Patients with sporadic pHPT in whom a single adenoma is suspected based on preoperative imaging studies (MIBI-scan and ultrasonography) are ideal candidates for MIVAP. Parathyroid adenoma larger than 3 cm is usually excluded because of the theoretical risk of capsular rupture and consequent parathyromatosis due to difficult dissection and extraction [26, 27].

At the beginning of the experience exclusion criteria included previous neck surgery, persistent or recurrent hyperparathyroidism, mediastinal adenomas, and concomitant large goiter. With the increasing experience, selection criteria for MIVAP have been widened. Patients with concomitant nodular goiter can undergo MIVAP if the usual inclusion criteria for the video-assisted thyroidectomy are met [28]. Moreover, in selected cases, patients with previous neck surgery or intrathymic/retrosternal adenomas can be selected for MIVAP. Because bilateral neck exploration is possible through the same access, MIVAP can be performed both in patients with suspected multiglandular disease and in patients with uncertain preoperative localization [27].

The rate of patients with sporadic pHPT who are candidates for MIVAP varies (37–71 %) [15, 26] due to different incidence of coexisting thyroid diseases that may require a conventional approach [15].

MIVAP has been proposed also for patients with four glands hyperplasia (i.e., familial pHPT and secondary and tertiary hyperparathyroidism) [21–30]. However, these indications, in our opinion, still need to be confirmed and validated by larger series and comparative studies.

Conversion rate is highly variable ranging from 0.9 % [15] to 25 % [31]. The more frequent indications to conversion are bleeding, inadequate IO-PTH decrease, false preoperative localization, difficult to localize/dissect the parathyroid adenoma(s), suspicious of malignancy, and ectopic localization of the pathologic gland. Proper patient selection and surgical team experience are able to lower the conversion rate even in regions with reported endemic goiters [15, 28].

Also the operative time strongly depend on surgical team skill and experience. Indeed, it has been demonstrated that the operative time decreases significantly with increasing experience and it is comparable or even shorter than that of conventional operation [15, 26, 32].

Several large retrospective series have reported on the short- and medium-term outcome of MIVAP. In 350 cases of MIVAP in 6 years, Miccoli et al. [26] reported a cure rate of 98.3 %. At a medium follow-up of 35.1 months, 4 patients had persistent disease due to false-positive IO-PTH. Complications occurred in 14 patients: 2.7 % transient hypocalcemia, 0.8 % permanent nerve palsy, and 0.3 % postoperative bleeding [26]. Others have reported similar results in smaller series [21, 23]. In our previous published series of 107 cases of MIVAP we reported a success rate of 98.1 % with persistent disease in 2 patients (1.9 %) [15]. We reported a 11.1 % rate of temporary hypocalcemia with no permanent hypoparathyroidism, and no other complications [15].

MIVAP presents some technical advantages compared with other endoscopic or video-assisted techniques [27]. First of all, this technique combines the advantages related to the endoscopic magnification with those due to its similarity with the conventional surgery. Indeed, the operative procedure reproduces all the steps of the open procedure. The excellent visualization of the neck structures due to the 2–3 fold endoscopic magnification permits easy identification of the laryngeal nerve and parathyroid glands. In a recently published prospective randomized trial, the mean time for adenoma localization was significant shorter for the group of patients who underwent MIVAP compared with patients operated on with an open minimally invasive technique [7].

Another merit of the technique is the possibility to perform a bilateral neck exploration when necessary through the same central access. This characteristic in part explains the very low conversion rate reported in different series [15, 26]. The possibility to perform a bilateral neck exploration produces two main effects on the restrictive inclusion criteria. Indeed, MIVAP can also be performed in case of unavailability of intra-operative PTH monitoring or in case of inadequate preoperative localization studies, because of the possibility to explore all the parathyroid sites [15, 33]. Another advantage of the central access is the possibility of associate thyroid resection, even bilateral, when necessary. Because of the high prevalence of multinodular goiter in some countries, this technical characteristic allowed experienced surgeons to increase the rate of patients eligible for a video-assisted procedure in selected patients. In our experience, with the high prevalence of goiter in Italian population, this allowed us to treat both thyroid and parathyroid diseases simultaneously in more than 30 % of the patients [28].

Moreover, the video-assisted access could imply a better cosmetic result and a less postoperative pain. Indeed, several comparative studies have demonstrated the advantages of MIVAP to reduce the postoperative pain, improve the cosmetic result and the patient satisfaction over both conventional and open non-endoscopic minimally invasive parathyroidectomy [7, 8].

Some criticisms about technical aspects for MIVAP still exist and are mainly related to the operative time. However, it has been demonstrated in large retrospective series [15, 26] and also in small comparative, randomized trials [7] that the operative time does not represent a limit.

Another technical problem is the number of members of the surgical team. The fact that two assistants are necessary to accomplish the MIVAP can represent an important concern for the application and diffusion of the procedure, at least in some surgical setting.

On the other hand, the main technical limitation of MIVAP is still represented by the volume of parathyroid adenoma and of the eventually associated goiter. Dissection and extraction of large adenomas through a small incision can result in capsule rupture with the theoretical risk of parathyromatosis [15]. In contrast, previous neck surgery and the absence of a clear preoperative localization are not contraindications for MIVAP.

In spite several reports have demonstrated that thyroid and parathyroid procedure are safely performed by residents operating under supervision and newly established surgical consultant, there is a significant inverse relationship between the number of procedures performed and the complication rate [34]. In other words patient volumes and surgical skill play an important role in reducing complications rate, as in other fields of surgery.

Obviously, lower complications rate are obtained in third care referral centers, where dedicated surgical teams and well-trained endocrine surgeons are provided and hospital facilities allow adopting all the measures and tools known by the medical community as the gold standard for patients treatment.

When the procedure is performed under optimal conditions combined with meticulous operative skill by surgeons who have been adequately trained, the incidence of complication should be at a minimum [34]. Nonetheless, complication may occur, not only because of surgical errors, but also for factor related to the patients or the disease itself.