Student Authors:

Brian Burbidge, Kaya Garringer, Calder Dorn, Matthew Zeller, D.O.

BACKGROUND INFORMATION: The parathyroidectomy procedure is the removal of 1 or more parathyroid glands. The most common procedures are the open bilateral neck exploration and the open minimally-invasive approach. Additional minimally-invasive approaches have been developed, including video-assisted and endoscopic approaches, but have not become commonplace among surgeons.

A thorough understanding of the pathophysiology of hyperparathyroidism is key to comprehending the workup and surgical management of parathyroid disease. The parathyroid hormone (PTH) is produced by the chief cells within the parathyroid glands and is key in the maintenance of calcium homeostasis within the body.

Hyperparathyroidism is the overproduction of the parathyroid hormone. There are 3 different types of hyperparathyroidism (primary, secondary, and tertiary) that differ based on the cause of the increased PTH synthesis.

Of the 3 causes of hyperparathyroidism, primary hyperparathyroidism (PHPT) and tertiary hyperparathyroidism are commonly managed surgically. Many signs and symptoms of PHPT are nonspecific and may include bone pain, abdominal pain, fatigue, muscle weakness, and mood changes. Complications may include kidney stones and low bone density, though patients are often asymptomatic.

Primary hyperparathyroidism from parathyroid adenoma is genetically linked to MEN1 and MEN2A mutations. It is important to explore any personal or family history of disease associated with these hereditary conditions during the workup of patients with hyperparathyroidism.

In addition to hyperparathyroidism, MEN1 mutations also predispose patients to pancreatic neuroendocrine tumors and pituitary adenomas, whereas MEN2A mutations predispose to medullary thyroid carcinoma and pheochromocytoma.

NIH Criteria – Patient Must Meet at least One of the Following in the Presence of Elevated PTH:

• Age <50 year old
• Medical surveillance is not possible or desired
• DEXA T-score ≤-2.5, or vertebral fracture
• Serum Calcium >1 mg/dL above the ULN (10.3 mg/dL) or >11.5 mg/dL
• 24-hour Urine Calcium >400 mg (suspect with a history of kidney stones)
• Creatinine clearance <60 cc/min
  

An important contraindication to parathyroidectomy is familial hypocalciuric hypercalcemia (FHH), caused by a higher renal set point for calcium-sensing. This diagnosis can mimic PHPT upon initial laboratory evaluation (PTH is high normal in the presence of elevated calcium). In contrast to PHPT, FHH patients have normal kidney function and low 24-hour urine calcium levels. This diagnosis is not treated surgically and will lead to a failed treatment if parathyroidectomy is performed.

PROCEDURE DESCRIPTION: Minimally invasive open procedure. A transverse incision along natural skin folds is made over the isthmus of the thyroid gland, and the subcutaneous tissue is dissected with electrocautery.

Next, finger dissection is used to create the superior and inferior space. Care is taken to avoid the anterior jugular veins just ventral to the strap muscles and lateral to the median raphe. The median raphe is then divided to separate the right and left sternohyoid muscle, revealing the thyroid capsule deep to the strap muscles.

The dissection is continued deep and inferiorly to identify the inferior thyroid lobe with care taken to avoid injury to the recurrent laryngeal nerve (RLN). Once the nerve is located and observed coursing superiorly in the tracheoesophageal groove, the inferior parathyroid is located.

Focus is now turned to the superior parathyroid gland to ensure it is not enlarged. Again, care is taken to preserve the RLN. Once the diseased gland is identified, it is removed, sent for the frozen section, and a timer is started.

At 10 minutes following gland removal, an intraoperative PTH (iPTH) level is drawn. The operation is completed when the 10 minute PTH level drops 50% from the highest preoperative level following removal of the diseased gland (Vienna Criteria) and/or the iPTH is within the normal range (Miami Criteria 2,3). Hemostasis is ensured, the strap muscles are re-approximated, and the subcutaneous tissue and skin is closed.

For the bilateral neck exploration, after identification of one side of the parathyroid glands, the dissection is continued contralaterally to examine the remaining two parathyroid glands. This approach is most commonly used for multiglandular disease or when iPTH does not meet the Miami Criteria upon removal of the suspected diseased gland.

RISKS:

• General Surgical Risks (Bleeding and Infection).
• Risks Specific to Parathyroidectomy are Persistent Disease (This Procedure has 1-5% Failure Rates)
• Hoarseness Short Term Injury (10%) from Laryngeal Irritation and Swelling
• Longer-term Injury (0.3-3%) from Unilateral RLN Injury
• Hematoma (0.3%)
• Permanent Postoperative Hypoparathyroidism (0-3%)

KEY ANATOMY:

• Muscles
• Platysma
• Strap muscles
• Sternothyroid
• Sternohyoid
• Omohyoid
• Sternocleidomastoid
• Thyroid gland
• Thymus
• Parathyroid glands (x4)
• Superior parathyroid glands relation to the RLN
• Posterior to the RLN
• Inferior parathyroid glands relation to the RLN
• Anterior to the RLN
• Nervous structures
• Recurrent laryngeal nerve
• External branch of superior laryngeal nerve
• Vascular structures
• Common carotid artery
• Internal jugular vein
• Superior thyroid artery
• Inferior thyroid artery
• General Surgical Risks:
• Bleeding
• Infection
  

KEY LITERATURE:

• American Association of Endocrine Surgeons Guidelines for Definitive Management of Primary Hyperparathyroidism (Wilhelm, et al. 2016).

• Intraoperative PTH Monitoring Criteria: Miami vs Vienna Criteria (Barczyński, et al. 2009).

Read more about the procedure: @Western University

To watch the surgery live, click here: https://watch.giblib.com/video/7708