2 The procedure
2.1.1 There are usually four parathyroid glands situated in the neck, but in about 10% of people one or more of the glands are located in the mediastinum. Parathyroid tumours (most commonly benign adenomas) can develop in any of these glands.
2.1.2 Parathyroid adenomas are a cause of primary hyperparathyroidism, characterised by the excessive production of parathyroid hormone, which results in high blood calcium levels. Symptoms and signs include tiredness, depression, confusion, constipation, polydipsia, polyuria, the development of kidney stones, bone pain and fractures.
2.1.3 The management of hyperparathyroidism may include dietary modification and the use of parathyroid hormone inhibitors. Surgical treatment may be required for some patients.
2.1.4 Parathyroid tumours situated in the neck can be removed surgically, usually through a cervical incision; however, tumours located in the mediastinum require a thoracotomy. Mediastinal parathyroid adenomas may also be treated by angiographic ablation or by computed tomography (CT)-guided ethanol ablation. Thoracoscopic excision of mediastinal parathyroid adenoma aims to reduce the morbidity and potential complications that may be associated with open procedures.
2.2.1 The location of the tumour is determined by imaging (for example CT, ultrasound or scintigraphy). Under general anaesthesia, a number of ports are placed in the intercostal spaces for the thoracoscope and instruments. One lung may be deflated to aid visualisation. The ectopic parathyroid gland is identified and dissected while keeping its capsule intact. The vascular pedicle is clipped and the gland is removed through one of the ports. A chest drain may be inserted. The ports are closed and the lung is inflated if necessary.
2.3.1 In three case series and five case reports, successful excision without conversion to open surgery was achieved in 100% (7/7, 4/4, 4/4, 3/3, 2/2, 1/1, 1/1, 1/1) of patients.
2.3.2 In one case series of four patients, the case report of two patients, and all three case reports of one patient, serum calcium levels were normalised in all patients shortly after thoracoscopic excision of mediastinal parathyroid adenoma. In the first single case report, a normalised serum calcium level (2.5 mmol/l) was maintained at 3-year follow-up. For more details, refer to the 'Sources of evidence' section.
2.3.3 The Specialist Advisers listed key efficacy outcomes as improvement in serum calcium and parathyroid hormone levels, histological confirmation of parathyroidectomy and low rate of conversion to open surgery.
2.4.1 One case report described a small apical pneumothorax following the procedure, which had resolved at 2-week follow-up.
2.4.2 A case series of three patients reported transient hoarseness in one patient, which was presumed to have resulted from damage to the left recurrent laryngeal nerve. For more details, refer to the 'Sources of evidence' section.
2.4.3 The Specialist Advisers stated that anecdotal and theoretical complications include bleeding, infection, chest wall pain, arrhythmias and catastrophic damage to the mediastinal contents, including the great veins and major arteries.