In recent years, due to the increasing incidence of thyroid cancer, total thyroidectomy and lymph node dissection in the central region have gradually increased, and in this type of surgery, laryngeal recurrent nerve injury and parathyroid hypoplasia are the most important and threatening complications for patients. In order to avoid these complications, Professor Wang Shilin of the General Surgery Department of the Air Force General Hospital has adopted a [two-pronged] approach since 2013, namely intraoperative recurrent laryngeal nerve monitoring and nano-carbon lymphography (negative parathyroid imaging), which has effectively prevented the above complications and achieved better results.
I. Recurrent laryngeal nerve injury
Injury to the recurrent laryngeal nerve (RLN) is one of the serious complications of thyroid surgery, and unilateral injury to the RLN causes vocal cord paralysis and hoarseness. In contrast, bilateral laryngeal nerve injury, resulting in vocal atresia, requires the patient to undergo a tracheotomy and be intubated with a tracheal tube for life. The literature reports that the incidence of permanent vocal cord paralysis is 1-2% and temporary is 5-6%. It accounts for 50% of medical disputes in thyroid surgery.
The application of intra-operative neuromonitoring (IONM) in thyroid surgery has undergone a process of development, initial clinical application, controversy, continuous research and refinement, until it was basically affirmed. The monitoring instruments currently used have evolved from the first generation to the third generation of monitors. The operation technique has been gradually standardized from the original non-standardized and non-uniform, and even more improved after the publication of the operation guideline (four-step method) by the International RLN Intraoperative Monitoring Organization in 2010.
Figure 1, third generation neuromonitoring
Intraoperative neuromonitoring requires the use of a special tracheal cannula with a special electrode piece attached to it and various wires connected one-to-one to a special terminal block and connected to the monitor. When the probe electrode on the operating table probes the laryngeal nerve or the adjacent laryngeal nerve, the instrument will sound a “beep” to remind the surgeon that the laryngeal nerve is nearby.
Figure 2, laryngeal nerve not found during surgery
In the recent experience of Chan et al. 1000 cases, independent risk factors for laryngeal recurrent nerve injury were malignant thyroid tumor and secondary surgery. Without the use of intraoperative nerve monitoring, the rate of nerve injury in high- and low-risk patients was 19% vs. 4.5% (P=0.019). For those who used intraoperative nerve monitoring, the rate of nerve injury in high- and low-risk patients was 7.8% vs. 3.8% (P>0.05).
Indications for retrograde laryngeal nerve monitoring: thyroid masses located dorsal to the gland, suspected recent intracapsular hemorrhage or nail cancer; hyperthyroidism with a large gland with abundant blood flow; nail cancer requiring cervical clearance, especially in the central region; reoperation of the thyroid gland; retrosternal or giant goiter with consideration of displacement of the retrograde nerve; suspected laryngeal non-retrograde nerve (visceral transposition, subclavian artery variation); pre-existing unilateral vocal cord paralysis requiring surgery on the contralateral side. Those with total thyroidectomy, especially lumpectomy; repair of the recurrent nerve; parathyroid surgery; professions related to vocalization, such as actors, teachers, etc.
II. Nanocarbon lymphography
Nanocarbon suspension injection (Canaline) is a suspension supported by nanocarbon particles with a diameter of 150nm, which has a high lymphatic tendency and is the only approved lymph node tracer on the market in China. Since the capillary endothelial cell gap is 20-50nm and the capillary lymphatic endothelial cell gap is 120-500nm, the nanocarbon injected into the thyroid tissue does not enter the blood vessels, but rapidly enters the capillary lymphatic vessels or is phagocytosed by macrophages and stays and accumulates in the lymph nodes, causing the lymph nodes to be black-stained. The specific method of intraoperative nanocarbon lymphatic imaging is: after revealing the thyroid gland, 0.2-0.25 ml of nanocarbon is injected in 2-3 points around the tumor, or the upper and lower poles of the thyroid gland. Unilateral lesions are injected unilaterally, and bilateral lesions, if the contralateral side is obvious, add contralateral injection, and the dosage is the same as unilateral.
Figure 3. Nanocarbon suspension injection (Canaline)
Significance of nano-carbon lymphatic imaging.
(1) Black staining of lymph nodes and no staining of parathyroid glands, which helps to identify lymph nodes and parathyroid glands and avoid parathyroid misincision.
(2) Black staining of regional lymph nodes to ensure the thoroughness of lymph node dissection.
(3) Improve the detection rate of lymph nodes, especially those <5 mm, to provide a basis for postoperative tumor staging and other treatments.
(4) It helps to identify cancerous lesions because the normal thyroid gland stains after nanocarbon injection, but thyroid cancer does not stain.
III. Clinical study results of general surgery department of Air Force General Hospital
In order to avoid these complications, Dr. Wang Shilin, chief of the general surgery department of the Air Force General Hospital, used intraoperative laryngeal recurrent nerve monitoring and/or nanocarbon lymphatic imaging in 176 patients with thyroid cancer in the past 2 years. The whole group had 138 cases of nerve monitoring and 36 cases did not have nerve monitoring. The nano charcoal lymphatic imaging was performed in 164 cases, and the nano charcoal lymphatic imaging was not performed in 12 cases. Intraoperative neuromonitoring and nano charcoal lymphography were performed in 124 cases.
Total thyroidectomy with lymph node dissection in the central region was performed in 113 cases, and near-total resection with unilateral lymph node dissection in the central region was performed in 7 cases. There were 34 cases of total thyroidectomy with isthmus resection and unilateral central lymph node dissection. There were 20 cases of total thyroid excision and lateral cervical lymph node dissection, including 17 cases of total thyroid excision, 1 case of residual gland excision, and 2 cases of simple cervical dissection. Partial thyroidectomy was performed in 1 case. One case of metastatic thyroid cancer was resected.
Papillary carcinoma was the most frequent pathological type, with 175 cases, and follicular carcinoma was only 1 case. There were 79 cases of micro papillary carcinoma and 31 cases of lymph node metastasis (39.24%). There were 50 cases of multifocal carcinoma (including 17 cases of bilateral carcinoma) and 16 cases of lymph node metastasis (32%). Of 145 cases of lymph node dissection in the central area, 60 cases were positive (41.37%)
Nerve monitoring was performed in 138 cases, and unilateral or bilateral monitoring was selected according to the surgical style, and laryngeal return or/and vagus nerve monitoring was performed. There was no intraoperative nerve injury.
Blood calcium was checked 24 hours postoperatively in 100 cases, and was low in 33 cases, with values of 1.5-1.9 (2-3). 99 cases had blood phosphorus checked postoperatively, and was high in 13 cases, 1.7-2.2 (0.5-1.6). 92 cases had whole segment parathyroid hormone checked, and was low in 21 cases, 0.533-1.23 (1.48-7.63). In 12 cases, intraoperative parathyroid transplantation was performed. 9 cases had postoperative blood calcium and phosphorus, 5 of which had lower than normal blood calcium and 2 had increased blood phosphorus. 8 cases had whole-segment parathyroid hormone tests, 4 had normal whole-segment parathyroid glands and 4 had low blood calcium. During the follow-up period of 6-12 months, no one case of severe hypocalcemia occurred.
IV. Summary.
1. Thyroid cancer surgery is a relatively complex, precise and meticulous major neck surgery. Once complications occur, they are serious and last much longer than those of general gastrointestinal surgery, so they should be taken seriously.
Intraoperative laryngeal nerve monitoring and nano-carbon lymphography can effectively reduce the damage to the laryngeal nerve and parathyroid glands, ensure the thoroughness of lymph node dissection and improve the detection rate of lymph nodes, which is of positive significance for postoperative staging of thyroid cancer and guiding the subsequent treatment.
3. At present, intraoperative laryngeal nerve monitoring and nano-carbon lymphography for thyroid cancer surgery are not covered by medical insurance. With the increasing incidence of thyroid cancer and surgery, they should be taken seriously by relevant functional departments. Under the existing circumstances, patients and their families can generally accept the necessity of nerve monitoring and nano-carbon lymphatic imaging if they are explained to them.