Parathyroidectomy

Minimally Invasive Parathyroidectomy (MIP)

Fig.1: Typical MIP incision approx. 2cm in lengthThe procedure is performed under general anaesthesia with an endotracheal tube. The surgeon should always wear a headlight as the wound will be small and deep. The patient is positioned supine on the operating table, with the head of the table elevated. A bolster is placed behind the shoulders, and the head supported on a rubber ring.

Having previously marked the site of the abnormal parathyroid, the neck is cleaned with antiseptic and a 2 cm incision is made through skin and platysma, preferably in the line of a skin crease (Fig. 1).

The incision is placed on the side of the localised parathyroid, approximately a finger's breadth above the sternoclavicular joint. The incision is so small that the anterior jugular veins are easily avoided and rarely damaged.

The skin and platysmal flaps are raised above and below the incision to allow maximum mobility of the wound.

Fig.2: 'Back-door' approach to parathyroid tumourAn incision is now made along the anteromedial edge of the sternomastoid muscle, to allow separation from the strap muscles’ lateral edge. This is the so-called ‘back-door’ approach, which gives excellent access to the parathyroid and the recurrent laryngeal nerves (Fig. 2).

Divide the omohyoid muscle, if it is in the way, as it runs over the internal jugular vein and then if necessary the sternohyoid and sternothyroid can be divided very low in the neck, but this is rarely needed with good retraction.

The muscles are separated with a combination of sharp and blunt dissection, the carotid sheath is located and retracted laterally. Further mobilisation in the area between the trachea and carotid sheath is undertaken, and the recurrent laryngeal nerve will usually become obvious in this area and should be sought at this point. The thyroid will form the medial edge of the field and may need to be separated from the overlying strap muscles to make the anatomy clear.

Now attention is turned to locating the parathyroid tumour, which in fact may already be obvious with this approach. Upper parathyroids are quite constant in position, 80% lying within a 2cm radius of the point where the inferior thyroid artery crosses the recurrent laryngeal nerve. On rare occasions enlarged upper parathyroids may be found behind the oesophagus and even in the posterior chest.

Fig.3: RLN (arrowed) adherent to large parathyroid adenomaLower parathyroids are found anterior to the plane of the recurrent laryngeal nerve but are more variable in their position. In most cases however the dissection is straightforward and the parathyroid tumour found within a short time of opening the neck. Be aware that a lower parathyroid tumour may be adherent to the undersurface of the strap muscles and so may be under the retractor.

Once located, the parathyroid tumour is carefully dissected free from surrounding structures to avoid any disruption to the tumour, which may lead to parathyromatosis (see below). This is best achieved by blunt technique, such as using a peanut, avoiding picking up the tumour with forceps, which can lead to rupture. Careful use of the ligasure to divide attachments and the pedicle is very safe.

At all times it is vital to keep the recurrent laryngeal nerve in view to prevent damage, as occasionally the nerve can be found draped across the tumour (Fig. 3), and in danger of accidental damage.

When the tumour is free all around, the RLN located, and the feeding vessel isolated, a ligaclip or ligasure sealing device can then safely be placed across the vascular pedicle.


Thyroid pathology

Pathology in the thyroid is common in patients with parathyroid disease, although the preoperative ultrasound will alert the surgeon to this; it should be dealt with on its merits with the liberal use of FNA cytology prior to surgery and rapid section pathology (frozen section) intraoperatively. Thyroid pathology should not be a surprise at operation, and a strategy for dealing with it should be devised before picking up the scalpel.

Dealing with the parathyroid pathology

Single adenoma

Removal of the well-localised adenoma by a focused approach will cure the patient in the vast majority of cases. It is not necessary to biopsy normal glands, or to inspect all four glands, as there is usually only one gland hyperfunctioning.

Primary parathyroid hyperplasia

One of the more difficult conditions to diagnose preoperatively is primary parathyroid hyperplasia or asymmetric hyperplasia, a condition to be expected in the secondary and tertiary HPT patients. With the advent of better localisation and focused surgery, hyperplasia has been diagnosed much less commonly than before, suggesting that over-diagnosis at four-gland exploration may have occurred in the past.

Hyperplasia may affect 2 or more glands, and extra glands are common, making routine cervical thymectomy mandatory. The aim of surgery is to have a normocalcaemic patient with no calcium or vitamin supplements. This can be achieved by either subtotal parathyroidectomy leaving a small amount of tissue in situ or by parathyroid transplantation. The long term results are not nearly as good as in surgery for single gland disease, and it is worth making the following points:

  • If undertaking parathyroid transplantation, make sure that all parathyroid tissue has been excised. There is no more difficult situation to sort out than graft-dependant recurrent hyperparathyroidism versus missed functional parathyroid tissue in the neck or mediastinum.
  • If undertaking subtotal parathyroidectomy, remove 3 glands and leave 125-150mg of parathyroid tissue. Leave a gland that lies well away from the recurrent laryngeal nerve (usually a lower gland, which lies in front of the plane of the nerve) and mark it with a ligaclip or prolene suture. 
  • A pragmatic view would be to perform total parathyroidectomy with life-long calcium and vitamin D supplementation in the following patients: those over 50 with or without severe hypercalcaemia, and those patients under 50 with severe hypercalcaemia. The supplementation is no great hardship and very easy to control. It is probably mandatory in the MEN1 syndrome, where it is so important that the parathyroid aspect of the disease is under perfect control, however new strategies for the surgical approach involving MIP have recently been described. Patients over 50 with moderate hypercalcaemia, and who are not MEN 1 syndrome patients, should undergo subtotal parathyroidectomy.

Double adenoma

This is probably just a variant of asymmetric hyperplasia and should be treated on its merits, removing only the enlarged glands, with frozen section confirmation.

Secondary parathyroid hyperplasia

In the case of secondary hyperparathyroidism, usually due to renal disease, the approach depends on surgeon and nephrologist preference, the experience of the surgeon, the comorbidities and life expectancy of the patient, and the likelihood of renal transplantation.

There are a number of things to remember in these patients: 

  • consider the use of frozen section (to ensure success)
  • decide on which glands are to be removed when they have all been found and while they are still all in situ
  • ensure there is a viable remnant in a subtotal parathyroidectomy
  • gland selection - leave part of a smooth hyperplastic gland, not a nodular one
  • always clear one side of the neck in a subtotal parathyroidectomy
  • always perform thymectomy (as parathyroid rests in the thymus are common)
  • mark the remnant with a clip or suture (and prefer leaving part of a lower gland, as more anterior)
  • autograft to the brachioradialis
  • always insert CVC line for calcium management after operation 

Parathyroid cancer

Fig.4: Mass in the neck of parathyroid cancerMost cases of parathyroid cancer are not actually cancer at all, but atypical adenomas. In any case they tend to be very functional, the clues to the diagnosis being a very high calcium and PTH, young age, a mass in the neck (Fig. 4), voice change and of course, evidence of metastases.

Further detail can be found on the webpage Parathyroid Cancer.

There are 2 separate situations:

  • Following removal of a single adenoma which appeared benign at surgery the final histology sections suggest malignancy (both calcium and parathyroid hormone levels having returned to normal).
    In these cases the patient should be not be re-explored, unless the calcium and PTH levels begin to rise later, suggesting recurrence. In this case a hemithyroidectomy should be performed on the side of the tumour, with meticulous clearance of the local areolar tissue and lymph nodes. 
  • In a patient with severe hypercalcaemia where a hard mass is found, the mass itself and the ipsilateral thyroid and local lymph nodes should all be excised en-bloc, if necessary sacrificing the recurrent laryngeal nerve.
    Postoperative external beam radiotherapy is of little benefit, and chemotherapy is of little value.
    Most deaths are due to uncontrollable hypercalcaemia resistant to bisphosphonates, but Cinacalcet (a calcimimetic) can successfully control this in most cases.

Disrupted parathyroid syndrome (parathyromatosis)

Fig.5: CT scan of deposit of parathyromatosis in the neck musclesParathyroid tissue can readily reimplant and grow to functional size if spilt in the neck at the time of parathyroidectomy.

This phenomenon is exploited deliberately for parathyroid autotransplantation, but is a problem when adenoma tissue is inadvertently spilt at the time of resection, as recurrence is possible if the spilt tissue regrows (Fig. 5). 

When exploring such patients with recurrent hyperparathyroidism due to parathyromatosis, small millet seed-sized nodules can be found at the site of the previous parathyroidectomy. These nodules are minute pieces of disrupted parathyroid that have regrown. They must be completely excised with the surrounding thyroid tissue and any involved muscle.