In the past, parathyroidectomy involved an open procedure with a neck incision not unlike that used for a thyroidectomy, and it required the inspection of all 4 parathyroid glands, with removal of the offending gland or glands. Its major indication is for primary hyperparathyroidism, and usually the largest parathyroid was suspected and removed. Eventually, the use intraoperative physiologic studies improved the likelihood that the offending gland or glands were removed. Concurrently, there has been a push from the public as well as within the surgical community for less and less invasive procedures, with a goal of decreased recovery time, increased cosmesis, and decreased operative time and complications.
This article discusses minimally invasive techniques for parathyroidectomy (MIP) with a focus on minimally invasive radioguided parathyroidectomy (MIRP).
A detailed description of the relevant embryology and anatomy can be found in Parathyroid Gland Anatomy. The parathyroids are derived from the third and fourth pharyngeal pouches. The inferior parathyroids come from the third pharyngeal pouch and follow the descent of the thymus until they rest on the dorsal surface of the thyroid, usually in a plane anterior to the superior parathyroids. In contrast, the superior parathyroids develop from the fourth branchial arch and descend into the neck with the thyroid gland.
There are usually 2 glands on each side of the thyroid, although 3-7% of the population may have an accessory (or supernumerary) parathyroid, and 3-6% may have fewer than 4 glands. The glands may occasionally descend incompletely, or too far, and lie in aberrant locations, including the anterior or posterior mediastinum, the bifurcation of the carotids, or in the retroesophageal, retropharyngeal, or retrolaryngeal regions. The inferior thyroid artery usually provides the vascular supply for both the superior and inferior parathyroid glands, although 20% of superior parathyroids may be supplied solely by the superior thyroid artery.
Intrathyroidal parathyroid glands are described, although there is some controversy surrounding their existence. Some state that these parathyroids are not truly within the thyroid but instead are extracapsular, with the thyroid surrounding it. Others describe true intrathyroidal parathyroids with an incidence of 0.5-3%.
The primary indication for a parathyroidectomy is primary hyperparathyroidism. Classically, these patients are referred to an otolaryngologist’s practice from either the primary care physician or endocrinologist.
These patients are described as having signs and symptoms following the mnemonic “bones, stones, groans, and psychiatric overtones”—including skeletal complications (pathologic fractures, osteitis fibrosa cystic, osteoporosis), renal disease (nephrolithiasis, nephrocalcinosis, diabetes insipidus, renal failure), gastrointestinal symptoms (constipation, nausea, vomiting), and psychiatric (mood swings, depression, psychosis) and central nervous system (lethargy, ataxia, delirium) manifestations.
Many patients, however, present only with signs of elevated serum calcium and parathyroid hormone (PTH) levels and subtle symptoms of fatigue, depression, emotional lability, joint pain, or abdominal pain.
Previous radiation exposure to the head and neck has been a listed contraindication to minimally invasive procedures, secondary to the increased risk of multiglandular disease and the possibility of coexisting thyroid cancer.
However, Rahbari et al performed a prospective cohort study to determine the effectiveness of MIP, and they show no significant differences between the presence of concurrent thyroid diseases, multigland parathyroid disease, or eventual operation chosen between the cohort that had a history of head and neck radiation and the cohort that had no exposure to radiation.
For patients with multiglandular disease, a minimally invasive approach may not be practical or indicated. Additionally, it is important to distinguish patients with familial hypocalciuric hypercalcemia from patients with true primary hyperparathyroidism, as the first group would not benefit from a parathyroidectomy.
As part of the preoperative planning for MIP, it is important to localize the offending parathyroid gland. At the authors’ institution, patients undergo a double-phase technetium Tc-99m (99m Tc)
sestamibi scan, either alone or as 3-dimensional nuclear imaging fused with CT of the neck (single-photon emission computed tomography [SPECT]) preoperatively.99m Tc sestamibi is a radiotracer that is localized by the mitochondria of the parathyroids, and, by performing a delayed scan, those parathyroids with retained tracer are concerning for adenoma.
A recent meta-analysis by Cheung et al compared a variety of imaging studies to aid with localization and determined that SPECT had a pooled sensitivity and positive predictive value of 78.9% and 90.7% based on 9 studies, with a range of sensitivities between 61.4% and 100% in the studies analyzed. For patients who localize to one gland, MIP is offered, with the caution that a parathyroid exploration may still be necessary based on intraoperative findings.
Miyabe described the use of 3-dimensional ultrasonography, which provides coronal images similar to a surgeon’s view, and determined a lower operative time when compared with traditional 2-dimensional ultrasonography.
Aside from the use of a radioactive tracer, ultrasound is commonly used to identify parathyroid adenomas, although its use is subject to operator technique and interpretation. Sensitivities ranged from 48.3-96.2% in the studies analyzed in the meta-analysis by Cheung et al. The pooled sensitivity for ultrasound based on 19 studies was 76.1% and 93.2%, respectively.
Another novel approach described by D’Agostino et al was recently published and used a 3-dimensional rendering of a CT scan that is then used intraoperatively to help with localization. The patient has a CT scan performed with neck extension and the rendered scan is overlaid over a visual image of the patient’s neck in the operating room. A separate technician is used to aid with manipulation of the rendered scan as it pertains to the operation. The authors describe a 77.2% and 64.9% accuracy of the CT scan with regard to correct identification of laterality and location, respectively.
The reported outcomes from parathyroidectomy for primary hyperparathyroidism are very positive, with success rates nearing 100%. Adil et al reported 100% of patients who underwent MIP had a hyperfunctional parathyroid identified and excised, with appropriate drops in intraoperative PTH levels.
Beyer et al reported 100% rates of eucalcemia (cure) at 3 months amongst bilateral neck exploration and 99% amongst MIP surgery, with 1 failure. Additionally, they found lower costs, operating time, and length of stay in the hospital to be associated with the minimally invasive approaches.
A more recent review by Schneider et al found no difference in outcomes between minimally invasive and open approaches, with the exception of increased transient hypocalcemia in the open approach group (1.9% vs 0.1%).
Leder et al reviewed the laryngeal physiology and acoustics of patients before and after MIP surgery and found not differences amongst a variety of parameters.