The Surgical Experience
Surgical treatment of hyperparathyroidism is challenging and should be performed by an experienced endocrine surgeon. Intraoperative PTH testing and the gamma probe are used in all of our parathyroid operations. The entire operation from start to finish takes 60-90 minutes. A general anesthesia is used most often but a local anesthesia with sedation through an IV is an option for some people. Your surgeon’s and your anesthesiologist’s experience and comfort, medical conditions that you may have (such as acid reflux, sleep, apnea, and claustrophobia), and your wishes determine which type of anesthesia will be used.
Local or Regional Block Anesthesia
This is a form of local anesthesia (“numbing” medicine). This is usually done with a combination of Lidocaine (short acting) and Marcaine (long acting) local anesthetics. The medicines are injected into the side of the neck along the muscle that extends from your jaw to your breastbone. This medication will numb the tissues in this region. You will feel touching and pressure, but you should not feel sharp pain. Usually this works very well, but sometimes additional medication needs to be injected in the area of the incision. A sheet or blanket will need to be covering your upper neck and face which can make some people uncomfortable, therefore many times this form of anesthesia is accompanied by some intravenous sedation.
Intravenous (IV) Sedation or “Conscious” Sedation
Sedation can be used to supplement local or regional block anesthesia. Sedation can be very light (just enough to help you relax) or heavy (where you are in a fairly deep sleep). Sedation is usually performed by giving medications through an IV catheter that is in your arm. The medications can help minimize pain and discomfort, and can also make you sleepy and forgetful. You will not have a breathing tube in with this form of anesthesia so it is important for you to remain awake enough that you continue to breathe comfortably on your own. You may be awake enough to talk and move during surgery, but it is not uncommon for you to not remember the events that occurred while under sedation. Some patients have medical conditions that make this form of anesthesia not a good option. This form of anesthesia can be associated with some mild nausea, which is usually easily treated. There is also the risk that you could be made too sleepy and stop breathing on your own, therefore it is essential that you have an anesthesiologist that is experienced in giving sedation.
General anesthesia is the administration of either IV or inhaled medications which put you into a deep sleep. Since medications are often given to stop your muscles from working temporarily, an endotracheal tube (breathing tube) or an LMA (laryngeal masked airway) is used. An LMA involves placing a special tube with a cuff in the back of your throat which allows the anesthesiologist to help you breathe if it is needed. Most patients tolerate general anesthesia very well and it is considered very safe. The most common side effect is a mild sore throat and some nausea. There are many medications that can be given to help prevent or reduce the nausea.
How is parathyroid surgery performed?
Parathyroid surgery has traditionally been performed using a bilateral neck exploration. This technique has been proven over time to be very safe and effective when performed by an experienced surgeon. This operation involves identifying all four parathyroid glands but removing only those that are abnormal. Since 80-85% of patients with primary hyperparathyroidism have only one gland that is abnormal, many surgeons have shifted to doing a more limited or focused exploration in patients thought to have a high likelihood of having a single abnormal gland. This more focused approach, which is performed in more than 80% of our patients at the University of Wisconsin, is often referred to as a “minimally invasive parathyroidectomy” or “MIP”.
Minimally Invasive Parathyroidectomy
(May be referred to as MIP, minimally invasive radioguided parathyroidectomy, MIRP, focused parathyroidectomy, targeted approach, video assisted)
Minimally invasive parathyroidectomy (MIP) consists of identifying a single abnormal gland and removing it without the identification of the remaining normal parathyroid glands. MIP is typically performed through a smaller incision than the bilateral exploration, usually 1-3 cm. MIP consists not just of one procedure, but a variety of techniques that can be used either alone or in combination. A central component of each of these techniques is accurate pre-operative localization. A second component, is intraoperative PTH testing. Other adjuncts such as radio-guidance, and local anesthesia may also be used.
The cure rate of MIP appears to be equal to conventional exploration1-3. There are several potential advantages of MIP over a bilateral neck exploration including: smaller incision, improved cosmesis, shorter operative time, creation of less scar tissue, and fewer problems with low calcium levels after surgery. The incidence of symptomatic low calcium levels has been shown to be reduced from 25% in a bilateral exploration to 7% with MIP 1. The ability to perform a MIP under local anesthesia, if desired, is another advantage. MIP has been shown to reduce operating room time by up to 50% and many patients are able to have their surgery done as an outpatient.
Prior to being considered for a MIP, a patient must have undergone pre-operative localization that reveals a single abnormal gland. An additional peripheral IV is often placed to be used for intraoperative PTH testing. Prior to making an incision a baseline PTH level is drawn from either from a peripheral IV line or a vein in your neck. Minimally Invasive parathyroidectomy can be performed through either a medial or lateral approach.
Intraoperative PTH Testing
While the majority of patients with primary hyperparathyroidism have a single abnormal gland, up to 20% of patients will have either multiple adenomas or hyperplasia of all four glands. Pre-operative imaging is not very good at identifying when patients have multiple abnormal glands. Therefore, when all of the parathyroid glands are not identified during surgery (as in a minimally invasive parathyroidectomy) it is important to have a method other than visual inspection to confirm that all of the abnormal glands have been removed. Parathyroid hormone (PTH), which is produced by the parathyroid glands, is cleared from the blood stream very quickly (within a few minutes). Hence within 5-10 minutes of removing an abnormal gland over half of the PTH in the bloodstream will have been cleared. By testing PTH levels pre-operatively and then again after removal of the abnormal gland you can determine if there are additional hyperfunctioning glands present. Dr. Chen and Dr. Sippel look for at least a 50% drop in the PTH in order to consider the patient cured. If the PTH levels do not drop by 50% then they know that there is additional abnormal tissue and will proceed to identify the other glands to ensure that all abnormal glands are removed (4). PTH levels are typically drawn at the beginning of your operation and 5, 10, and 15 minutes after the abnormal gland is removed. It can take anywhere between 10-40 minutes to get the results back from the PTH testing. You are kept in the operating room while you surgeon waits for the results. The goal is to not end the operation until they have confirmation that you are cured of your hyperparathyroidism.
(Minimally Invasive Radioguided Parathyroidectomy, MIRP)
Radioguided parathyroidectomy involves giving a small injection of Tc-99m sestamibi (the same agent used for the sestamibi scan, just a smaller dose) the morning of surgery. This radioactivity concentrates in the parathyroid glands allowing you to use a gamma probe to identify them during surgery. A gamma probe can be used intraoperatively to guide incision placement as well as to direct the dissection, allowing the surgeon to focus in on the location of the abnormal parathyroid tissue. The gamma probe is also used to confirm that the tissue resected is indeed parathyroid tissue. Radioactivity > 20 % of the background is considered diagnostic for parathyroid tissue (5).
The benefits of the intraoperative gamma probe have been debated. The greatest benefit appears to be in reducing operative time when it is a reoperation, the parathyroid adenoma is located in an ectopic position, or when the sestamibi scan has a false positive due to a thyroid nodule. In these cases, the radioprobe can direct the intraoperative exploration to the location of the abnormal gland.
(May be referred to as open parathyroidectomy, standard parathyroidectomy, 4 gland exploration, conventional parathyroidectomy)
Bilateral exploration is the traditional surgical approach to hyperparathyroidism. This approach has proven over time to be highly successful with cure rates of 95% when performed by an experienced surgeon. In order to be successful, the surgeon must identify all four parathyroid glands. This requires expertise in the recognition of the parathyroid glands in both their normal and unusual locations. In the past each parathyroid gland was biopsied to confirm that all glands were identified. However, due to the risk of injuring the blood supply to the parathyroid glands, biopsies of normal appearing glands is no longer recommended. Pre-operative localization and special intraoperative adjuncts (such as intraoperative PTH testing or radioguidance) are not required, but are often used to guide the surgeon.
Traditionally a bilateral exploration was performed through a 5-7 inch incision. Dr. Chen and Dr. Sippel are able to do this operation through a much smaller 1½-2 inch incision. The incision is usually located in the middle to lower portion of the neck and is curved to match the skin folds in your neck. Experienced surgeons understand the variations in anatomy that can exist and are very successful at finding parathyroids, even when they are not in their normal location. Parathyroids can be located behind the esophagus, in the upper chest, or even inside of the thyroid gland. The goal of the first operation is to cure the patient of their hyperparathyroidism. Since multiple abnormal parathyroid glands are found in 15- 20% of patients, it is essential to make every effort to identify all four parathyroid glands. If only a single abnormal gland is identified, then it should be resected. If all four glands are abnormal then the treatment options are a subtotal parathyroidectomy (removal of 3 ½ glands) or a total parathyroidectomy (removal of all parathyroid tissue) with autotransplantation of part of a parathyroid to the forearm. An autotransplant involves placing several small pieces of parathyroid tissue into a muscle either in the neck of the arm. It will grow a new blood supply and will typically start functioning in 4-6 weeks.
What is parathyroid autotransplantation?
Parathyroid autotransplantation involves taking parathyroid tissue (either normal or abnormal) and taking it from its normal location and placing it into a muscle bed either in the side of the neck or in the forearm. The parathyroid tissue is usually cut into 1-2 mm fragments and is placed in small pockets within the muscle. While the gland does not function immediately, it will develop a new blood supply and will typically start working within 4-6 weeks. If all of your parathyroid tissue has been removed and you are relying on an autotransplant for you parathyroid function you will need to take both calcium and calcitriol ( activated Vitamin D) until your autotransplant starts functioning.
Autotransplantation is usually only done in conjunction with a total parathyroidectomy (removal of all parathyroid tissue). This procedure is performed when all of the parathyroid glands are abnormal, usually in the setting of familial disease. Since all of the glands are abnormal they are all removed from the neck to prevent a recurrence and/or the need for a reoperation in the neck. Since everyone needs some parathyroid tissue, the autotransplant can start functioning (produce parathyroid hormone) to minimize patient symptoms and allow most patients to stop supplemental calcium and calcitriol. In cases where the autotransplant is using abnormal parathyroid tissue, it is usually placed in the arm so that it can be easily accessed in the future if it were to grow and overfunction. If some of the tissue has to be removed in the future this can be done very safely under local anesthesia without the risks of reoperating in the neck.
Parathyroid Cancer and Cryopreservation
Most enlarged parathyroid glands are just benign (non-cancerous) growths. In <1% of cases the abnormal parathyroid gland is actually a cancer. While occasionally a biopsy may be performed in the operating room to confirm the presence of cancer, this is rarely done and in most cases the diagnosis of cancer is based on the outside appearance of the tumor, not its microscopic findings, when parathyroid tissue is removed during surgery it is usually sent to the pathologist for a diagnosis. Almost always they find benign parathyroid tissue. Results from pathology may take from 2- 10 days to receive after surgery. Occasionally your surgeon may decide to cryopreserve your parathyroid glands instead of sending them to the pathologist for a diagnosis. Cryopreservation involves freezing the tissue in liquid nitrogen. These cryopreserved glands can then be defrosted in the future and autotransplanted if needed.