Transoral and submental thyroidectomy using intraoperative nerve stimulation and indocyanin green fluorescence imaging

Abstract

There is a recent proliferation of clinical studies about the minimally invasive scarless thyroid surgery. The transoral endoscopic thyroidectomy vestibular approach (TOETVA) carries a great potential for being scarless surgery via a short dissection flap. However, TOETVA has limitations in extracting larger thyroid tumours via the transoral vestibular incision and due to its potential damage to the branches of the mental nerve. The rapidly evolving surgical innovations have now introduced transoral and submental thyroidectomy (TOaST) approach that allows extraction of large thyroid tumours with less flap dissection and minimal postoperative pain. We present a 39-year-old man with a large multinodular goitre. The patient was euthyroid with moderate to severe compression symptoms of difficulty in breathing and swallowing. We performed a TOaST procedure using intraoperative neuromonitoring and indocyanin green fluorescence imaging with an uneventful recovery. This is a first case report from the middle east region that will pave the way to large clinical trials to determine the efficacy and safety of TOaST.

Background

In the recent past, endoscopic thyroid surgery has gained a universal popularity. This is essentially driven by a paradigm shift towards the minimally invasive surgery, which is further complemented by patient-led cosmetic preferences. Since the introduction of first endoscopic thyroid surgery by Hüscher et al,¹ a plethora of clinical studies have reported the safety and feasibility of the minimally invasive approach, which replaces the anterior cervical incision with other anatomical locations such as axillobreast,² retroauricular³ or transoral endoscopic thyroidectomy vestibular approach (TOETVA).⁴ Of these approaches, TOETVA is preferred by most endocrine surgeons due to a shorter operating time taken for the creation of an adequate working space.⁵ In addition, TOETVA offers a completely scarless surgery which adds value to its profile for safety and effectiveness.

Unfortunately, a host of clinical trials has shown several pitfalls of TOETVA^{6 7}; a transient or permanent cutaneous numbness of the lower jaw or a permanent cutaneous paralysis of the midline chin due to injury to a branch of the mental nerve by incision in the central oral vestibule.⁷ Furthermore, creation of the working space through a vestibular approach is technically demanding and time-consuming. Lastly, the extraction of the thyroid gland is limited up to a size of 4 cm by TOETVA. In order to circumvent these limitations of TOETVA, recently, a transoral and submental thyroidectomy (TOaST) has been introduced as a compelling and attractive alternative.⁸ In TOaST, the telescope trocar is placed in the submental region, which potentially prevents damage to the mental nerve branches with less sensory impairment of the chin. At the same time, TOaST approach facilitates extraction of larger tumours and has been shown to have a short operating time, small area of surgical dissection and subsequently reduced postoperative pain.⁹

This case report presents a distinct surgical procedure of TOaST performed in an adult male with a successful outcome. To our knowledge, we are reporting the first case of TOaST from the middle east region.

Case presentation

A 39-year-old man, otherwise healthy, presented to the surgical clinic of Zulekha Hospital Sharjah United Arab Emirates (UAE) with a thyroid goitre since 9 years. Zulekha Hospital Sharjah is a 161-bedded acute-care teaching hospital, affiliated with the College of Medicine University of Sharjah UAE. The patient had a family history of papillary cell carcinoma of the thyroid in his first and second degree relatives. He was initially concerned about the size of the goitre, but as time elapsed, he experienced compression symptoms by the goitre such as difficulty in breathing and disturbed sleep. On the examination, there were no constitutional findings. There was a soft and nodular thyroid goitre involving both lobes. There was no cervical lymphadenopathy.

Investigations

All preoperative labs including T3, T4, TSH, serum calcium and parathyroid hormone levels were within normal limits. An X-ray of the neck and chest showed a tracheal deviation towards the right side (figure 1).

Figure 1.

A preoperative X-ray of the chest and abdomen showing tracheal deviation towards right side due to the thyroid goitre.

An ultrasound of the neck showed a 5.5×4 cm left lobe and a 5.5×2 cm right lobe of the thyroid. A large heterogeneous nodule measuring 36.3×28.1 mm with solid and cystic components and lucent margin was noted in the left lobe. A preoperative ultrasound-guided FNAC of the left-sided thyroid nodule showed a benign follicular hyperplasia, Bethesda system category 2. Due to the compression symptoms and patient’s concerns, a decision of total thyroidectomy was taken. A TOaST approach was planned due to a large goitre as the specimen retrieval was deemed easier than in the TOETVA approach. An informed consent was taken from the patient for publication of this case report.

Treatment

Surgical technique

Using general anaesthesia and orotracheal intubation, the patient was placed in a supine and Trendelenburg’s position with neck extension. A long needle was used for the subcutaneous infiltration of neck tissues with 1:50 000 dilution of epinephrine prepared in 500 mL of normal saline. This step facilitates the creation of a surgical plane and helps to control intraoperative bleeding. A 3 cm submental midline incision was made two fingers below the chin and the operative site was opened with blunt dissection. A bladeless 12 mm laparoscopic port was inserted through the submental incision. Then two short 5 mm pyramid tip ports were inserted into the lower lip at the vestibular region at the junction between the canine and the first premolar tooth on each side. The placement of ports through these anatomical landmarks avoids damage to the mental nerve. We used a 12 mm 30° camera with indocyanine green (ICG) infrared scope. An intracervical pressure was maintained at 7–8 mm Hg using a continuous CO₂ insufflator. A harmonic scalpel was used for the dissection of the anatomical plane up to the sternal notch inferiorly and up to the lateral borders of the sternocleidomastoid muscles on each side. The strap muscles were divided in the midline and were then retracted laterally via a transcutaneous 2/0 silk suture. The thyroid isthmus was also incised in the midline. Later, the superior thyroid vessels were dissected and divided between clips. Finally, the thyroid lobe was mobilised and the recurrent laryngeal nerve (RLN) was identified and preserved. All steps of TOaST are illustrated in figure 2.

Figure 2.

Surgical steps of transoral and submental total thyroidectomy. (A) placements of trocars in the submental and transoral vestibular positions, (B) opening of the isthmus in the midline, (C) the dissection of the right superior thyroid artery, (D) dissection and mobilisation of the left thyroid lobe from the trachea, (E) the right recurrent laryngeal nerve being tested with nerve stimulator, (F) ICG view of the right parathyroid gland and recurrent laryngeal nerve, (G) lateral dissection of the left thyroid lobe with exposed left inferior thyroid vessels, (H) placement of the left thyroid lobe in endobag. ICG, indocyanine green.

We routinely used specially designed long probe nerve stimulators for the identification of the RLN and the superior laryngeal nerve. When used directly over the nerve, 1 mA current was used, while a stronger current of up to 5 mA was applied to locate the nerve that was surrounded by tissues (figure 3).

Figure 3.

The recurrent laryngeal nerve stimulation tracings during the pre-and-post left lobectomy during the transoral and submental total thyroidectomy.

Additionally, we used ICG fluorescence imaging to confirm the location of the superior and inferior parathyroid glands as shown in figure 2. A post-thyroidectomy ICG-visualisation was carried out to confirm the viability of the RLN and parathyroid glands. The use of a nerve stimulator and an intraoperative ICG fluorescence imaging significantly enhanced the safety profile of the TOaST procedure. Since a total thyroidectomy was planned, the other lobe was similarly dissected. The dissected thyroid gland was divided into two lobes and each lobe was separately removed via the 12 mm port. After securing haemostasis, an oxidised cellulose polymer agent was sprinkled over the surgical field and the strap muscles were approximated in the midline using absorbable sutures. A gravity drain was placed in the neck and the submental and the vestibular incisions were closed with absorbable sutures. A pressure dressing in the form of a face band covering the submental area and the upper part of the neck was applied for 48 hours. The total operative time was 137 min and the estimated blood loss was less than 20 mL.

Outcome and follow-up

Postoperative care

A prophylactic intravenous cephalosporin was given an hour before the procedure and then the same antibiotic was continued intravenously for the next 2 days. Later, the patient was given oral antibiotics for next 5 days. The patient received two tablets of mefenamic acid 500 mg three times a day. A liquid diet was started 6 hours after surgery. There was no symptoms of RLN injury and labs showed normal serum calcium and parathyroid levels postoperatively. The histopathology report showed a multinodular goitre in both lobes of the thyroid gland with cystic degeneration and fibrosis without malignancy. The patient had an uneventful recovery and was discharged home on the third post-operative day with a plan for a follow-up visit after a week. During the subsequent follow-up visits on weeks 3 and 4, there was no evidence of hypoparathyroidism or RLN injury (figure 4).

Figure 4.

A 3-week postoperative view of the patient’s oral cavity and external profiles.

Discussion

This case report illustrates a successful outcome of TOaST for a large multinodular goitre. Our patient had an uneventful recovery and did not experience chin numbness or mental nerve injury postoperatively. Avoidance of the nerve injury essentially results from a short tissue flap and keeping a safe distance from the branches of the mental nerve. Investigators have reported high rates of mental nerve injury during transoral thyroidectomy.⁷ TOETVA aims to scale down the damage to the main mental nerve by limiting the length of the midline intraoral incision, by a careful creation of the premandibular subcutaneous flap and by making 5 mm incisions close to the free edge of the lower lip besides the canines.¹⁰ In TOaST, a submental incision practically eliminates the need for a premandibular dissection without any possibility of damage to the midline branches of the mental nerve. Perigli et al have also reported a similar procedure of a hybrid transoral endoscopic thyroidectomy with a submental approach.¹¹ The authors have reaffirmed the avoidance of the mental nerve injury which is essentially caused by the tissue distraction via the central vestibular route. A major step during the transoral thyroidectomy is the creation of the working space by a wide range of techniques. We used a long needle for the subcutaneous infiltration of the neck tissues with 1:50 000 dilution of epinephrine prepared in 500 mL of normal saline. This step not only creates a working space but also secures homeostasis of the surgical field. Interestingly, Liang et al, have reported a sequential use of the balloon of the Foley’s catheter for the creation of a subplatysmal tunnel from the chin up to the sternal notch during transoral thyroidectomy.¹² On the other hand, Müller et al have described the results of a new variant of transoral thyroidectomy where they used hydrodissection of the subplatysmal space with a rounded tip with less bleeding and seroma formation.¹³ All techniques for the creation of working space in transoral thyroidectomy are feasible and have shown promising results.

As evident from our case, a submental route is feasible for the extraction of a large thyroid gland without its disruption and damage to the capsule. The extraction of an intact gland is paramount in follicular lesions as a complete tumour capsule is essential for the histological evidence of capsular invasion in malignancy.¹⁴ In contrast, during TOETVA, thyroid tumours larger than 4 cm often necessitate disruption of the capsule and disintegration of the gland for its extraction through the 10 mm central port.⁹ Such manoeuvres, particularly when performed for malignant lesions, can potentially lead to tumour seedling inside the neck. The scope of the extension of the transoral vestibular incision is limited, as a large incision would certainly damage the central branches of the mental nerve with an associated subcutaneous chin numbness and paralysis.

By and large, in open and minimally invasive thyroid surgery, transient RLN paralysis has been reported in 5%–8% of cases, while a permanent paralysis occurs in 0.3%–3%.¹⁵ Some authors have argued that, in TOaST and even in TOETVA, the use of endoscopic rigid instruments allow only linear movements, which incapacitates the surgeons to carry out their natural motor skills.¹⁶ Similarly, the use of two-dimensional endoscopic cameras further limits the range of the surgical field. To circumvent these limitations, Fu et al, have proposed key surgical steps that can prevent injury to the RLN during transoral approach; a routine use of intraoperative nerve monitoring and stimulation, keeping the working forceps at least 3 mm away from the RLN, and to avoid overstretching of the RLN.¹⁷ During TOaST, we used intraoperative nerve stimulator during and post-thyroidectomy. Intraoperative neuromonitoring has been shown to play a vital role in preventing total, transient and permanent injury of the RLN during thyroidentomy.¹⁸ Using intraoperative neuromonitoring during thyroidectomy on 425 patients, Gür et al have argued that this technique allowed the surgeon to detect the RLN injury intraoperatively and to modify the surgical plan to avoid bilateral vocal cord paralysis.¹⁹ Likewise, several studies have reported the successful use of ICG fluorescence in endocrine surgery for the evaluation of the viability of parathyroid glands after thyroidectomy and to localise parathyroids during the surgery.^{20 21} Unfortunately, there is no standard dosage or protocol for the use of intraoperative ICG. Nevertheless, the routine use of ICG fluorescence certainly enhances surgeon’s decision-making for the safe progression of the surgical procedure.

There is a concrete evidence that surgical coaching²² using modern state-of-the-art technological tools²³ can minimise the rate of surgical complications and can enhance trainees’ skills and competence. Regardless of the surgical access and body system, the core principles of surgical practice for benign and malignant lesions remain the same.^{24 25} Concerning the transoral thyroidectomy, Russell et al., have eluded that even a higher BMI was not associated with a greater likelihood of complications compared with the conventional open transcervical thyroidectomy.^26–28 This offers a wider scope of patients’ demographics who can benefit from the transoral approach. From another novel perspective, You et al., have reported no significant difference in complications between open and transoral robotic thyroidectomy (TORT).²⁹ The researchers have argued that the surgeons experienced in thyroid and robotic surgery can perform TORT with a sound safety profile and effectiveness. The optics of thyroid surgical technologies have significantly evolved from open to TOEVT and to TORT and there is a great potential towards a more cosmetic-driven, safe, effective and scarless surgical realm.

One limitation of the TOaST procedure is its inability to offer a completely scarless surgical outcome. From another perspective, TOaST is more suitable for patients with pointed chins or long moustache, which will potentially cover the submental surgical scar with a better cosmesis.³⁰ Transoral thyroidectomy is not without complications. Kim et al have reported a rare but a serious complication of transoral endoscopic thyroidectomy with carbon dioxide embolism due to a laceration of the anterior jugular vein during the dissection of the skin flap.³¹

Conclusion

This case report presents a successful outcome of the TOaST procedure for a large multinodular thyroid goitre. Though promising and feasible, large-scale clinical studies are essential to validate the safety profile and effectiveness of TOaST for benign and malignant thyroid lesions.

Patient’s perspectives.

I noticed a swelling in the neck since 9 years. In the presence of a family history of thyroid cancer, I was extremely distressed. This adversely affected my psychosocial life. Additionally, I was worried about the obviously apparent neck swelling, which used to make me shy and depressed. Lastly, I was concerned about the surgical scar if the surgery was done through a conventional open approach. Therefore, I had detailed consultations with the surgical team and which offered the possibility of a minimally invasive thyroid surgery. In view of the enormous size of the thyroid goitre, a TOEVT was not possible and a TOaST approach was coined. I accepted this strategy and had an uneventful course in the hospital.

I had an uneventful postoperative recovery without much pain and worries. In addition, I was able to eat and drink on the same day of surgery that encouraged me to move out of the bed. In the presence of minimal pain and the liberty to talk, I was able to communicate with his family and healthcare professionals. This element incredibly motivated me in pursuing a fast postoperative recovery.

Sometime after discharge, I was interviewed about the quality of life (QoL) using a validated SF-36 QoL questionnaire.³² This tool contains seven components and the patient’s responses to each item on a likert’s scale of one to five about the QoL after TOaST showed a cumulative average of 4.5 out of 5; physical function (4/5), bodily pain (4/5), general health (4/5), vitality (5/5), social function (5/5), role emotion (5/5) and mental health (5/5). From the patient’s perspective, the degree and speed of improvement was beyond my expectations and since I naturally grow beard, the submental scar was nor visible and I perceive to have a scarless thyroid surgery.

Learning points.

• Minimally invasive scarless thyroid surgery has gained popularity due to superior cosmetic results and safety profile.

• The transoral endoscopic thyroidectomy vestibular approach (TOETVA) offers a direct access to the thyroid gland without an obvious scar.

• TOETVA cannot be used for large nodules.

• The transoral and submental thyroidectomy approach allows the extraction of large tumours with less flap dissection and minimal postoperative pain.

Ethics statements

Patient consent for publication

Obtained.