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Video-assisted parathyroidectomy

Authors

Abstract

The description of the video-assisted parathyroidectomy covers all aspects of the surgical procedure used for the management of primary hyperparathyroidism.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: incision, dissection, exploration.
Consequently, this operating technique is well standardized for the management of this condition.

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Publication

2003-05

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E-publication

WeBSurg.com, May 2003;3(05).
URL: http://www.websurg.com/doi-ot02en241.htm

Video-assisted parathyroidectomy

1. Introduction

Improved preoperative imaging techniques (high-resolution ultrasonography and sestamibi scan) and an intraoperative assay to confirm normalization of parathyroid hormone (PTH) have allowed changes in the treatment of primary hyperparathyroidism.
Today, more surgeons are comfortable with unilateral exploration, which allows for smaller incisions, shorter operative times and the use of sedation instead of general anesthesia in some instances. Laparoscopic procedures were initially limited to body areas with pre-existing cavities; access to potential spaces has extended the spectrum of minimally invasive endoscopic surgery.
Since the first report of an endoscopic parathyroidectomy in 1996 (Gagner), video-assisted techniques have been applied to surgery of the neck, and several series have documented the feasibility of these approaches for parathyroid and thyroid disease.
Minimally invasive video-assisted parathyroidectomy (MIVAP) was first described in 1997 (Miccoli et al.). It is characterized by an external retraction rather than by gas insufflation which, with time, has been completely eliminated as the operative space is created solely through blunt dissection. The access is unique at the level of the central neck and this helps a complete bilateral exploration of the parathyroid glands in case preoperative imaging studies are not conclusive in locating the parathyroid adenoma.

2. Anatomy

• Embryology

• Development 1

The parathyroid glands derive from the endoderm and the adjacent mesenchyma. The inferior parathyroid glands derive from the third pharyngeal pouch, prior to the appearance of the thymic rudiment. Although the connection between the pouch and the pharynx is soon lost, the connection between the thymic and parathyroid rudiments persists for some time, and the latter passes caudally to the developing thymus.
1. First pharyngeal pouch
2. Second pharyngeal pouch
3. Third pharyngeal pouch
4. Fourth pharyngeal pouch
5. Lung bud
6. Esophagus
7. Ultimobranchial body
8. Superior parathyroid gland
9. Thyroid gland

• Development 2

The superior parathyroid glands develop in a similar manner from the dorsal recess of the fourth pharyngeal pouch. They come into relation with, and appear anchored by the lateral lobes of the thyroid gland and thus remain cranial to the parathyroid gland derived from the third pharyngeal pouch.
1. First pharyngeal pouch
2. Second pharyngeal pouch
3. Third pharyngeal pouch
4. Fourth pharyngeal pouch
5. Thymus
6. Inferior parathyroid gland
7. Ultimobranchial body
8. Superior parathyroid gland
9. Thyroid gland

• Generalities

1. Superior parathyroid glands
2. Inferior parathyroid glands
Most individuals have four parathyroids situated on the posterolateral capsule of the thyroid gland. But the number may vary from two to six. More than four parathyroid glands may be found in 5% of cases.
Characteristically the glands are yellowish-red or yellowish-brown. Minute blood vessels in the pedicle of the gland may help differentiate them from other tissues. The parathyroid glands vary greatly in size, shape, number, and location.

• Parathyroid glands

• Lower

1. Posterior aspect of inferior pole of thyroid gland
2. Lateral aspect
3. Anterior aspect
4. Thyrothymic ligaments
In 61% of cases, the lower parathyroid glands are situated at the level of the inferior poles of the thyroid gland, on its posterior, lateral or anterior aspects. In 26% of cases, they are situated in the thyrothymic ligaments or on the upper cervical portion of the thymus. More rarely, they are situated at the level of the middle third of the posterior aspect of the thyroid gland (Ackerstrom et al., 1984).

• Upper

The upper parathyroid glands are generally located on the posterior aspect of the middle third of the thyroid lobes, approximately 1 cm above the crossing of the inferior thyroid artery and the recurrent nerve. Often, when the parathyroids are difficult to find, it is helpful to trace the course of the inferior thyroid artery and its branches.

• High and low ectopias

1. High ectopias
2. Low ectopias
Anomalies of migration of the parathymus are responsible for high or low ectopias of the lower parathyroid glands. High ectopias along the carotid sheath from the angle of the mandible to the lower pole of the thyroid gland do not exceed 2% (Ackerstrom et al., 1984). Low ectopias, found in 3.9% to 5% of cases, derive from delayed separation of the parathyroids from the thymus. Inferior parathyroids may thus be located in the anterior mediastinum, usually in the thymus.

• Vasculature

1. Superior thyroid artery
2. Inferior thyroid artery
3. Thyrocervical trunk
About 80% to 86% of the blood supplying the superior parathyroid glands and 90% to 95% of the blood supplying the lower parathyroid glands originates from the inferior thyroid artery. However, superior thyroid arteries contribute significantly to the parathyroid blood supply. Sufficient parathyroid blood supply is ensured by collaterals between thyroid vessels and neighboring esophageal and tracheal arteries.

3. Indications

Indications
All patients with sporadic primary hyperparathyroidism are potential candidates for MIVAP. Patients with a small, well-localized adenoma, but without concomitant thyroid disease or previous neck surgery are most suitable. For the minimally invasive techniques, it is mandatory to follow the eligibility criteria, which are:
- no previous neck surgery;
- absence of goiter;
- clear preoperative localization of a single adenoma;
- no suspicion of multiglandular disease or hyperplasia.

Nevertheless, when the surgical team is confident with this approach, most classical contraindications may be interpreted more flexibly in order to distinguish between relative and absolute contraindications. Small thyroid nodules may be surgically treated during the same procedure as long as they do not exceed 3 cm in diameter. As quick bilateral exploration is feasible through the same access, patients without preoperative localization could undergo MIVAP. A lateral approach can be useful in case of previous neck surgery, as well as in the open procedure.

Contraindications for MIVAP
Absolute contraindications: previous neck surgery; large goiter, parathyroid carcinoma
Relative contraindications: previous neck irradiation; large adenoma (>3 cm); lack of preoperative localization; multiple endocrine neoplasia or suspicion of multiglandular disease.

4. Preop period

An extensive preoperative biological evaluation is necessary to confirm the diagnosis of primary hyperparathyroidism.
Once the diagnosis is established, a correct preoperative localization of the lesion is generally considered mandatory before performing MIVAP or any other minimally invasive approach to primary hyperparathyroidism. Localization can be based either on an ultrasound examination or on a double phase 99m Tc-labeled sestamibi scan. In many cases, both imaging studies have already been performed before the patient being referred to the surgeon. We prefer an ultrasound examination using a linear transducer (8-13 mHz) with color Doppler capability. In our experience, ultrasound has two important advantages over scintigraphy. It is much more accurate in revealing anatomical details, in defining the size and position of the adenoma and its relationships with vascular structures. The sensitivity of ultrasonography is comparable to scintigraphy. Lesions over 3 cm in diameter must be carefully evaluated. Large adenomas are sometimes difficult to remove endoscopically.

5. Operating room set-up

• Patient

- supine position without neck hyperextension;
- conventional neck preparation and draping;
- a sterile drape covering the skin.

• Team

1. The surgeon is on the right side of the table.
2. The first assistant is on the side of the table opposite the surgeon.
3. The second assistant is at the head of the table.
4. The scrub nurse is on the left side of the first assistant.

• Equipment

1. Double-screen
2. Ultrasound generator
3. Material for PTH dosage

6. Instrumentation

1. Forward-oblique telescope 30°, diameter 5 mm, length 30 cm
2. Suction dissector with cut-off hole and stylet, blunt, length 21 cm
3. Ear forceps, very fine, serrated, working length 12.5 cm
4. Conventional tissue retractor
5. Tissue retractor, double-ended, length 12 cm
6. Clip applier for vascular clips (5 mm)
- straight scissors, length 12.5 cm;
- vessels suspender hook, malleable, length 21 cm;
- elevator, 2 mm wide, blunt, length 19 cm;
- ultrasonic scalpel.

7. Incision

• Skin incision

A 15 mm horizontal incision is performed 2 cm above the sternal notch.
The midline opening is a critical point as it should be incised on a bloodless plane; any minimal bleeding at this point prevents the surgeon from carrying on with the procedure.
The surgeon should use the electrocautery with its blade protected with a thin film of sterile drape.

• Variation

In case of repeat surgery, a lateral access instead of the standard midline access is possible. This avoids entering fibrous tissue where recognition of anatomical planes and structures such as the recurrent nerve may be difficult. The incision is made just medially to the sternocleidomastoid muscle and the same blunt dissection is performed until the thyroid space is well-exposed.

8. Dissection

• Preparation

Subcutaneous fat and platysma are carefully dissected to avoid bleeding. The cervical linea alba is divided longitudinally as much as possible (3-4 cm). The strap muscles on the affected side are then gently retracted with one small retractor; a second retractor is placed directly on the thyroid lobe, which is retracted medially and lifted up. The dissection of the lobe from the strap muscles is completely achieved through the skin incision by gentle retraction, using conventional instruments.
The two small retractors maintain the operative space. A 30° 5 mm endoscope is inserted through the skin incision. Under endoscopic vision, the dissection of the thyrotracheal groove is completed with small 2 mm instruments: atraumatic spatulas in different shapes, spatula-shaped aspirator, ear-nose-throat forceps and scissors.

• Tip

1. Spatula-shaped aspirator
Washing and cleaning the operative field is simple because there are no trocars. Water can be injected directly with a syringe; its aspiration is facilitated by the use of the spatula-shaped aspirator. The procedure can be continued through the spatula; smoke and liquids can be aspirated without introducing extra instruments into the incision.

• Ligature/middle vein

1. Middle thyroid vein
2. Adenoma
The first vessel to be ligated is the middle thyroid vein, when present, or the small veins between the jugular vein and the thyroid capsule. Hemostasis is achieved by means of small 3 mm conventional vascular clips or by ultrasonic scissors.
This step helps to prepare the thyrotracheal groove where the recurrent nerve will be searched for later on.

9. Exploration

• Exploration

1. Adenoma
Exploration starts from the side where the adenoma was located on preoperative imaging studies, but bilateral exploration can be achieved from the central incision.
Blunt dissection by small atraumatic spatulas helps visualize the recurrent laryngeal nerve and the adenoma.
Tip: once the surgeon has identified the supposed parathyroid adenoma, a sudden change of color during handling generally serves to confirm this.
As soon as the lesion is seen, the first sample is obtained (visualization sample). During the dissection of the adenoma, a second sample is obtained (manipulation sample).
Tip: quick intraoperative parathormone assay evidences that any hyperfunctioning tissue has been removed; in case it fails to decrease, a bilateral exploration is possible with this technique because it takes advantage from a central access which helps proceed to the opposite side with no additional scars. A second adenoma or even a hyperplasia can be treated in the same way.

• Dissection of adenoma

1. Recurrent laryngeal nerve
2. Pedicle
3. Adenoma
While dissecting the adenoma, it is mandatory to have the laryngeal nerve under direct vision to avoid injury when the hilus is ligated.
An excellent anatomical landmark for searching for the recurrent nerve is the posterior lobe of the thyroid (also known as the tubercle of Zuckerkandl) because it generally lies over the nerve. In conventional surgery, the recurrent nerve is generally identified at its emergence from the thoracic outlet, but this area may be difficult to visualize with the endoscope whereas the middle part of the thyroid gland is highly visible and nerve dissection can be carried out efficiently.
Danger: the use of electrocautery should be very limited because energy transmission in such a small space can jeopardize the recurrent nerve. If its use is necessary, a correct previous identification of the nerve is mandatory.
Variation: if the parathyroid adenoma is located deep in the anterior mediastinum, the endoscope is best moved from its usual location on the left hand of the assistant and put uppermost on the left hand of the operator to allow better exposure of the thymus tail where the adenoma can sometimes be found.

• Surgical resection

1. Pedicle
The pedicle of the adenoma is identified and isolated. It is then cut by means of small scissors between small vascular clips.
Danger: the integrity of the parathyroid capsule must be assured throughout the procedure and also during the extraction because its effraction may result in the spreading of parathyroid cells. This is very dangerous as cell implantation is possible and may cause recurrent disease or even parathyreomatosis.
Quick intraoperative intact parathyroid hormone assay (qPTH) is utilized during the procedure. The completeness of the surgical resection of all hyperfunctioning parathyroid tissue is confirmed by a decrease of more than 50% in qPTH values compared to the highest pre-excision level. Measurements are obtained when anesthesia is induced, when the adenoma is visualized and 5 and 10 minutes after the adenoma is removed.

• Conversion

Conversion rate can be estimated to be around 8.8% (Miccoli et al., 2000). The reasons for conversion can be represented by: parathyroid carcinoma or difficult dissection, but, much more often, by the ectopic position of the gland either in the neck or in the mediastinum. It must be stressed though that in some cases, even after conversion the adenoma was not found.

10. Postop period

The most common complication after parathyroidectomy is the hypocalcemia subsequent to damage to the remaining parathyroid glands; however, it is rare, particularly after a minimally invasive procedure such as the one proposed in this chapter (Lorenz et al., 2000).
In the past, this complication was mainly due to the extensive dissection of all 4 parathyroid glands and to their possible biopsy; at present all the less invasive operations performed, starting also with unilateral exploration, have sharply decreased this complication. When it occurs it is only transient and can be easily managed with simple calcium medication for 2 or 3 days following surgery.
In contrast, when the surgeon has not achieved the goal of the operation, ie the ablation of all the hyperfunctioning tissue, calcium levels will remain high in the first days after surgery. For the abovementioned reasons calcium serum measurement should be obtained immediately on the first postoperative day. In case a persistent hyperparathyroidism occurs, an accurate workup of the patient is necessary to search for the possible hyperfunctioning parathyroid gland left behind by the surgeon. Persistent hyperparathyroidism can be due either to a hyperplasia or a second adenoma missed out during the operation. A different surgical failure is represented by recurrent hyperparathyroidism, which is mainly due to a metachronous hyperplasia of 1 or more glands: it can sometimes be part of a more complex multi-endocrine syndrome (MEN 1 and MEN 2). A new and even more accurate workup is mandatory and genetic analysis should be added to the imaging studies.
Even rarer is vocal cord palsy due to damage to the recurrent laryngeal nerve: its incidence is more or less the same as in open surgery (Udelsman, 2002). A laryngoscopy will be performed only in presence of a clear dysphonic voice; its routine use is unnecessary.

11. Conclusions

MIVAP is characterized by a unique central incision, which can offer 2 main advantages:
- the possibility of exploring both sides in case of controversial preoperative imaging;
- the possibility of operating on an associated thyroid lesion on the side opposite to the parathyroid lesion.
The results obtained by the most widely adopted endoscopic parathyroid procedures demonstrate that the complication rate is the same as in open surgery; in particular, recurrent nerve palsy is in all series below 1% (Henry et al., 2001), which is the same as in standard parathyroidectomy (Carty et al., 2002). Furthermore postoperative hypocalcemia proved to be even lower than in conventional surgery, according to some authors (Lorenz et al., 2000).
Even though it is still too early to draw conclusions about the recurrence rate, we can assume that the rate of persistent disease has not changed since the introduction of endoscopic parathyroidectomy (Miccoli, 2002). In the meantime at least 2 prospective studies exist showing that both postoperative cosmetic outcome and postoperative discomfort are significantly better with minimally invasive parathyroidectomy than with conventional neck bilateral exploration (Miccoli et al., 1999; Goldstein et al., 2000).

12. Reference

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