RU2800313C1 - Method of surgical treatment of thyroid cancer with metastases to the lymph nodes of the central tissue of the neck - Google Patents

Abstract

FIELD: medicine; surgery; oncology.

SUBSTANCE: surgical access is provided. Sequentially, first from one side, and then from the contralateral side, the sternothyroid muscle is dissected in the area of attachment to the thyroid cartilage, the muscle branches of the anterior branch of the superior thyroid artery are ligated. Then the upper pole of the thyroid lobe is separated from the lower constrictor of the pharynx, and in this space below the line of attachment of the sternothyroid muscle to the thyroid cartilage, the external branch of the superior laryngeal nerve is identified. After that, the anterior branch of the superior thyroid artery is selectively ligated. The visceral sheet of the internal fascia of the neck is opened at the superior aspect of Berry's ligament with precision preservation of the posterior branches of the superior thyroid artery and its anastomoses with the branches of the inferior thyroid artery. At the same time, this zone is inspected posteriorly to the esophagus to detect the upper parathyroid glands. After ligation of the inferior branch of the inferior thyroid artery, the isthmus of the thyroid gland is crossed. Further, alternately from the lateral, and then from the medial side, approaching the tubercle of Zuckerkandl, the vascular pedicle of the thyroid gland is formed with precise isolation and preservation of the anterior extralaryngeal branch of the recurrent laryngeal nerve. Extirpation of the lobe of the thyroid gland is performed. After that, a revision of the central tissue of the neck to the thymus is carried out with visualization of the mediastinal branches of the inferior thyroid artery or branches of the unpaired thyroid artery. If parathyroid glands are detected, ipsilateral central lymph node dissection is performed with preservation of the parathyroid glands and their vessels. Then the entire sequence of actions is carried out from the contralateral side.

EFFECT: method improves the results of surgical treatment of thyroid cancer with metastases in the central tissue of the neck, reduces the risk of postoperative complications, improves the quality of life of patients, and prevents severe chronic diseases in the late postoperative period.

1 cl, 7 dwg, 1 ex

Description

The invention relates to medicine, namely to surgery, oncology, and can be used for the surgical treatment of patients with thyroid cancer with metastases to the lymph nodes of the neck.

Over the past two decades, the results of epidemiological studies indicate a steady increase in the incidence of thyroid cancer, which leads to a natural increase in the number of surgical interventions on the organ. Despite significant technical advances, complications after surgical interventions on the thyroid gland are quite common.

The most common complication is postoperative hypoparathyroidism, primarily due to impaired blood supply to the parathyroid glands and, less frequently, to their accidental removal. Thus, transient hypoparathyroidism after thyroidectomy with central cervical lymph node dissection can reach 60% of cases, permanent - 16%. Acute severe manifestations of hypoparathyroidism are characterized by a violation of the sensitivity of the limbs, local and generalized convulsions, which can lead to a life-threatening consequence - laryngospasm. Chronic forms of the disease that occur in the late postoperative period significantly reduce the patient's quality of life due to daily paresthesias, convulsions and the need for constant medication, lead to calcification of the basal ganglia of the brain, nephrocalcinosis and cataracts.

Despite the use of new approaches in the technique of surgery, the use of modern equipment, laryngeal paresis is not a casuistic complication and is diagnosed on average in 9.8% of patients after surgical interventions on the thyroid gland.

For most surgeons, the external branch of the superior laryngeal nerve, which is involved in the innervation of m. cricothyroideus, which provides tension to the vocal folds. Therefore, in 58% of cases, especially with a high location of the upper pole of the thyroid gland, this structure is damaged. With damage to the nerve branch, the patient is associated with the inability to produce high-frequency sounds, “fatigue” of the voice, and choking on liquid food.

There is a known method of surgical treatment of patients with thyroid cancer with metastases to the lymph nodes of the neck (RF Patent 2616763, IPC A61B 17/00, publ. 2017), including access, complete extrafascial removal of the thyroid gland and neck tissue with lymph nodes. During the operation, the prevention of damage to the upper and recurrent laryngeal nerves is carried out with a precision technique of ligation of vessels as close as possible to the thyroid capsule, neuromyography is used. To visualize the parathyroid glands, a “stress test” is used, which consists in periodically lightly tapping the tip of a surgical instrument on the anatomical structures in the surgical field. By darkening or the appearance of hyperemia with an injection of blood vessels, the parathyroid glands are identified from the lobules of fatty tissue and lymph nodes. After that, the branches of the lower thyroid vessels are separately ligated at the thyroid capsule.

The main disadvantage of this method is the lack of control of the vascular architectonics of the thyroid gland throughout, which can lead to impaired blood supply or removal of the parathyroid glands along with the central fatty tissue, and, as a consequence, the development of postoperative hypoparathyroidism. The use of a "stress test" and even slight traction of the parathyroid glands can lead to rupture of the arterioles of the feeding pedicle and devascularization of the structures. Another disadvantage of this method is the lack of routine visualization of the external branch of the superior laryngeal nerve, which can lead to nerve damage, especially with an increase in the proportion of the thyroid gland and a change in the syntopy of organs. Another drawback of the method is the constant traction effect on the recurrent laryngeal nerve due to the tension of the lobe anteriorly and medially, which can cause neuropraxia of the nerve and cause paresis of the larynx.

There is a known method for removing the thyroid gland (RF Patent 2772015 IPC A61V 17/00, publ. 2022), in which the thyroid lobe is mobilized from the trachea after crossing the isthmus by dissecting the Berry ligament. The function of the laryngeal nerves is monitored by comparing the function of the vagus and recurrent laryngeal nerves before and after surgery using intraoperative neuromonitoring. At the same time, the branches of the inferior thyroid artery and vein are crossed with the mobilization of the thyroid lobe from the trachea. A lateral abduction of the mobilized thyroid lobe is performed, in the absence of traction of the lobe in the medial direction during the entire operation. Further, after separation of the lobe from the trachea and lower thyroid vessels, the recurrent laryngeal nerve, vessels of the upper and lower parathyroid glands are sequentially isolated from the medial side of the thyroid lobe. After mobilization of the parathyroid glands, the lower pole of the lobe is brought out into the surgical wound. At the last stage of the operation, the vessels of the upper pole of the thyroid lobe are crossed.

A significant disadvantage of the proposed method is its limited use only for "comfortable" thyroid gland, when the Berry ligament is long and soft elastic. In the case of an individual feature, chronic autoimmune thyroidin with a periprocess, diffuse toxic goiter, recurrent nodular goiter, carcinoma located in the area of the tubercle of Zuckerkandl, the ligament is significantly thickened (scarred) and shortened, which significantly complicates the work in this area, where the recurrent laryngeal nerve “pulled up” by the fibrous process is located in close proximity, the vessels supplying the upper parathyroid gland prominent glands, and the risks of damage to these structures increase. In addition, such access to the thyroid lobe additionally increases the risks of postoperative hypoparathyroidism when the parathyroid glands are located on the lateral surface of the thyroid lobe and when performing central cervical lymph node dissection, since it does not allow a complete revision of the surrounding tissues to visualize all the parathyroid glands and their arterial structures.

As a prototype, a method of thyroidectomy was chosen, which can be used to treat patients with benign and malignant tumors of the thyroid gland, as well as with metastases to the lymph nodes of the central tissue of the neck (RF Patent 2285452 IPC A61B 17/00, publ. 2002), including access, isolation of the superior thyroid artery, mobilization of the unaffected lobe of the thyroid gland from the lateral side and dislocation it into the wound medially and anteriorly, visualization of the recurrent laryngeal nerve and tracing it to the place where it flows into the larynx, isolation of the inferior thyroid artery at the intersection with the recurrent laryngeal nerve and tracing the artery and its branches to the capsule of the thyroid gland, visualization of the parathyroid glands in this area, after which the branches of the inferior thyroid artery are ligated, the central fatty tissue of the neck with lymph nodes is removed. Ligation of the branches of the inferior thyroid artery is carried out intracapsularly, 4-5 mm away from the place of confluence by notching the thyroid capsule, which is then sutured over the ligated vessels (extracapsular removal of the unaffected lobe). The proportion affected by the tumor process, together with the isthmus, is removed by an extrafascial method.

Significant disadvantages of this method are the high risk of developing postoperative hypoparathyroidism, since the branches of the superior thyroid artery are non-selectively ligated, there is no revision of the central tissue of the neck, in which both lower and supernumerary parathyroid glands can be located, the tumor-affected lobe is removed extrafascially without precise isolation of vascular structures and parathyroid glands. Also, the disadvantage of this method is a decrease in the radicalness of the surgical intervention due to the preservation of the portion of the thyroid capsule in the area where the branches of the inferior thyroid artery flow into, which is fraught with the abandonment of the thyroid tissue and the need for subsequent radioiodine ablation. In addition, there is a high probability of developing dysphonia or paresis of the larynx in patients, due to the lack of visual control of the external branch of the superior laryngeal nerve and prolonged traction of the recurrent laryngeal nerve when the lobe is pulled anteriorly and medially.

The objective of our proposed method is to eliminate these shortcomings by increasing the efficiency of surgical intervention by reducing the likelihood of postoperative complications such as hypoparathyroidism, laryngeal paresis and dysphagia, while increasing the radicalness of the operation.

To solve the problem in the surgical treatment of thyroid cancer with metastases to the lymph nodes of the central tissue of the neck, including access, isolation of the superior thyroid artery, mobilization of the thyroid gland lobes from the lateral side and dislocation of them medially and anteriorly into the wound, visualization of the recurrent laryngeal nerves and tracing them to the place where they flow into the larynx, isolating the inferior thyroid arteries at the intersection with the recurrent laryngeal nerves and tracing the arteries and their branches to the capsule of the thyroid gland, visualization of the parathyroid glands in these areas, ligation of the branches of the lower thyroid arteries, thyroidectomy, removal of the central adipose tissue of the neck with lymph nodes, it is proposed after making access sequentially, first from one side, and then from the contralateral side: dissect the sternothyroid muscle in the area of attachment to the thyroid cartilage, ligate the muscle branches of the anterior branch of the superior thyroid artery. Then, the upper pole of the thyroid lobe is separated from the lower pharyngeal constrictor, and in this space below the line of attachment of the sternothyroid muscle to the thyroid cartilage, the external branch of the superior laryngeal nerve is identified. After that, selectively ligate the anterior branch of the superior thyroid artery; open the visceral sheet of the internal fascia of the neck at the upper aspect of the ligament of Berry with precision preservation of the posterior branches of the superior thyroid artery and its anastomoses with the branches of the inferior thyroid artery. At the same time, conduct an audit of this zone posteriorly to the esophagus in order to detect the upper parathyroid glands. After ligation of the lower branch of the inferior thyroid artery, cross the isthmus of the thyroid gland, and then alternately from the lateral and then the medial side, approaching the tubercle of Zuckerkandl, form the vascular pedicle of the thyroid gland, with precise isolation and preservation of the anterior extralaryngeal branch of the recurrent laryngeal nerve, perform extirpation of the thyroid lobe. After that, a revision of the central tissue of the neck to the thymus is carried out with visualization of the mediastinal branches of the inferior thyroid artery or branches of the unpaired thyroid artery and, if parathyroid glands are detected, ipsilateral central lymph node dissection is performed while preserving the parathyroid glands and their vessels. Then the entire sequence of actions is carried out from the contralateral side.

The technical result of the proposed method is the maximum ablation of tissues in thyroid cancer with metastases to the lymph nodes of the central tissue of the neck with the preservation of vital structures due to in situ visualization of the largest number of parathyroid glands and their blood supply, precise selection of the external branches of the upper laryngeal nerves and all extralaryngeal branches of the recurrent laryngeal nerves.

In FIG. 1 shows the initial stage of mobilization of the upper pole of the thyroid lobe, the short muscular branches of the anterior branch of the superior thyroid artery are stretched (all figures show the left lobe of the thyroid gland in a horizontal position); in fig. 2 - the anterior branch of the superior thyroid artery was crossed, the external branch of the superior laryngeal nerve was visualized; in fig. 3 - the visceral sheet of the internal fascia of the neck is opened at the upper aspect of the Berry's ligament, the upper parathyroid gland is visualized; in fig. 4 - the left lobe of the thyroid gland is dislocated, the intersection of the recurrent laryngeal nerve and the inferior thyroid artery is visualized, two extralaryngeal branches of the recurrent laryngeal nerve are traced to the entrance to the larynx; in fig. 5 - the lower branch of the inferior thyroid artery was traced to the lower pole of the thyroid lobe and, taking into account the identified lower parathyroid gland, it was ligated distally; in fig. 6 - revision of the right thyro-thymic ligament revealed an unpaired thyroid artery, on which the lower parathyroid gland is located; in fig. 7 - extirpation of the thyroid lobe, ipsilateral central lymph node dissection was performed.

In FIG. 1-7 positions indicate the following: 1 - sternothyroid muscle (partially dissected); 2 - upper pole of the thyroid lobe; 3 - short muscle branches of the anterior branch of the superior thyroid artery; 4 - anterior edge of the upper pole of the thyroid lobe; 5 - avascular space between the posterior surface of the thyroid lobe and the lower constrictor of the pharynx; 6 - posterior surface of the upper pole of the thyroid lobe; 7 - lower constrictor of the pharynx; 8 - external branch of the superior laryngeal nerve; 9 - anterior branch of the superior thyroid artery (ligated); 10 - posterior branch of the superior thyroid artery; 11 - visceral sheet of the internal fascia of the neck at the upper aspect of the ligament of Berry; 12 - esophagus; 13 - upper parathyroid gland; 14 - lower thyroid artery; 15 - recurrent laryngeal nerve; 16 - extralaryngeal laryngeal branches of the recurrent laryngeal nerve 17 - lower branch of the inferior thyroid artery; 18 - lower pole of the thyroid lobe; 19 - lower parathyroid gland; 20 - unpaired thyroid artery; 21 - central tissue of the neck; 22 - superior branch of the inferior thyroid artery. The method is carried out as follows.

A traditional access to the thyroid gland is performed by a Kocher incision with the release of the sternohyoid and sternothyroid muscles.

Initially, the upper pole of the thyroid lobe is mobilized. The sternothyroid muscle 1 is partially dissected closer to the thyroid cartilage. The traction of the upper pole of the 2nd lobe of the thyroid gland is performed laterally, which contributes to the tension of the short muscle branches of the 3rd anterior branch of the superior thyroid artery. The branches are ligated along the front edge 4 of the upper pole, thereby "opening" the avascular space 5 (Fig. 1). The latter is located between the posterior surface 6 of the upper pole of the thyroid lobe and the lower constrictor of the pharynx 7. In this space, 1-6 mm down and parallel to the line of attachment of the sternothyroid muscle 1 under the anterior branch of the superior thyroid artery, tissue dissection is performed in order to search for the external branch of the superior laryngeal nerve 8. After identifying the external branch of the superior laryngeal nerve, the anterior branch of the superior thyroid artery is isolated and selectively ligated 9 with preservation of the posterior branch 10 of the superior thyroid arteries (Fig. 2). Next, the traction of the upper pole to the medial side is performed and, along its posterior edge, the visceral sheet of the internal fascia of the neck 11 is opened at the upper aspect of the Berry ligament with precision preservation of the posterior branch 10 of the superior thyroid artery and its anastomoses with the branches of the inferior thyroid artery. An audit of this zone is carried out downwards to the esophagus 12 in order to detect the upper parathyroid glands 13 (Fig. 3).

At the next stage, the thyroid lobe is mobilized from the lateral side and dislocated into the wound, traction is performed anteriorly and medially. Tissue dissection is performed at the level of the lower third of the thyroid lobe in the region of the tracheoesophageal sulcus. The intersection of the inferior thyroid artery 14 with the recurrent laryngeal nerve 15 is visualized. The syntopy of the recurrent laryngeal nerve with the inferior thyroid artery is determined. The nerve is further traced all the way to the point of confluence with the larynx with visualization of all extralaryngeal laryngeal branches 16 (each traced to the point of its confluence) (Fig. 4). After that, tissues are dissected along the lower branch 17 of the inferior thyroid artery to the lower pole 18 of the thyroid lobe with a precise search for the lower parathyroid gland 19. When these structures are detected, the lower branch of the lower thyroid artery is ligated distally to the lower parathyroid gland located on it (Fig. 5).

A revision of the central fiber along the thyrothymic ligament is carried out on the same side in order to search for the lower 19 or additional parathyroid glands and their arteries (mediastinal branches of the inferior thyroid artery or unpaired thyroid artery 20). Taking into account these structures, the lower pole 18 of the thyroid lobe is separated from the central tissue of the neck 21, the lower venous vessels are ligated (Fig.6).

At the next stage, the isthmus is crossed and the thyroid lobe is mobilized from the medial side along the trachea to the tubercle of Zuckerkandl. Traction of the lobe is carried out in the lateral direction, which reduces the impact on the recurrent laryngeal nerve. The prelaryngeal tissue is excised with Dolphin's lymph nodes and the pyramidal lobe as a single conglomerate.

After the medial mobilization of the thyroid lobe, the traction is changed again and the dissection continues from the lateral side. The course of the upper branch 22 of the inferior thyroid artery to the tubercle of Zuckerkandl is traced with visualization of the superior parathyroid gland 13. The final extirpation of the thyroid lobe is performed with ligation distal to the superior parathyroid gland of the superior branch of the inferior thyroid artery while maintaining the anastomosis with the superior thyroid artery. Taking into account all visualized structures, an ipsilateral central cervical lymph node dissection is performed (Fig. 7).

The same actions are repeated from the contralateral side.

When the tumor is located in one of the thyroid lobes, preferably the operation begins with the affected lobe. In the presence of tumors in both lobes, as a rule, the lobe with the largest tumor is removed first.

Example

Patient T., 52 years old, was admitted to the hospital with a diagnosis of thyroid cancer, papillary variant T1bN1aMo (stage I).

Under anesthesia, traditional access to the thyroid gland was performed. The operation began with the allocation of the upper pole of the left lobe affected by the tumor process. The sternothyroid muscle was isolated at the upper pole of the thyroid lobe, partially crossed closer to the thyroid cartilage. Produced traction pole in the lateral side. Ligated short muscle branches of the anterior branch of the superior thyroid artery. The space behind the upper pole of the lobe was opened. The cricothyroid muscle was completely separated from the posterior surface of the lobe, and the inferior constrictor of the pharynx was visualized. An external branch of the superior laryngeal nerve was found on this muscle, running parallel to the line of attachment of the sternothyroid muscle. Ligation of the anterior branch of the superior thyroid artery was performed. Further, without crossing the vascular structures behind the thyroid lobe, the visceral sheet of the internal fascia of the neck was opened, the upper parathyroid gland, intimately adjacent to the thyroid lobe, was visualized. The parathyroid gland was carefully separated with preservation of the vascular structures belonging to the superior thyroid artery.

The venous vessels were ligated along the lateral surface of the thyroid lobe. The lobe is dislocated, retracted to the medial side and anteriorly. Behind the lower third of the lobe, a decussation of the recurrent laryngeal nerve and the trunk of the inferior thyroid artery was revealed. The nerve is traced downwards (goes in one trunk) and upwards to the "entrance" into the larynx (forms two branches at the level of the decussation). Next, the lower branch of the inferior thyroid artery was traced to the lower pole of the thyroid lobe, in which the lower parathyroid gland was identified. A branch of this artery is ligated over the lower parathyroid gland.

The revision of the ipsilateral central tissue of the necks revealed a supernumerary parathyroid gland located on a branch of the unpaired thyroid artery. The central tissue of the neck was separated from the lower pole of the thyroid lobe with the preservation of the supernumerary parathyroid gland and its blood supply vessel.

The next step was to cross the isthmus closer to the healthy lobe of the thyroid gland. The traction of the isolated lobe was changed to lateral, and mobilization was continued from the medial side up to the tubercle of Zuckerkandl.

The final extirpation of the left lobe was performed from the lateral side under visual control of the anterior branch of the recurrent laryngeal nerve, taking into account the course of the superior branch of the inferior thyroid artery and the location of the superior parathyroid gland. In the paratracheal tissue, there were 5 enlarged dense black lymph nodes up to 1 cm in diameter. Under visual control of the distal segment of the recurrent laryngeal nerve, branches of the inferior and unpaired thyroid arteries, inferior and additional parathyroid glands, unilateral central lymph node dissection was performed.

The same steps are performed on the right side. At the same time, the external branch of the right upper laryngeal nerve was identified in a typical location. The superior parathyroid gland was located near the esophagus on the posterior branch of the superior thyroid artery. The recurrent laryngeal nerve in the region of the intersection formed 3 branches, two of which "encircled" the tubercle of Zuckerkandl on both sides. The inferior parathyroid gland was located low on the trunk of the inferior thyroid artery.

No supernumerary parathyroid glands were found. By the end of the operation, all parathyroid glands were without color change (no signs of hypoxia). The operation was completed by layer-by-layer suturing of the wound, leaving rubber graduates.

On the 2nd day, no clinical signs of laryngeal paresis, hypoparathyroidism were detected in the patient. Laboratory tests: total blood calcium -2.42 mmol / l (2.2-2.6), parathyroid hormone - 4.8 pmol / l (1.3-6.9). An ultrasound of the vocal folds was performed: no signs of paresis and dyskinesia of the larynx were noted. The patient was discharged from the hospital on the 3rd day in a satisfactory condition.

The proposed method operated on 44 patients diagnosed with thyroid cancer with metastases in the central tissue of the neck. In the blood serum of all patients before surgery, the level of 25(OH)D, total calcium, albumin, parathormone was determined, ultrasound of the vocal folds was performed, consulted by an otolaryngologist. In 37 (84%) patients, vitamin D deficiency or insufficiency was noted (no preoperative treatment was performed). In 8 (18%) cases, secondary hyperparathyroidism was detected. Hypocalcemia at the preoperative stage was not noted in any case. In all patients, on days 2, 3, 7, 1, 6 months after the operation, the level of total calcium, albumin, and parathyroid hormone in the blood serum was determined, ultrasound of the vocal folds was performed on the 2nd day after the operation and, if necessary, were consulted by an otolaryngologist. In the postoperative period, 10 (23%) patients had hypocalcemia (corrected calcium less than 2.1 mmol/l). In 5 (11%) of them, a decrease in parathyroid hormone below the reference value was detected and clinical manifestations of hypoparathyroidism were noted. However, the symptoms were not pronounced (only paresthesia without convulsive syndrome) and appeared 48-72 hours after surgery (the level of calcium in the blood decreased gradually). These patients were prescribed calcium and vitamin D preparations, and the duration of administration was 1-4 weeks. Intravenous calcium preparations were not used. In the late postoperative period (6 months or more), permanent hypoparathyroidism was not recorded in any of the patients. In 1 (2%) patient, left-sided paresis of the larynx was detected, which resolved spontaneously after 1 month.

The proposed method improves the results of surgical treatment of patients diagnosed with thyroid cancer with metastases in the central tissue of the neck. While maintaining the radical nature of the operation, the risk of postoperative complications decreases. Thanks to this, it is possible to improve the quality of life of this category of patients, to get rid of the constant intake of calcium and vitamin D supplements, and to prevent severe chronic diseases in the late postoperative period.

Claims (1)

A method for surgical treatment of thyroid cancer with metastases to the lymph nodes of the central tissue of the neck, including access, isolation of the superior thyroid artery, mobilization of the thyroid gland lobes from the lateral side and dislocation of them into the wound medially and anteriorly, visualization of the recurrent laryngeal nerves and tracing them to the place where they flow into the larynx, isolating the inferior thyroid arteries at the intersection with the recurrent laryngeal nerves and tracing the arteries and their branches to the thyroid capsule glands, visualization of the parathyroid glands in these areas, ligation of the branches of the lower thyroid arteries, thyroidectomy, removal of the central fatty tissue of the neck with lymph nodes, characterized in that after access is made, the sternothyroid muscle is dissected sequentially first from one side and then from the contralateral side in the area of attachment to the thyroid cartilage, the muscle branches of the anterior branch of the superior thyroid artery are ligated, then the upper pole of the lobe of the thyroid gland is separated from the lower constrictor of the pharynx and in this space below the line of attachment of the sternothyroid muscle to the thyroid cartilage, the external branch of the superior laryngeal nerve is identified, after which the anterior branch of the superior thyroid artery is selectively ligated; the visceral sheet of the internal fascia of the neck is opened at the upper aspect of the Berry's ligament with precision preservation of the posterior branches of the superior thyroid artery and its anastomoses with the branches of the inferior thyroid artery, at the same time, this zone is inspected posteriorly to the esophagus to detect the upper parathyroid glands; after ligation of the lower branch of the inferior thyroid artery, the isthmus of the thyroid gland is crossed, and then alternately from the lateral, and then from the medial side, they approach the tubercle of Zuckerkandl, forming the vascular pedicle of the thyroid gland, with precise isolation and preservation of the anterior extralaryngeal branch of the recurrent laryngeal nerve, the thyroid lobe is extirpated; after that, the central tissue of the neck is revised to the thymus with visualization of the mediastinal branches of the inferior thyroid artery or branches of the unpaired thyroid artery, and if parathyroid glands are detected, ipsilateral central lymph node dissection is performed while preserving the parathyroid glands and their vessels; after that, the entire sequence of actions is carried out from the contralateral side.