Medical Device Daily Contributing Writer
Endocrine surgeon James Norman, MD, performed a minimally invasive radioguided parathyroid (MIRP) surgery during a live web cast from Tampa General Hospital (Tampa, Florida) last month, done to remove a tumor of the parathyroid gland.
Norman is one of the world’s foremost experts on parathyroid disease. He developed MIRP in the mid-1990s and has since treated thousands of patients with parathyroid and thyroid tumors.
The technique uses intraoperative nuclear mapping – a method that allows virtually all parathyroid operations to be performed through a 1-inch incision. On average, the procedure takes less than 16 minutes. Parathyroid disease is non-cancerous. It is a hormonal disease.
Normally there are four parathyroid glands in the neck. They are found two to each side and an inch or so deeper than the thyroid gland. The sole purpose of the parathyroid glands is to control calcium within the blood in a very tight range. In doing so, parathyroid glands also control how much calcium is in the bones and therefore how strong and dense the bones are.
Although the parathyroid glands are intimately related to the thyroid gland anatomically, they have no related function. The thyroid gland regulates the body’s metabolism and has no effect on calcium levels, while parathyroid glands regulate calcium levels and have no effect on metabolism.
When diseased, the parathyroid gland excretes a hormone causing blood calcium levels to rise. High levels of calcium can cause people to feel run down, cause them to sleep poorly, make them more irritable than usual and even cause a decrease in memory. Even though half of patients with hyperparathyroidism (parathyroid disease) will state that they feel just fine, after a successful parathyroid operation and removal of the diseased gland, more than 85% of these patients will claim to “feel much better.” Some say it’s like “someone turned the lights on.”
During the MIRP procedure, intraoperative mapping allows the assessment of the physiologic activity of individual parathyroid glands in real-time, thus negating the need for frozen section in 95% of cases and hormone assays in 100% of cases. These techniques, along with Norman’s experience, provide a cure rate of more than 99%.
During an MIRP procedure the four parathyroid glands are located and the diseased gland (usually only one) is removed. The objective is first to locate all four glands, then determine which one is making too much parathyroid hormone, then surgically approach and remove the appropriate gland and finally to assure the removed gland was the diseased one.
The patient in the webcast procedure was a 55-year-old woman who had flown to Tampa from California. Her symptoms matched those of parathyroid disease, even through two diagnostic scans done by her local physician had not shown abnormal activity. Pre-operative scans at Tampa General revealed an abnormally active gland.
The scan is the first step in Norman’s MIRP technique. The overactive parathyroid gland is made radioactive so it can be differentiated from all other structures in the neck. Key to success of this technique was the development of the Sestamibi scan in the early 1990s, which makes only parathyroid tumors radioactive for about three to four hours. During her scan, the patient was given a very small dose of the same drug that is used to examine the heart during heart stress tests. Then the abnormal gland could be seen on X-ray.
In the operating room, the patient was anesthetized, prepped and draped in the usual manner. Only her neck was visible to the surgeon. A marking pen was used to outline the 3/4-inch planned incision. Norman then tested the location of the diseased parathyroid using a radiation-detecting probe from U.S. Surgical (Norwalk, Connecticut). As the probe passed over the location of the targeted gland, a Geiger counter-like sound was heard.
Norman dissected down about an inch, located the thyroid gland and then the targeted parathyroid – the lower one on the patient’s right. Again, the probe was used to assure radioactivity of that gland. Norman then isolated the one artery and vein to the gland and clipped them with a titanium clip. The overactive parathyroid was about the size of a large black olive – fairly typical, Norman said. A normal parathyroid gland is about the size of a pea.
Norman moved the dissected gland away from the patient and again checked its radioactivity, which continued high. Moving the probe back to the patient, no radioactivity was signaled. No frozen section or blood hormone tests were done. The wound was closed in a typical manner and a small impervious bandage was placed over the incision.
The patient was expected to be discharged within two hours. Norman commented, “Of all our 2,000 consecutive patients, they all went home within two hours of the operation.”
As the patient was being moved to recovery, Norman answered questions e-mailed during the case. One questioner asked, “Is there a time the patient must be quarantined because of the radioactive materials?” Norman said “no,” adding: “the radioactive materials we use are very benign. As you can see, I stand right next to the patient. I am constantly measured for radioactivity changes. This is a non-event.”
Another e-mailed question asked: “Do patients with this disease always have elevated calcium levels?” “Class-ically, yes,” said Norman, “but not always. Patients with highly functional kidneys can have normal blood calcium levels but often form kidney stones because of the calcium. This happens in about 5% of patients.”