Head & Neck Surgery

Introduction

Under normal circumstances, the blood calcium is kept within the normal range by a hormone from the parathyroid glands. There are usually four parathyroid glands (two on either side of the neck) located on the posterior aspect of the thyroid gland. The main action of parathyroid hormone (PTH) is to raise the calcium blood level by releasing calcium from the bones. Parathormone also increases the absorption of calcium through the intestinal tract and effects the amount of calcium excreted through the urine, but these are secondary functions compared to the effect on the bones. The release of PTH is controlled by the serum calcium level. When the serum calcium level falls, the PTH level rises, which, in turn releases calcium from the bones to maintain the normal blood calcium level. When the calcium blood level is elevated, the parathormorne level should be low.

The calcium blood level may be altered by a number of factors. Diet, medications, and vitamins (A & D) may cause elevation of the serum calcium level. Dehydration may artificially raise the calcium level because of hemoconcentration. Kidney function effects the calcium level by controlling the amount of calcium excreted in the urine. Certain malignancies may cause hypercalcemia, either by secondary tumors in bone, resulting in the discharge of calcium in the blood, or by making a parathormone-like substance which causes calcium release from the bones.

The most frequent cause of hypercalcemia in the United States today is hyperparathyroidism. An estimated 100,000 new cases of hyperparathyroidism are seen in this country each year. This condition occurs 3-4 times more often in females than males and increases with age.

There are three types of hyperparathyroidism: primary, secondary and tertiary.

• Primary hyperparathyroidism is caused by single or multiple adenomas, hyperplasia (which involves all parathyroid glands) or parathyroid cancer. Eighty-five to ninety percent of primary hyperparathyroidism is due to a single parathyroid adenoma. Hyperplasia, represents 6-8 percent of primary hyperparathyroidism; multiple adenomas 4-6 percent; and parathyroid cancer is extremely rare, representing only 1 or 2 percent.
• Secondary hyperparathyroidism is an occasional occurrence in individuals with chronic renal failure and is the normal response of the parathyroid glands to the low blood calcium. Continued calcium excretion through the kidneys occurs because the concentrating capabilities are damaged in chronic renal failure.
• Tertiary hyperparathyroidism occurs in renal failure patients and represents the establishment of autonomous abnormal parathyroid production due to the chronic parathyroid stimulation of the hypocalcemia.

Diagnosis

Today most patients with primary hyperparathyroidism are identified incidentally by a multi-channel chemical blood analysis. Symptomatology of primary hyperparathyroidism includes the five classical groups of symptoms; painful bones, kidney stones, abnormal groans, psychic moans, and fatigue overtones. Table 1 shows frequency of different symptomatology. The diagnosis of primary hyperparathyroidism depends upon:

1. repeated documentation of hypercalcemia,
2. the exclusion of external causes of hypercalcemia, (such as high doses of vitamins A or D or large amounts of calcium containing substances,
3. normal kidney function,
4. the exclusion of malignancy,
5. parathormone (PTH) assay levels in-appropriately elevated in relation to concurrently determined serum calcium.

Elevated calcium and elevated PTH is a clear indication of hyperparathyroidism, an abnormal circumstance. Hyperparathyroidism may present with an elevated PTH and a normal calcium because of effective renal function resulting in excretion of the high blood calcium in the urine. Elevated urinary calcium and osteoporosis may also be seen.

Treatment Options

Treatment for most patients with either primary or tertiary hyperparathyroidism is surgical exploration of the neck with removal of the abnormal gland or glands. While neck exploration in experienced hands is in the 95 percent range, all patients diagnosed with  primary hyperparathyroidism are not necessarily candidates for surgery. Symptomatic hyperparathyroidism, severe hypercalcemic crisis, recurrent renal calculi with impairment of renal function, and progressive metabolic bone disease with bone mass loss are clear indications for surgery. Patients with asymptomatic hyperparathyroidism with calcium above 12 mg/dl and those under 50 years of age are considered candidates for surgery because of calcium levels or because of the long-life expectation and potential for long-term effects of hypercalcemia. Asymptomatic hyperparathyroidism patients with less severe disease and in older age groups may be managed with medical therapy without the necessity of a surgical exploration.

Preoperative Localization

In our view, preoperative imaging studies are of limited value in patients with tertiary hyperparathyroidism who will undergo bilateral exploration because of the expectation of multi-gland disease. When unilateral exploration is considered an option in untreated patients with primary hyperparathyroidism, we feel that preoperative imaging is helpful in guiding the surgeon to the side of the neck most likely to harbor the dysfunctional gland. As the effects of "health care reform" are lowering the cost and reimbursement for preoperative imaging studies, these are actually becoming more cost effective.

The technetium sestamibi scan is a radioisotope scan which represents the most reliable preoperative localization test. With single gland disease, this study is accurate in identifying the abnormal gland 85-100 percent of the time. More recently, preoperative localization with technetium sestamibi has become a component of the minimal access radioguided neck exploration for primary hyperparathyroidism.

Treatment

Surgical exploration of the neck by experienced surgeons results in successful treatment (defined as permanent return to normal blood calcium levels) in 95 percent of patients. The current debate surrounding the extent of neck exploration necessary to achieve a successful outcome is being altered by rapid changes in technology.

Bilateral exploration to identify all parathyroid glands has been proposed as a result of earlier studies showing failure to control hypercalcemia because the abnormally functioning gland(s) were not identified and removed. Adenomas involving more than one gland or hyperplasia involving all parathyroid glands are the conditions which require exploration of both sides of the neck.

The combination of three technological advances: a highly accurate localization test (technetium sestamibi scan), the gamma probe (handheld Geiger counter), and the availability of an intraoperative parathyroid hormone assay has stimulated fundamental change in the surgical treatment of primary hyperparathyroidism. These new technologies allow the surgeon the possible option of a minimal access approach with a very short hospital stay.

By combining the three modern technologic advances, we have developed a flexible treatment approach to patients with primary hyperparathyroidism. Once the biochemical diagnosis of primary hyperparathyroidism is clearly established, all patients undergo technetium sestamibi scan which serves as selection criteria for minimally invasive radio-guided parathyroidectomy. This is highly accurate, if a single abnormally functioning parathyroid is the cause of the hyperparathyroidism. This localization test is not helpful if more than one gland is functioning abnormally.