Parathyroidectomy

Hyperparathyroidism is generally treated by performing parathyroidectomy. It is important to determine whether surgery is indicated. Although hyperparathyroidism can produce symptoms (see hyperparathyroidism section), the disease is often discovered because of an abnormally elevated calcium level. This results in a workup to exclude a multitude of other causes of Hypercalcemia, and ensure the diagnosis is correct. A thorough history is obtained to exclude drug induced Hypercalcemia, or other medical conditions causing Hypercalcemia. In addition to electrolyte studies, parathyroid hormone (PTH) levels are obtained. Urine calcium levels are obtained, and bone density DEXA scans are obtained. Once the diagnosis is made, an attempt is made to determine if hyperparathyroidism results from a single adenoma or hyperplasia of the glands.

Diagnostic Imaging

Several diagnostic studies can localize the thyroid gland. Each has advantages and disadvantages:

Ultrasound. Ultrasonography performed by a skilled ultrasonographer can identify parathyroid adenomas. In addition, thyroid nodules are very common, and Ultrasonography prior to surgery will identify any thyroid disease that be evaluated prior to surgery, and if necessary removed at the time of parathyroidectomy. The main disadvantage of ultrasound is it is poor at imaging mediastinal adenomas.

Magnetic Resonance Imaging (MRI): MRI is very useful for localizing parathyroid adenomas. It does not use damaging radiation, and is very accurate when high quality imaging protocols are used, and a skilled radiologist interprets the studies.

Radionuclide imaging: The “sestamibi scan” is a radionuclide imaging study that has a high sensitivity for identifying parathyroid adenomas. The resolution of the study is low, but when combined with single photon emission computed tomography (SPECT), additional localizing information can be obtained.

4-D CT: 4D CT combines computed tomography (CT) with serial imaging after injecting intravenous contrast to identify the glands. Parathyroid adenomas rapidly enhance with contrast and have differential washout of contrast compared to lymph nodes and other structures in the neck. The main disadvantage of 4-D CT is the high radiation dose associated with this study. It is very useful for identifying recurrent disease or in cases where other imaging studies fail to localize an adenoma.

Venous sampling: Obtaining simultaneous blood samples from the lower internal jugular veins can localize the side of an adenoma based on different values of PTH when the samples are tested. This is generally performed at the time of surgical exploration.

Extent of Surgery

If a parathyroid adenoma is identified, it is removed, preserving the remaining parathyroid glands.) Some surgeons perform exploration of all four glands in every surgical case to visually inspect the glands. If an adenoma is identified, it is removed and the remaining glands are preserved. If hyperplasia is identified, 3 ½ of 4 glands are removed. Alternatively, some surgeons remove all 4 glands and reimplant a small piece of one gland in muscle of the neck or forearm.

An alternative approach embraced by many surgeons is localized exploration for adenomas. The adenoma is localized preoperatively, and excised. If this strategy is used, it is important to confirm that all abnormal tissue has indeed been removed. One approach is to measure intact parathyroid hormone level before, and 10 minutes after removing the adenoma. A drop in PTH level of over 50% is highly predictive of successful treatment. A second approach is to perform radionuclide measurements to confirm complete excision. Prior to surgery, radionucleotide is administered and sestamibi imaging is performed. At the time of surgery, a gamma counter is used to confirm removal of the adenoma and confirm absence of other areas of significant uptake in the neck.

Localized disease can be performed via a minimally invasive approach using a 2-3 cm. incision in the midline of the neck. In cases where the gland cannot be localized, or post excision PTH levels do not decrease, a search for additional abnormal glands is performed. If necessary, four gland exploration is performed.

Risks and Complications

Parathyroidectomy is most commonly performed under general anesthesia, although in selected cases the procedure is performed under sedation with anesthetic monitoring. Risks associated with general anesthesia are present, and related primarily to underlying medical condition of the patient undergoing surgery. Wound infection can occur, but is very uncommon following neck surgery. Bleeding into the neck can produce a hematoma that requires surgical drainage. On occasion, the skin can become tethered to the larynx, resulting in skin tethering. Hypertrophic scarring or keloids formation may also occur. The parathyroid glands lie adjacent to the recurrent laryngeal nerve, and is at risk of injury. Recurrent laryngeal nerve injury will produce a weak breathy voice. This is generally temporary, but can be permanent. Examination for vocal cord function is performed before and after surgery to document preservation of function, as injury may be associated with very subtle symptoms. When dissection is performed near the upper pole of the thyroid gland, the superior laryngeal nerve can be injured. This results in loss
of pitch range and decreased ability to produce loud voice (e.g. yelling).

In cases of severe hypocalcemia, removal of the parathyroid disease and normalization of the parathyroid hormone allows the bones to reabsorb calcium from the bloodstream, causing an acute drop in calcium. This is termed hungry bone syndrome. Hypocalcemia can also occur from trauma to remaining parathyroid glands, or excision of all parathyroid glands. This is generally temporary, but can be permanent. Treatment requires therapy with calcium supplements and vitamin D, and may also require magnesium replacement.

Failure to remove all diseased tissue or failure to identify the abnormal parathyroid tissue results in persistent hypocalcemia, and may require repeat surgical exploration.