RECURRENT LARYNGEAL NERVE AND PARATHYROID GLAND SAVING BY SPRAYING METHYLENE BLUE DURING THYROIDECTOMY

Hany Mohamed, Ashraf Goda and Hatem Mohammed. General Surgery Departments, Faculty of Medecine, Zagazig University. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 11 December 2018 Final Accepted: 13 January 2019 Published: February 2019

The major concerns in thyroid operations are exposure and protection of RLN .Staining of the nerve fiber by the methylene blue (MB) is old procedure 5 , It was used to visualize the branches of the vagus nerve 6 facial nerve trunk 7 , stumps of the nerves 8 and fibres of autonomic nerves 9 in many surgeries . The procedure of surgery represent the main factor alters the results of the operation 10 .
Vocal cords Paralysis may cause serious complications in phonation, respiration and psychological disturbances which affect the patient's life style 11 .
Basically, the important step to protect the PGs and prevent its hypofunction is good identification. However,the very small size of the PGs that located in the paratracheal fatty Tissues which have a color like to the PGs. It is not easy to identify the all PGs by the naked eye during operation even by the experienced surgeons 12,13 . Formerly, many surgeons didn't dissect near to RLN to avoid its injury. Now a days, the endocrine surgeons reported that is not accepted. The visualization and protection of RLN are very important to prevent its injury 14 .In our present study, we aimed to evaluate the using MB spraying technique for safe identification of RLN and PGs during total thyroidectomy.

Patient and methods:-
Our prospective study was approved by Research Ethics Committee of Zagazig University hospital and was done in general surgery department from March 2017 to September 2018 and follow up for about 6 months, included (53) cases with benign and malignant thyroid swelling operated by total thyroidectomy. Patients with recurrent thyroid surgery, preoperative vocal cords paresis, or retrosternal goiter were excluded. The patients underwent complete history taking, clinical examination, laboratory investigations including TSH,freeT3,T4, serum calcium level, neck US, C.T neck in some cases and indirect laryngoscopy pre and post operatively to assess the vocal cords mobility pre-and postoperatively. Informed consent was taken from all cases.
Operations were done under general anesthesia, neck Kocher collar incision followed by strap muscles separation in midline, ligation of middle thyroid veins, thyroid lobe dissection, ligation of superior thyroid artery then cutting within the upper pole of thyroid. When we reach area where the RLN was suspected to enter the tracheooesophageal groove and the parathyroid gland can't be identified, the thyroid lobe retracted medially ( fig. 1) and 0.5 ml of MB was sprayed on the retracted lobe and the surrounded tissues including the PGs, inferior thyroid artery, veins, RLN and surrounding muscles , fatty tissues. The arteries and RLN were not stained and still relatively white ( fig. 2). PGs had washed out the stain within three minutes and return to their original yellow color, after identification of the RLN and PG washing by saline to clear the field from the stain to make the dissection easier, wash-out time of thyroid gland not less than 15 minutes and 25 minutes for surrounding structures. The thyroid dissected from the trachea and operation is completed by anatomical closure with drain.

Follow up:
All patients were followed up postoperatively by serum calcium, wound complications and laryngoscopy before discharge then in outpatient clinic weekly for one month then monthly for six months.

Results:-
This study was conducted on (53) patients operated by total thyroidectomy, 43 females (81.1%) and 10 males (18.9%); age ranged from 27 to 61 years (mean: 41.5 year), the patients had different thyroid diseases; 35(66.04%) simple nodular goitres, 9(16.98%) solitary thyroid adenoma, 5(9.43%) cancer thyroid and 4(7.55%) Graves' disease. The mean of cases discharge was 1.6 days (1-4 days), no cases of wound seroma, infection dehiscence or other complications. No cases of operative mortality. Only 4 cases (7.55%) suffered from transient hypocalcaemia, for a maximum of four days (calcium level <8 mg/dL. and clinical picture of hypocalcaemia) which improved by oral calcium and vitamin D supply. In our study the RLN can be visualized in 47 cases (88.7%) after spraying the MB In firstly but in the remaining six cases (11.3%) the RLN was present in deeper level and need more dissection until it is detected and saved. No cases were encountered of vocal cord paralysis or hypoparathyroidism.  25 . The rate of hypocalcemia reported post thyroidectomy ranged between 1% to more than 50% 26,27 . Although most cases of post thyroidectomy hypocalcemia are transient, the rate of permanent hypoparathyroidism is unusual and must be less than 1% 28 . In our study, Only 4 cases (7.54%) suffered from transient hypocalcaemia, four days maximally which treated by oral calcium supply and normal parathyroid hormone, this result agree with the results of previous studies.
We noted that the time needed for wash-out of the PGs (3 minute) was less than that of the thyroid (15 minute) .This may be due to the differences in the lympho-vascular tissues. The lympho-vascular tissue of PGs is highly dense. This quality is vital for rapid wash out of MB staining. Unstaining of RLN in the procedure is due to the nerve has a schwann sheath covering and avascular structure 29 .
The unstaining of the artery is due to the thickness of wall and reverse blood flow (from the heart to the gland not from the gland to the heart) and. As the veins carry methylene dye from the gland, they rapidly changed into blue color. There were no complications reported from MB spraying in our study ensuring the safety of using MB staining 29 .
Traditionally, we preserve RLN through detection of its relation to the inferior thyroid artery, ligament of Berry and trachea-esophageal groove, as a land-marks. But, due to presence of many variations in the neurovascular relationship and different thyroid diseases, detection of the artery not confirm accurate identification and protection of RLN 29 .
So by spraying MB over the perithyroidal tissues, the surgeon can detect and visualize RLN, PGs and the inferior thyroid artery. when they be visualized, the nerve and its branches is followed up safely along the whole course up to the larynx. After identification of the PGs, great care is considered to protect their blood supply 29 .in our study no cases of wound complication or operative mortality.

Conclusion:-
Intraoperative spraying of the Methylene blue is good, simple and safe technique during thyroidectomy which enables the surgeon to visualize and protect both the RLN and PGs from potential complications. Thus safe the patients from troublesome complications which may affect their life style.