which has been shown to be a safe threshold (36,40). If completion thyroidectomy is necessary, a repeat-TOETVA for the contralateral thyroid gland can be safely performed within 3 weeks. After that window, it may be appropriate to consider completion TOETVA after 6 months (41,42).

Current TOETVA exclusion criteria include lateral neck or extrathyroidal disease extension, pre-operative RLN paresis, prior trans-cervical neck surgery, oral abscesses, or patient intolerance to general anesthesia. Previous transoral neck surgery and neck radiation are not absolute contraindications (37,43). Patient age or body mass index (BMI) are not absolute contraindications to surgery.

Surgeon candidacy

In addition to careful patient selection, surgeon candidacy is of utmost importance for procedure safety. Prior to learning (TOET/PVA), a surgeon must be proficient in the standard procedures of the central neck, including thyroidectomy, parathyroidectomy, and central neck dissection in case of necessary conversion to an open (standard) approach (44). High volume (bare minimum is more than 25 thyroid surgeries per year) surgeons have significantly improved outcomes and decreased costs in comparison to low volume surgeons (45,46) with conventional cervical thyroidectomy, and an adequate volume is required to overcome the learning curve with any new technique. A study by Razavi et al. describing the TOETVA learning curve using operative time as a surrogate concluded that 11 cases were needed for procedural proficiency, which is similar to the 15 case curve described for video-assisted thyroidectomy (47,48). However, this study represented the learning curve of only one surgeon in a high volume tertiary hospital and may not be germane to other settings. Further data to determine a requisite number of open thyroidectomies in order to perform transoral thyroid surgery is not available (44). The surgeon must also demonstrate competence with relevant instrumentation and advanced laparoscopy in order to avoid novel and/or serious complications (44). This requires case observations, cadaveric dissections, and mentored initiation of cases to ensure the safety of this novel procedure (41). In addition to surgeon familiarity, all operating room staff should be familiar with the procedure and their respective roles.

Transoral endoscopic parathyroidectomy vestibular approach (TOEPVA)

TOEPVA can also be performed for select patients with localized primary hyperparathyroidism (HPT). Those without parathyroid adenoma localization, recurrent or persistent primary HPT, suspected multigland disease, secondary or tertiary HPT, family history of MEN, suspected parathyroid carcinoma, or previous central neck surgery or neck irradiation therapy should be excluded from consideration. Similar to TOETVA, the patient should also be highly motivated for a “scarless” approach. The authors recommend two imaging modalities with concordant findings, usually surgeon performed ultrasound and sestamibi with multi-phase CT, for localization prior to offering TOEPVA. This has shown to have a positive predictive value of up to 99% for localization (49).

Surgical steps and perioperative consideration

Perioperative considerations

After confirming eligibility for transoral thyroid surgery, the patient should be aware of all the potential outcomes of the procedure, including numbness of the lower lip and chin. We also stress that the subcutaneous scar tissue will induce mild symptoms of dysesthesia for some time in the midline chin. Additionally, we stress the possibility of conversion to an open technique if deemed appropriate to ensure safety of the patient and completeness of the procedure, as well as the limitations with regards to oncologic outcomes given the lack of long term oncologic follow up. Surgeon-directed ultrasound has a vital role in determining eligibility as well as in surgical planning in clinic and prior to port placement in our practice. Patients should be educated about postoperative care including use of antibiotics, wound care and a suggested set of postoperative exercises to hasten recovery (50).

Intraoperative highlights

TOETVA surgical developments have been seen in trocar placement and intraoperative neuromonitoring (IONM) use. Three incisions are made in the lower vestibule of the mouth. The midline incision is made just above the inferior labial frenulum with a scalpel as preferred by our group to avoid the risk of lip burn. The other two incisions are made just medial to the the vermillion border near the labial commissure and measures less than 5-mm in length. Chai et al., moved these two incisions lateral/posterior from the canine teeth which have been attributed to less mental nerve injury and tearing of the lip commissures (51).

Recently, our group has also detailed the use of IONM during TOETVA (52). This is performed through a FDA-approved, single use, 230 mm monopolar probe with a ball tip, connected to the IONM system. This allows the surgeon to identify and evaluate the status of the vagus, recurrent laryngeal, and superior laryngeal nerves without any additional incisions. IONM allows active monitoring during thyroid retraction and dissection. Moreover, it enables ipsilateral RLN evaluation prior to proceeding with contralateral lobectomy during a total thyroidectomy. IONM potential limitations associated with use are its costs, the need for intraoperative instrument exchange, and probe availability and disposability. Despite this, IONM increases the confidence of surgeons to perform TOETVA safely, and is strongly encouraged by our group.

For the robotic technique, surgeons may utilize an additional axillary incision to insert the fourth robotic arm for counter-traction and drain insertion if needed. Though it is useful, this contradicts the cutaneous “scarless” principle of the transoral surgery that made our group less enthusiastic about employing the current robotic surgical systems for the transoral thyroid surgery.

Outcomes, limitations and potential complications

Outcomes

Our group has recently performed an analysis to determine outcomes of 689 TOETVA patients (34) who have undergone isthmusectomy, lobectomy, subtotal thyroidectomy, or total thyroidectomy, with and without central neck dissection. Of these 689 cases, 683 (99%) were completed without conversion. Those converted to an open approach were due to uncontrolled bleeding (five cases) and excessive tumor size with evidence of pretracheal nodal metastasis (one case). No published cases of permanent RLN injury, permanent hypoparathyroidism, CO2 embolism, permanent mental nerve injury with TOETVA, with only one hematoma (0.1%) reported. The transoral approach to the neck is classified as ‘clean-contaminated’ surgery and carries an inherently greater risk of infection than clean transcervical thyroidectomy. However, only one case of neck infection (0.1%) has been reported. Other complications include reported oral commissure tears and three cases (0.4%) of skin flap burn. Moreover, TOETVA patients had decreased postoperative pain compared with patients undergoing transcervical thyroidectomy in one series (32). No significant difference in length of stay has been described (32).

Limitations

Similar to other novel surgical techniques, transoral vestibular approach surgery is limited by increased operating time, a notable but reasonable learning curve, unique complications (generally minor, as above), and rigid patient selection criteria. (TOET/PVA) has significantly longer operative times than the conventional transcervical technique in all described case series, perhaps due to port placement and flap dissection (43). The largest series by Anuwong et al. (32) reported significant differences in mean operative times of 78.6 versus 64.2 minutes for lobectomy via TOETVA and the open approach, respectively, and 135.1 versus 103.3 minutes for total thyroidectomy via TOETVA than the open approach, respectively.

The experience with TOEPVA has been more limited than TOETVA thus far. Sasanakietkul et al.’s 12-patient series from Thailand demonstrated the safety of the procedure while achieving biochemical cure of primary hyperparathyroidism without major complications (53). One temporary recurrent laryngeal neve palsy was reported. Our group has presented our experience with more than 20 cases (54).

Potential complications

Novel complications associated with transoral vestibular approach surgery include mental nerve injury, chin flap perforation, and oral commissure or inferior labial frenulum tear. Revised positions of vestibular incisions to decrease the incidence of nerve injury have been implemented in some series. Previous reports of the transoral vestibular approach documented a high complication rate (15.6–100%) for mental nerve injury with use of the robotic-assisted technique due to the 5 mm incisions in close proximity to the center incisions (16,55,56). Since then, both 5 mm incisions have been relocated, allowing for greater mobility of the lip and decreasing tension on the mental nerve where it exits the mental foramen.

Discussion and future directions

Transoral vestibular approach central neck surgery has emerged as a solution for patients who wish to avoid any cutaneous incision (Figure 1). Even as scrutiny of novel operative techniques and the effects that new technologies have on patient outcomes has increased, TOETVA and TOEPVA has spread rapidly as an alternative to open thyroidectomy and other remote-access thyroidectomy techniques.

Figure 1 A 31-year-old woman (A) and a 56-year-old man (B) 3 weeks after TOETVA.

Still as relatively novel surgical techniques, TOETVA and TOEPVA will likely continue to gain traction as their utilization increases and surgeons become more accustomed and experienced with the techniques. With increased operative use and surgeon experience with this approach, the gap in conventional outcomes between TOETVA and the transcervical approach will likely continue to narrow, with both operative time and the incidence of TOETVA-specific complications diminishing.

Furthermore, with the development of the new da Vinci single-port robotic system, additional cutaneous incision for an additional surgical arm may no longer be necessary in robotic surgery. Hence, the transoral vestibular approach may be further augmented with robotic surgery to achieve a truly scarless technique that enhances surgical dexterity and subjective surgical performance without compromising the improved cosmesis of TOETVA and TOEPVA (57). Currently, the large size of the central port has limited utilization to some degree.

With increasing experience and utilization of TOETVA and TOEPVA may come expanding indications for other thyroid and parathyroid pathologies. Eligibility criteria for a transoral vestibular approach have continued to expand to include use in well-differentiated thyroid carcinomas, thyroglossal duct cysts, Graves’ disease, and sex-affirming chondrolaryngoplasty. Nevertheless, careful adoption is crucial for successful implementation as premature implementation can increase the rate of conversion and hence abandonment of the new technique—and all it has to offer (42).

Although the development and implementation of a transoral vestibular approach for these surgeries may have high initial costs, the payoffs—potential for increased cosmesis, decreased pain, and improved quality-of-life—may mark the next horizon for surgical operative innovation in the neck.

Conclusions

TOET/PVA is the only surgical technique for thyroid and parathyroid surgery that does not have any cutaneous incision. The rapid adoption to date suggests that further gains may be forthcoming. Future studies are necessary to demonstrate the long-term value of the approach.

Acknowledgments

The authors thank Emerson Lee for technical help and language editing assistance.

Funding: None.

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/gs.2020.03.05). Dr. Tufano reports personal fees from Medtronics, personal fees from Hemostatix, outside the submitted work. RTP serves as the unpaid editorial board member of Gland Surgery from Sep 2018 to Aug 2020. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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