Traditionally parathyroidectomy involves a collar incision, bilateral exploration of the neck, identification of all four parathyroid glands, and removal of the diseased gland or glands. This approach, in experienced hands in large volume centres, has enabled cure rates of up to 97% with minimal morbidity, although a cure rate of 70% probably reflects general surgical practice more faithfully.^4,5 More than 80% of patients with primary hyperparathyroidism have a solitary adenoma, removal of which guarantees cure. In the 1980s a unilateral approach (through a collar incision) was advocated, based on the principle that removal of the single abnormal gland in the presence of an identified ipsilateral normal gland avoided the need for a contralateral exploration.⁶ Despite its enthusiasts this approach failed to gain universal support because of concerns over the reliability of the localisation procedures available at the time and the possible presence of undetected double adenomas or asymmetrical hyperplasia.

The lack of a consistently reliable method for localising parathyroid tumours hampered the introduction of minimal access approaches to parathyroid disease. Thallium-technetium subtraction scintigraphy is dependent on the size of the adenoma, and ultrasonography of the neck is operator dependent.⁷ The arrival of technetium-99m sestamibi scanning has revolutionised preoperative localisation of parathyroid glands. It accurately identifies the side and site of the parathyroid tumour in up to 88% of cases. When used in combination with ultrasonography 98% of solitary adenomas are localised, although concordance is found only in approximately two thirds of all primary hyperparathyroidism.⁸

Patients with accurately and reliably localised single gland parathyroid disease may be treated with a minimal access approach. Various minimal access techniques have been advocated, including a videoscopically assisted and an entirely endoscopic approach. However, they have not been widely adopted. The minimally invasive parathyroidectomy is achieved through a 2 cm skin incision placed over the appropriately localised parathyroid gland. Minimally invasive parathyroidectomy can usually be done in less than 20 minutes, with a local anaesthetic cervical block and sedation or laryngeal mask airway, often as a day case procedure. The operation is performed without compromising the established principles of avoiding a parathyroid capsular breach and identification and preservation of the recurrent laryngeal nerve although the nerve may not always be in the operative field. Minimally invasive parathyroidectomy is currently the procedure of choice for 92% of members of the International Association of Endocrine Surgeons favouring a minimal access approach.⁹

Large series comparing minimally invasive parathyroidectomy with a conventional neck exploration have shown a 50% reduction in operating time, a shorter hospital stay, and a comparable clinical outcome with no notable difference in the type or number of complications.¹⁰ However, whether such commendable results may be extrapolated to surgeons who operate on the parathyroid only occasionally and are unfamiliar with the lateral neck approach remains to be seen. One “complication” that is exclusive to all minimal access approaches is that of conversion to a standard cervicotomy, which affects approximately 4% of minimally invasive parathyroidectomy patients and 8.1% of those undergoing a video assisted minimal access technique.¹¹

The intuitive economic benefits of minimally invasive parathyroidectomy remain debatable since the shorter operating time and hospital stay (day surgery) are balanced by the cost of preoperative localisation in all patients (including those with unsuccessful parathyroid localisation) and the use of intraoperative parathormone measurements.¹² Intraoperative parathormone measurements are considered by some to be a complementary safeguard to successful localisation of the parathyroids, but this contributes heavily to the cost of surgery and carries a small but significant false negative rate. In at least one large centre as well as the authors' the use of intraoperative parathormone measurements in primary surgery has been abandoned because they are not cost effective.¹³ It remains unproved, however, that the removal of intraoperative parathormone measurements from the operative costs makes a minimal access approach beneficial in terms of cost compared with a conventional parathyroidectomy, although this is likely.

Minimally invasive parathyroidectomy is possible only in those patients in whom a single adenoma can be concordantly localised by using ^99mTc sestamibi scanning and ultrasound—just over 60% of patients. This, however, represents 80% of all patients with a single adenoma. Patients with unlocalisable disease or multiple gland disease are unsuitable for this technique and require a conventional neck exploration. Equally minimally invasive parathyroidectomy is contra-indicated after previous neck surgery and in patients with concomitant thyroid disease, but increasingly these contraindications are considered relative rather than absolute.