Since Theodor Kocher reduced the mortality rate of thyroidectomy from the 40% reported by Billroth to 0.2% in 1895, a collar incision with open removal of the thyroid gland is the standard procedure [1, 2]. In the past decade, efforts were made to reduce incision size and surgical access trauma by the use of endoscopic techniques. A first attempt was replacement of the central “Kocher incision” with lateral neck incisions and endoscopic removal of a thyroid lobe by Hüscher on 8 July 1996 . This lateral access was limited to removing only one lobe of the gland. The most common technique to date is the one developed by Miccoli et al. . These authors reduced the incision to a size of 20 to 25 mm and operated on the thyroid by the use of video-endoscopic assistance (MIVAT).
Several groups have described an access outside the frontal neck region via a chest [5–8], axillary , or combined axillary bilateral breast approach . These accesses only moved the entry point from the frontal neck region to other regions, where they are still visible. The aforementioned minimally invasive approach and the conventional open approach do not respect anatomically given surgical planes and may therefore result in patient complaints, especially swallowing disorders after the scaring of the subcutaneous tissues. These extracervical approaches are associated with an extensive dissection in the access area and thus are maximally invasive.
Therefore, we developed an exclusively endoscopic approach for thyroid resection  with standard instruments used for minimally invasive surgery (diameter, 3.5 mm). This endoscopic minimally invasive thyroidectomy (eMIT) technique was evaluated carefully by anatomic and cadaver dissections as well as ultrasound studies for technical realization and needs for instrument design . To verify the safety and feasibility of the method, an animal trial was conducted in August 2008. Surgery was performed securely on five pigs, with very low blood loss. The postoperative behavior with special regard for feeding and pain reaction was normal until dissection. Especially, no local infection in the oral cavity or cervical spaces was noted.
All the trials of eMIT showed good results, so we went on to its first clinical application in the spring of 2009. A 53-year-old man had experienced dysphagia for more than a year. During routine diagnosis, the thyroid hormones T3, T4, and TSH were controlled and within normal levels. Thyroid scintigraphy, B-mode ultrasound examination, and laryngoscopy were performed preoperatively. An euthyroid nodular chance of the right hemithyroid with a beginning focal autonomy was diagnosed. After the patient’s informed consent was received, surgery was performed on 18 March 2009 in an interdisciplinary collaboration between a general surgeon and a head and neck surgeon.
The first incision was made in the midline sublingually. A 5-mm trocar was directed through the floor of the mouth muscles into the subplatysmal layer and positioned at the level of the cricoid. Carbon dioxide then was insufflated at 6 mmHg to build a tent above the thyroid gland. Next, a second trocar for insertion of the surgical instruments was placed over a vestibular incision into the same subplatysmal layer. This allowed the surgical field to be visualized fully and dissected with 3.7-mm standard minimally-invasive instruments. A third trocar for surgical instruments then was placed through an incision on the left side of the vestibule of the mouth.
After a midline incision of the linea alba, the fibrous capsule of the thyroid gland could been seen. The isthmus then was prepared in total. Next, the strap muscles above the right hemithyroid were prepared, showing the right upper pole. With the Harmonic scalpel, the isthmus was divided on the left side. The gland was loosened from the trachea and the adjacent lamella. The vessels of the upper pole were divided by Ultracision (Ethicon-Endosurgery, Cincinnate/Ohio, USA). Under the adjacent lamella, the recurrent nerve was visualized and stimulated. Neuro-monitoring showed an intact function of the nerve. Finally, the lower pole was detached, allowing the thyroid to be freely movable.
Recovery of the tumor was performed through the median trocar incision after the optic device was moved through a lateral trocar. The tumor volume was 5.5 ml. The operation site was checked for bleedings and lavaged with sodium chloride. After removal of all the trocars, the wounds were sutured with self-resorbable sutures. Plaster tape was applied for 24 h. No direct postoperative complications occurred. Postoperative histology showed a colloidal struma.
The floor of the mouth healed well, with no local infections at the incision sites or in the cervical spaces. Vocal cord function, evaluated by direct video-laryngoscopy, was normal. The patient had minimal swelling of the neck and a small hematoma, which resolved within 2 weeks. He had neither swallowing disorders nor oral pain. His preoperative dysphagia was gone, and he left the clinic 2 days after surgery without any complaints.
With the development of an exclusively endoscopic approach for thyroid resection (eMIT) and its first clinical application, we could show the safety and feasibility of another natural orifice surgery procedure. One major concern before surgery was possible infection of the cervical spaces by introduction of oral flora to these regions. Investigating this infection risk, Hong and Yang  evaluated the surgical results associated with the intraoral approach for submandibulectomy in a series of 77 cases of chronic sialadenitis and benign mixed tumors. The infection rate was 2.6% (2 patients) compared with 7.3% in a control group of 251 patients who underwent a transcervical procedure . Therefore, we estimated the infection risk to be lower than with conventional transcervical approaches.
The clear advantages of this technique are its minimally invasive character, its reduction of surgical trauma, its direct access to surgical planes and spaces, its avoidance of swallowing disorders and postoperative dysphagia, and finally, its avoidance of any skin scars. Further trials are already being conducted.
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Wilhelm, T., Metzig, A. Endoscopic minimally invasive thyroidectomy: first clinical experience. Surg Endosc 24, 1757–1758 (2010). https://doi.org/10.1007/s00464-009-0820-9
- Thyroid Resection
- Vocal Cord Function
- Conventional Open Approach
- Adjacent Lamella
- Chronic Sialadenitis