This is an exhaustive chapter on recently developed minimally invasive techniques for thyroidectomy, and primarily describes MIVAT. The role and results of this technique for the treatment of thyroid carcinoma are correctly described and discussed in depth, both from the technical and oncological points of view.
To recapitulate the goals described by the author of the minimally invasive thyroid approach, the technique should encompass the following criteria: (i) Surgical planes should be respected; (ii) access to the operative field should be close to the gland; (iii) scar tissue should not remain; (iv) trauma should be minimized; and (v) results of the minimally invasive technique must not be achieved at the expense of the patient’s safety.
On the whole, among the various recent minimally invasive/endoscopic approaches, MIVAT seems to represent the technique that most respects these criteria.
MIVAT was ideated and developed by Paolo Miccoli in Pisa in 1998, and from the very beginning of Miccoli’s experience, inclusion criteria for selecting patients undergoing MIVAT were established. These inclusion criteria are limited to the number of patients that can benefit from this approach, but which ultimately result in the patient’s safety, good postoperative recovery and excellent cosmetic outcome.
MIVAT can be performed in 10–15 % of thyroid cancer patients. Absolute contraindications include the following conditions: Thyroiditis, nodules >3 cm, cancers >2 cm, and cancers with the presence of lymph nodes metastases. In fact, if these contraindications are ignored, the cosmetic result and safety of the technique is compromised. Local implants after minimally invasive thyroidectomy have been reported; this could be related to morcelization of a large goitre, which undoubtedly does not represent a correct indication for MIVAT. Furthermore, the large volume of the thyroid obviously hampers safe dissection of important structures, such as the laryngeal nerves and parathyroids during the ‘endoscopic’ step of the procedure.
The majority of papers published on MIVAT report that no difference is seen in the complication rate between MIVAT and traditional thyroidectomy. However, these series (MIVAT versus conventional surgery) are, in fact, not statistically comparable; MIVAT series are constituted by selected patients, whereas the traditional thyroidectomy series usually range from small thyroid glands to large, intrathoracic or locally invasive carcinomas.
There is no doubt that MIVAT offers the following advantages:
Magnification of the target by employing the endoscope; this allows optimal visualization of the superior and inferior laryngeal nerves and of the parathyroid glands.
The possibility of exploring both sides with a small, unique, median incision
Less pain because the patient does not need neck hyperextension
An easy technique for general surgeons to learn, because it reproduces traditional thyroidectomy
The operation can be converted easily into a conventional open approach.
Small, non-aggressive tumours can be safely treated by MIVAT. However, the question arises of whether is it possible always to make this diagnosis preoperatively. All the important series on MIVAT show that a great number of tumours (of the less aggressive variety) are treated with this approach and that the same survival rate is achieved as with traditional thyroidectomy. One criticism that could be raised is that the median length of follow up (5 years) reported in the largest series is not enough to exclude recurrence when dealing with this type of neoplasia. The literature documents that differentiated thyroid cancer has a long survival with a low recurrence rate, independent of the type of surgical treatment. Nevertheless, as reported by Miccoli et al., despite the fact that a longer follow up is necessary before drawing any final conclusions, the first 5 years from the diagnosis of papillary carcinoma and initial treatment are those with the highest risk of recurrence.
Temporary laryngeal nerve palsy rate after MIVAT appears to be higher than that after traditional thyroidectomy. This is not due to an excessive traction on the nerve during the extraction of the lobe, if the nerve has been properly dissected during the endoscopic phase, but might be caused by improper utilization of energy devices, such as ultrasonic scissors employed during the operation. It is well known that the minimal distance of the active blade must be >5 mm. When necessary, a vascular clip is preferable when dealing with small vessels close to the nerve, in order to achieve total removal of thyroid tissue, instead of leaving a remnant in order to ‘preserve’ the nerve.
All authors underline better cosmetic results with MIVAT. Of course, a blind trial is impossible.
The traction on the skin makes contusion of the verges mandatory, thus causing the premise for a suboptimal scar. The decision is to perform a smaller but a more ‘worked out’ incision or longer incision (comprising contused margins).
One of the advantages of MIVAT is the reduction of postoperative pain; it is expected that both the absence of neck hyperextension and more limited dissection concur in this aim. A prospective, randomized study was designed to demonstrate objectively that MIVAT minimizes postoperative pain. TGF-β serum levels immediately after surgery seem to correlate with levels of pain, confirming that reduced postoperative distress is an objective of MIVAT. This result confirms the results of studies based only on subjective pain evaluations (Miccoli et al. Surg Endosc 2010).
As for the disadvantages of the technique, the following must be considered:
There must be three surgeons—one for the camera, one for retractors and the operator.
The learning curve needs at least 30 procedures.
I agree with the author that the most common mistake of MIVAT is an incorrect selection of patients.
Can we consider minimally invasive procedures by the transaxillary or the breast approach to the thyroid—or even TOVAT (transoral video-assisted thyroidectomy)? All these procedures look cumbersome; some need carbon dioxide insufflation, similar to one of the first attempts by Gagner, with a prolonged stay in the recovery room. All this effort is made to avoid a scar in the neck by paying the price of a demanding (and possibly risky) procedure.
MIVAT is a technique in some ways equivalent to single port access in abdominal laparoscopic surgery; a minimally invasive approach becoming increasingly popular. Some new instruments will probably be employed (or modified) for thyroid procedures.
About the future evolution of this field, it is hoped that evolution of robotic arms will broaden the indications for MIVAT.
Finally, one more application for MIVAT is the sentinel node study procedure with the preliminary injection in the tumour and localization of the sentinel node.