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Research Article, J Otol Rhinol Vol: 2 Issue: 3

The Evolution of Parathyroid Surgery

Emma Hoskison* and Mriganka De
Department of Otolaryngology, Head and Neck Surgery, Royal Derby Hospitals, UK
Corresponding author : Emma Hoskison
Department of Otolaryngology, Head and Neck Surgery, Royal Derby Hospitals, Derby DE22 3NE, UK
Tel: 07900 624187
E-mail: [email protected]
Received: March 07, 2013 Accepted: July 06, 2013 Published: July 15, 2013
Citation: Hoskison E, De M (2013) The Evolution of Parathyroid Surgery. J Otol Rhinol 2:3. doi:10.4172/2324-8785.1000130

Abstract

The Evolution of Parathyroid Surgery

Parathyroid gland discovery is accredited to Sir Richard Owen in 1850. Detailed studies on the glands included the work of eminent pathologist Virchow, helped to elucidate their physiology. The ‘glandulae parathyroideae’ were named in 1880 by Sandstrom from cadaveric studies. Surgery on the parathyroid glands was first performed in Vienna in 1925 by Mandl. A patient who had osteitis fibrosa cystica underwent a neck exploration for parathyroid adenoma. Since then, parathyroid surgery has developed, involving great surgical pioneers such as Bilroth, Kocker and Halsted in the early days and with a rapid evolution in the last decade. These recent advances can be attributed to a number of factors including increased specialisation and a trend towards minimally invasive surgery with a resultant reduction in hospital stay and improvement in neck cosmesis. Minimally invasive surgery has been achieved through advances in surgical techniques such as endoscopic video assisted dissection and robotic surgery using an axillary approach. The advent and implementation of new technologies such as radiological surgical guidance to help localise the pathological glands and the use of intra operative parathyroid hormone assay have also complemented these surgical advances.

Keywords: Parathyroid glands; Evolution

Keywords

Parathyroid glands; Evolution

Introduction

Discovery of parathyroid glands is accredited to Sir Richard Owen the Conservator of the Royal College of Surgeons. A rhino carcass was donated to him from London Zoo and following a careful dissection, a ‘yellow glandular body’ was identified attached to the thyroid gland [1].
The parathyroid glands were named by Ivar Victor Sandström, a Swedish medical student who dissected animal and human cadavers studying the small ‘hemp seed sized structure’ which he later named ‘glandulae parathyroideae’. This work was accepted and published in 1880 [2] however, the significance and function of this gland remained unrecognised.
Thyroid surgery was being undertaken in Europe during the time of Sandström’s discovery without full appreciation of the presence of the parathyroid glands. In 1879 Theodor Billroth performed a total thyroidectomy on a patient who had post operative complication of tetany. The aetiology of the convulsions was not recognised as hypocalcaemia and it was postulated that it was secondary to hyperaemia of the brain [3]. Kocher, another eminent surgeon who used a subcapsular technique for thyroidectomy was also operating in this era. His post operative tetany complication rates were lower than Billroth’s and Halsted postulated that this was attributable to a difference in operative technique [4]. The link with inadvertent parathyroid gland excision was not made.
The animal experiments of Professor Gley in Paris consolidated the link with parathyroid and thyroid gland removal and tetany which often proved to be fatal [5]. However it was the work of William MacCallum in 1909 whose experiments induced hypocalcaemia in dogs and produced a tetany similar to that seen in patients post parathyroidectomy, thus elucidating the role of the parathyroid glands in calcium metabolism [6].
In the early 20th century, case studies proved central to further understanding the role of the parathyroid glands and their endocrine function. In 1915 Professor Schlagenhaufer suggested that a solitary enlarged parathyroid gland in a patient could be the cause of bone disease and suggested excision for the mainstay of treatment [7]. However, neck exploration and parathyroidectomy was first performed in Vienna by Felix Mandl in 1925 [8].
Once the underlying pathological mechanisms were recognized, surgery became the main treatment for primary hypercalcaemia, developing from the origins in 1925. There is now a trend towards minimally invasive parathyroid surgery assisted with technological advances to achieve surgical “success” without compromising accuracy. Technical developments in the form of pre operative and intra operative investigations and surgical advances have assisted this evolution.

Investigations

Imaging of the parathyroids has an overall 90% sensitivity rate [9]. This is found to be higher when scintigraphy imaging is combined with dual phase, single photon emission computed tomography (SPECT) and dual tracer scintigraphy.
High resolution ultrasound imaging is important in the pre operative assessment of parathyroid surgery. Although operator dependent, it has the benefits of being non invasive and without radiation exposure. Its availability in the preoperative localisation of parathyroid adenoma alongside sestamibi scintigraphy and intra operative parathyroid hormone monitoring has produced confidence in the unilateral surgical approach with a “success rate” of unilateral surgery found to be 92.5% [10]. One of the benefits of preoperative scintigraphy is excluding ectopic parathyroid tissue which may include mediastinal, intrathymic and submandibular locations [11].
Technecium 99m-sestamibi is a radiopharmaceutical used in the diagnosis of abnormal parathyroid tissue. Each patient is injected pre operatively intravenously and after a defined delay of three hours to account for the half life of Tc-99m, probes can be used to assess the patient intra operatively. This helps to localise the pathology and survey the operative field pre excision of adenoma/carcinoma [12]. When compared directly with ultrasound scanning the sensitivity was found to be less (80%) [10]. However, pre operative investigations of sestamibi and ultrasound scans can be used in conjunction. If the results correlate well, there is a 94% chance of success of localising an adenoma in parathyroidectomy, hence contributing to the development of minimally invasive techniques [13].
One of the major advances in parathyroid surgery to be introduced is intra operative parathyroid hormone testing [14]. The PTH assay was developed in 1963 [15] and its use supports the surgeon in a minimally invasive approach. It is performed in a quantitative fashion with multiple samples taken from the patient during parathyroidectomy and comparisons made pre and post gland excision. This has achieved results of 94% sensitivity and overall 92.6% accuracy [16]. The surgeon can ensure that multiglandular disease is not present after excision of the adenoma and can also confirm that full excision of the adenoma has been achieved. However, the procedure is relatively expensive and time consuming.
Methylene blue was first introduced to stain abnormal parathyroid glands in 1917 [17] and hence is a potential adjunct for the sestamibi scanning in assisting localisation of the pathological parathyroid glands. Abnormal gland uptake with the dye is achieved with an intravenous infusion of methylene blue at a low dose of 5mg/kg [18] after anaesthetic induction. The basis for this selective uptake is not fully understood and its role in modern parathyroid surgery remains contentious. It may be used in conjunction with other techniques such as Tc 99m scanning as an additional localisation technique and has the benefit of being non toxic with minimally side effects and simple to administer [19]. The results of methylene blue uptake in abnormal parathyroid glands has been supportive of its use with a 100% uptake in a small study of 17 but Tc 99m has been shown to be successful in 69% of cases at pre operative localisation [19].

Surgical Techniques

The traditional surgical approach for primary hyperparathyroidism of bilateral neck exploration, which was first performed by Mandl in 1925, was the mainstay of treatment for hyperparathyroidism [20]. This extensive approach has now been replaced by increasingly selective surgery. In 1983, Pyrtek undertook unilateral neck exploration for hyperparathyroidism. Minimally invasive techniques were then developed alongside the increased accuracy of pathological gland localisation from high resolution ultrasound scan and increased sensitivity of 99mTc mapping. Chapuis et al. found a 90.5% “success” rate of unilateral neck exploration with only a 5.5% conversion rate to bilateral neck dissection using ultrasonography, sestamibi scanning and intra operative PTH monitoring [10].
In the last decade, the use of endoscopic [21] and video assisted techniques to perform minimally invasive parathyroidectomies have been introduced [22]. The utilisation of endoscopic technologies follows on from the development of Hopkins rod in 1960 [22] and allows for magnification of the anatomy up to 15-20 fold [21]. The instruments also allow for flexibility when exploring the mediastinum for ectopic parathyroid glands [21]. Patient selection, however, is important. Minimally invasive techniques are used in solitary adenomas in cases of hyperparathyroidism and therefore are not suitable for multinodular disease, malignancy or from failure of pre operative assessments to localise the pathology.
The first endoscopic subtotal parathyroidectomy was performed in 1995 [22]. A total of four portals were created under the platysma muscle and a 30 degree endoscope used after CO2 insufflation. The parathyroid glands were dissected and removed in the 5 hour operation and the patient had significant post operative emphysema from the eyelids to the abdomen which resolved by day three post operatively.
Minimally invasive video assisted surgery involves operating through a small incision of 1.5 cm in the suprasternal region (Figure 1). Endoscopes are passed through the incision after CO2 insufflation and dissection is preformed using microinstrumentation (Figure 2). The results from multicentre trials of this approach have been encouraging [22]. Minimally invasive video assisted parathyroidectomy (MIVAP) was performed in 109 out of 123 patients (89%) with conversion to open in 14 (11%). The reasons for failure included technological, failure of localisation of the adenoma or lack of a fall in intra operative parathyroid hormone. Post operative complications included hypocalcaemia in 7% of cases. There were no cases of permanent recurrent laryngeal nerve palsy after 6 months follow up. Limitations of the minimally invasive video assisted parathyroidectomies include the access and funding for the additional technologies required and the learning curve effect [22]. However, the additional expense maybe offset by reduction in operating time (94 minutes median) compared to endoscopic procedures and reduced hospital stay (mean 1.5 days). Patient satisfaction is also improved through a smaller scar resulting in increased comfort and better cosmetic results, although there is a lack of objective evaluation of these.
Figure 1: Incision markings for endoscopic parathyroid surgery.
Figure 2: Endoscopic view of superior parathyroid gland with recurrent laryngeal nerve. Clip pointing to gland.
Minimally invasive surgery can also be performed using endoscopes alone without video assistance. The complication results are comparable, but with increased emphysema and longer operating time for the purely endoscopic technique [23].
In the last decade, the use of robotic surgery has been used in selective cases for excision of ectopic parathyroids located in the mediastinum. One of the first procedures was described by Bodner and colleagues with pre operative CT-MIBI image fusion localising the ectopic parathyroid gland in the aorto-pulmonary window [24] and the DaVinici robot system was utilized via a minimally invasive approach. This pioneering procedure was uncomplicated and the operating view was considered to be superior than using conventional thorascopic surgery. Subsequent results show that although there have been only a select number of thorascopic mediastinal parathyroidectomies - Bodner et al. [25] reviewed only 38 between 1994 and 2002, results are encouraging with a 5% conversion to open and 8% complication rate. Case selection for these video assisted cases, however is important with pre operative imaging to localise the adenoma.
Despite technical advances, there is no substitute for surgical experience [26] and this has become more significant with the increased sub specialization with a majority of operations being performed by specialist endocrine or head and neck surgeons [27].
In the future there will be an increase in the diagnosis of primary hyperparathyroidism due to the aging demographic and hence a possible increase in parathyroid surgery. Minimally invasive parathyroid surgery increases possibility of local anaesthetic procedures [22]. Predictably, this would reduce hospital stay, with procedures in a day case setting. Unilateral parathyroid neck exploration is limited in cases of multigland disease which can comprise upto 15% of cases [28]. In these instances, bilateral exploration is the most common treatment option once parathyroid markers have failed to reduce after minimally invasive surgery.
However, it must be emphasized that patient selection for minimally invasive parathyroid surgery is central to its success. Future advances may include the increased use of robotic technology to produce more data.

Conclusion

Parathyroid surgery has developed far from its rudimentary origins in 1925 from bilateral neck exploration to minimally invasive procedures which reduce the surgical scar and hence increase patient comfort and satisfaction with an improved cosmetic result. Technological advances, including the use of pre operative high resolution ultrasound scanning and Tc 99m sestamibi scanning, assist the surgeon in localising adenomas in these minimally invasive approaches. Parathyroid hormone monitoring intra operatively has also supported the surgeon. Endoscopic development and video assistance has expanded the boundaries of this rapidly evolving field.

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