A number of surgical procedures and surgical approaches have been developed and the terminology can be confusing. Aside from fine needle or core needle aspiration of the thyroid gland, the minimal operation for management of the thyroid is hemithyroidectomy, or thyroid lobectomy. This consists of removal of one lobe of the thyroid gland, and the isthmus of the gland. The opposite lobe is not removed, and in general the remaining thyroid gland will produce enough thyroid hormone for the body. Indications for this procedure include unilateral goiter and unilateral benign thyroid nodules. This procedure may also be appropriate for small, non-aggressive thyroid carcinomas less than 1cm.
Total thyroidectomy (sometimes called near-total thyroidectomy) is the surgical removal of the entire thyroid gland. Indications for removal of the gland include most types of thyroid cancer, large goiters causing compression of the airway, and Grave’s disease.
In addition to classifying the extent of surgical resection, a number of surgical approaches have been described. Classically, standard thyroid lobectomy or thyroidectomy has been performed through an incision low in the neck called the low collar incision. The size of the incision is dictated by surgeon preference and need for adequate exposure to remove the tumor. Classically 8-12 cm (3-5 inch) incisions were performed.
Most thyroid nodules are small, and performing a full collar incision is not necessary to provide needed surgical exposure to safely remove the thyroid lobe. Patient concern about cosmetic appearance has led surgeons to explore performing surgery through smaller incisions to extract tumors.
Minimally invasive thyroidectomy is a surgical approach to remove the thyroid gland through smaller incisions. There is no clear definition of what “minimally invasive” means, and surgical incisions as large as 6 cm. have been classified as “minimally invasive”. Incisions as small as 1 inch (2.5 cm) can be performed for patients with favorable neck anatomy and small tumors.
Another variation of the minimally invasive thyroidectomy is the minimally invasive video-assisted thyroid surgery (MIVAT). MIVAT combines the small incision with use of endoscopes to help provide illumination and visualization of the tumor. This technique can be performed on incisions as small as 2.0 cm (0.8 inches), and generally has excellent healing and cosmetic result. The operation is longer, requires the surgeon operate off a video monitor, and requires assistants to retract the tissues and another assistant to hold the endoscope.
The most recent trend has been to perform thyroid surgery while avoiding any neck incision at all. Transaxillary robotic thyroid lobectomy and transaxillary robotic thyroidectomy were developed in Korea, and over the last several years has been utilized by a small but growing number of surgeons. UC Irvine was the first institution on the West Coast of the United States to perform this operation. In this operation, an incision is made in the axilla (armpit) and dissection is carried superiorly across the collar bone into the neck. The muscles around the thyroid gland are retracted to expose the thyroid gland. A special retractor is placed to create a space for the surgeon to remove the thyroid gland. Next, an endoscope with two cameras that produce three-dimensional viewing is inserted into the incision, and three robotic arms are inserted into the incision. The primary surgeon performs surgery by manipulating the instruments in the robotic arms from a console adjacent to the patient, and a bedside surgical assistant can change instruments on the robotic arms, and perform additional tasks to support the primary surgeon. The surgeon has excellent magnified visualization, can manipulate the camera to customize the view of the field, and works with surgical instruments that are more maneuverable than the human wrist and hand. The system also has tremor filtration and scaling of movements to eliminate tremor and allow very fine microsurgical movements if needed.
The primary advantage of this surgical procedure is avoidance of an incision on the neck. For patients who develop hypertrophic scars, those who develop keloids and persons who want to do everything possible to avoid an incision on the neck, this procedure is possible. There are a number of factors that affect suitability for this procedure. The procedure is not indicated for aggressive thyroid cancers, for very large tumors, or tumors with significant inflammation such as severe Hashimoto’s thyroiditis, Grave’s disease, or in patients who are significantly obese or have abnormalities of shoulder function.
In addition to the complications of standard thyroid surgeries listed below, there are several complications specific to this operation. Temporary numbness of the anterior chest is very common after this operation, and can last for several months. Rarely, nerve injury to the arm can occur, resulting in impaired arm and/or hand function. All cases of this complication reported to date have been temporarily, and is related to compression of the brachial plexus from arm positioning during surgery. For persons with pre-existing shoulder abnormalities, these could be exacerbated by surgery.
Thyroid cancer often spreads to lymph nodes in the neck. The first lymph nodes to be involved are generally the paratracheal lymph nodes. The nodes may be referred to as level 6 lymph nodes based on the AJCC staging criteria. The paratracheal lymph nodes are divided into pretracheal, prelaryngeal, and right and left lateral paratracheal lymph nodes.
Thyroid cancer can also spread to the lateral neck. When present, surgical removal is generally indicated. In the past, piecemeal or “berry picking” operations have been advocated, but currently, removal of all lymph nodes in all levels or compartments containing metastatic nodes is performed. For images of a functional neck dissection, see following images.
Risks of the thyroid surgery include the risks common to all surgeries including risks associated with administration of general anesthesia, bleeding, and infection. Poor cosmetic result from scarring of the neck or axillary incision may occur and require secondary scar management. Because the thyroid gland is situated directly in front of the trachea, or windpipe, airway obstruction may occur if blood collects in the area after surgery. For this purpose, a drain is often left in place for one to several days after surgery to help evacuate any blood in the area. Because there is no more gland to produce thyroid hormone after a total thyroidectomy, patients are dependent on long-term thyroid hormone supplementation after surgery. The two other complications that may occur after thyroid surgery involve two of the structures that are intimately associated with the thyroid gland and that may be affected by surgery, the parathyroid glands and the recurrent laryngeal nerve.
The recurrent laryngeal nerve provides nerve input to the vocal cords, and is also intimately involved with the thyroid gland. Great efforts are made during surgery to identify and preserve this nerve on both side of the thyroid gland. However, the risk of damage to this nerve must be understood prior to surgery. Permanent nerve damage occurs in approximately 1% of cases performed by a skilled surgeon. Temporary nerve damage occurs in 6-8% of cases. If the recurrent laryngeal nerve is damaged, patients may have vocal cord weakness or paralysis, causing either hoarseness or a weak, breathy voice, and in severe cases of bilateral paralysis, respiratory distress
The parathyroid glands control calcium homeostasis within the body. Because these structures are intimately associated with the thyroid gland, your calcium levels may be affected either temporarily or permanently after thyroid surgery. The rate of permanently low calcium levels after a total thyroidectomy is anywhere from 1-5%. Temporarily lowered calcium levels occur in approximately 15-40% of patients, and is treatable with calcium and vitamin D supplementation post-operatively.