Year
Ref.
First MIVAT performed in Pisa
1998
First series reported in literature
1999
Miccoli et al.1
MIVAT and CT demonstrate similar surgical results
2001
Miccoli et al.2
MIVAT and CT demonstrate similar oncological results
2002
Miccoli et al.3
MIVAT and CT demonstrate a similar “manipulation” of the thyroid gland
2005
Lombardi et al.4
Central neck dissection is feasible with the MIVAT technique in selected cases
2007
Miccoli et al.5
MIVAT is demonstrated to be a safe and reproducible technique
2002, 2008
Miccoli et al.6; Terris et al.7
MIVAT and CT demonstrate similar oncological results after a 5-year follow-up
2009
Miccoli et al.8
While other complicated and often non-reproducible endoscopic techniques were abandoned, this operation has now become the most widespread technique for minimally invasive thyroidectomy. As a true minimally invasive approach, its popularity is partially attributable to the myriad advantages that it offers to patients over traditional thyroidectomy techniques. This procedure has been shown to result in less postoperative pain, faster recovery times, and greater patient satisfaction with their results while having a similar or better complication profile compared to conventional thyroidectomy. Further contributing to its attractiveness is MIVAT’s standardization and thus reproducibility. As will be described, MIVAT largely recreates the steps of conventional thyroidectomy, making it relatively easy to learn and master.
Selection Criteria
The extent of the operation does not represent a limit of the technique as the surgeon can strictly adhere to the basic rules of a conventional thyroidectomy. As a result, when necessary, a near-total or an extracapsular total thyroidectomy can be achieved, according to the oncologic principles of thyroid surgery. A level VI (central neck) lymph node dissection can also be performed with the MIVAT technique. However, this should be limited to cases of prophylactic neck dissections.
The possibility of performing a thorough total thyroidectomy with the MIVAT technique was demonstrated during the years that followed its introduction. Its safety and efficacy documented, the indications for MIVAT expanded from benign disease to the treatment of low- and intermediate-risk papillary and follicular carcinomas. Subsequently, it has been shown to be appropriate for the treatment of medullary carcinoma in patients with a RET mutation, requiring not only a total thyroidectomy, but also a prophylactic central neck dissection.
In order to have successful outcomes, the following are broad inclusion and exclusion criteria:
Benign thyroid nodules under 35 mm in their largest diameter or cytologically malignant (or suspicious) nodules under 20 mm, together with
A thyroid volume (ultrasonographically estimated) under 25 ml
No suspicion of metastatic lymph nodes in the central neck
No evidence of metastatic or suspicious lymph nodes in the lateral neck
No evidence of severe thyroiditis
As a suggestion, we always recommend to strictly adhere to the indications proposed, since every extension can cause unnecessary and undesired complications or conversions.
The Technique
The general principle behind the MIVAT technique is to perform a thorough thyroidectomy following the basic principles of the traditional thyroid surgery while gaining the advantages of endoscopic magnification. Critically, the endoscope is used only when it can improve the outcome of the procedure (thus the term “video-assisted” and not “endoscopic”).
Instruments
The instruments specifically dedicated to MIVAT are a 30°, 7 or 5 mm, 29 cm long endoscope, a 21 cm long suction dissector (used to avoid the fogging of the endoscope resulting from the steam produced by the energy instrument), two 2 mm elevators of approximately the same length as the suction dissector, small grasping forceps (15 cm long), scissors (8 mm blades, 8 cm long), and two small retractors (16 cm long). Other instruments often utilized are an energy device of choice, titanium clips, and conventional forceps used for thyroid surgery. An insulated Bovie tip should be used to avoid skin burns and inadvertent injury to surrounding structures (given the limited working space).
Positioning
The operation can be conducted under general (either with orotracheal intubation or laryngeal mask airway) or locoregional anesthesia, following the surgeon’s, anesthesiologist’s, and patient’s preferences.
The patient is placed in the supine position, with the neck only slightly hyperextended. Avoiding significant neck extension is one of the factors that explains the decreased pain associated with this procedure.
The primary surgeon will stand on the right side of the patient. Two assistants are employed. The camera assistant is positioned on the left side, across from the primary surgeon. The second assistant, who holds the retractors, stands at the head of the bed, facing the feet. The monitors are placed at both sides of the patient’s head. The main monitor is in front of the primary surgeon. The second monitor is helpful but optional.
The camera assistant will always hold the endoscope looking toward the patient’s head, positioned slightly away from the axis of the patient’s midline, depending on the working side. The angled endoscope should always be used in one of two main positions: looking upside-down (30° lens looking inferiorly) and downside-up (30° angle looking upward), with no intermediate positions. This standardization allows the surgeon to always obtain the same visualization of the anatomy and orientation toward the neck. This is particularly crucial for non-experienced surgeons during all steps of the procedure.
Procedure Details
For teaching purposes we divide a MIVAT lobectomy into five steps:
Step 1: Incision and access to the thyroid region (performed under direct vision)
Step 2: Section of the upper pedicle (performed endoscopically)
Step 3: Identification of the critical structures: the recurrent nerve and the parathyroids (performed endoscopically)
Step 4: Extraction of the thyroid lobe outside the neck and completion of the near-total or total lobectomy (performed under direct vision)
Step 5: Suture of the access point
Step 1. Incision and Access to the Thyroid Region
The operation starts with a 2 cm, midline incision in a skin crease on the same line of the conventional Kocher’s incision. This helps to maintain a satisfactory result in the case the operation needs a conversion to open surgery, when a short extension of the wound edges would convert the access to that of a conventional thyroidectomy.
Once the incision is made, the two smallest retractors should be positioned laterally. The “linea alba” should be carefully identified as in an open approach. The main challenge is correctly identifying it in this limited space. We recommend palpating the tip of the thyroid cartilage to help find the midline.
Once identified, the midline should be opened by means of conventional electrocautery for a limited extent. The short aperture of the strap muscles will help avoid excessive retraction on the skin edges, focusing the majority of the tension on the muscles themselves. This allows the skin edges to remain vital and results in a good cosmetic outcome.
After visualization of the thyroid gland, the operative space of one side should be entered with blunt dissection utilizing the spatulas. As in open surgery, the virtual space between the strap muscles and the thyroid lobe should be entered with the small retractors at first and then with the conventional army-navy after the posterior aspect of the thyroid lobe and the carotid sheath are visualized.
The correct positioning of the retractors is one of the key points of this operation. The lateral retractor should be retracting the carotid sheath and all its contents laterally (preventing an undesired thermal injury to those structures when the energy devices are used in the small operative space). The medial retractor should “hook” the thyroid lobe medially, while at the same time trying to slightly rotate it on the tracheal axis. The retractor should almost hide the lobe from the view of the endoscope (Fig. 6.1). The medial retractor mimics the role of the hand of the assistant during a conventional thyroidectomy. Be aware that, in this phase, the two retractors should always be placed in a symmetrical position, at the two edges of the incision.
Fig. 6.1
The medial retractor is used to “hook” the thyroid lobe toward the trachea while also rotating it out of the trachea-esophageal groove
Step 2. Section of the Upper Pedicle
This is the most challenging part of the endoscopic operation, and the only one step that is significantly different from the way it is performed in traditional surgery.
The largest retractors are still positioned on both sides of the incision. This positioning will be maintained throughout this entire step.
The endoscopic portion of the operation starts by introducing the tip of the endoscope through the incision to allow visualization of the operative field. The endoscope is a 30°, 7 mm in caliber scope that will initially be oriented caudally to allow division of the middle thyroid vein when present (Fig. 6.2a). Ligation can be achieved using either the energy instrument or a double clip (Fig. 6.2b).
Fig. 6.2
The endoscope, oriented caudally, allows direct vision of the middle thyroid vein (a). This vein is then divided (b)
Once this step is done, the endoscope can be rotated downside-up and, looking upward, the upper pedicle will be visualized at the top of the screen (Fig. 6.3).
Fig. 6.3
In order to visualize the superior pedicle vessels, after division of the middle thyroid vein, the endoscope is faced cranially
The upper pedicle is then sectioned in one step. Alternatively, based on the surgeon’s preference, the superior pedicle vessels can be divided individually. It is important to remember that for MIVAT, thyroid glands are of limited size, and consequently these vessels can be very small. Before sectioning the vessels of the upper pedicle, it is highly advised to carefully check for the presence of the branches of the superior laryngeal (or Galli-Curci’s) nerve. The superior nerve creates a loop at various heights of the upper pedicle or higher, heading medially to enter the lateral side of the cricothyroid muscle (Fig. 6.4a–c). The magnification provided by the endoscope, together with the view it allows of the cephalic aspect of the surgical field, permits this nerve to be seen when it is in its lowest positions (which is often not recognized during conventional thyroidectomy). Once the branches of the nerve have been visualized, their safety should be guaranteed by avoiding excessive heat exposure from using an energy device too close to them.
Fig. 6.4
The external branch of the superior laryngeal nerve can be visualized. This nerve can loop inferiorly to varying degrees (a–c)
Once the pedicle has been divided, hemostasis should be carefully verified. Any area of uncertain ligation should be immediately addressed for two reasons. Any acute bleeding can be very hard to manage endoscopically and can lead to undesired conversions. On the other hand, delayed bleeding can result in highly dangerous situations. As no drain will be left in the neck and the incision will be sealed, a spontaneous evacuation of the hematoma cannot be readily achieved.
Step 3. Identification of the Recurrent Nerve and the Parathyroid Glands
The great benefit of endoscopic magnification is the reason why this step is the easiest of the whole procedure. From conventional thyroid surgery, an experienced thyroid surgeon knows exactly where to search for the recurrent laryngeal nerve and the parathyroid glands. During MIVAT, having 20x magnification of these areas facilitates quick identification of these structures.
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