Minimally Invasive Surgery of the Thyroid Treatment & Management

Minimally invasive open thyroidectomy (MIT) is similar to conventional thyroidectomy in its surgical approach. The major difference is the length of the neck incision. A smaller incision improves cosmesis and reduces discomfort. Typically, a skin incision less than 6 cm is considered minimally invasive. The remainder of the procedure is exactly the same as is used in conventional thyroidectomy. Adaptations to this technique include transection rather than lateral retraction of the strap muscles (the Sofferman technique). ^[1]

Minimally invasive video-assisted thyroidectomy (MIVAT) typically involves a skin incision no greater than 3 cm that is placed slightly higher than the conventional thyroidectomy incision. Open dissection is carried out until the superior thyroid pole is encountered, after which the endoscopic video-assisted techniques are used.

Totally endoscopic techniques that include an axillary approach and the use of gas insufflation have been described, but these have not gained widespread use. Recent evidence suggests that the use of robotic technology may enhance the effectiveness of endoscopic techniques; however, these data are very preliminary. ^[13]

Videos of minimally invasive thyroidectomy for papillary carcinoma are included below.

First and foremost, the patient should meet the criteria for candidacy for MIVAT approach.

Preoperative laboratory studies should include baseline serum electrolyte levels, CBC count, coagulation panel, and pregnancy testing, if applicable.

A chest radiograph and electrocardiography should be performed as necessary.

When obtaining consent for MIVAT surgery, the possible need to convert to open, conventional thyroidectomy should always be discussed with the patient.

The standard thyroidectomy or neck dissection set up is supplemented with a set of Miccoli instruments specially designed for MIVAT (see the first image below). A 5-mm, 29-cm long, 30° endoscope is ideal for endoscopic visualization. Harmonic scalpel scissors (Ethicon Endo-Surgery, Inc., Cincinnati, Ohio) are then used to ligate and divide the blood vessels (see the second image below).

The patient is placed in the supine position with slight neck extension (see the first image below). The neck is then prepared and draped with sterile technique. A horizontal incision is placed parallel to relaxed skin tension lines that are 3 cm or less in length (see second and third images below). The incision is placed between the sternal notch and cricoid cartilage, usually less than 1 cm inferior to the cricoid. ^[10]

Cautery is used to dissect the subcutaneous tissues until the midline raphe of the strap muscles is identified. The raphe is separated superiorly and inferiorly for a distance of about 3 cm. Anterior jugular veins can be preserved in most cases. Gentle and blunt dissection with peanuts is used to separate straps from the thyroid gland and displace them laterally. The middle thyroid vein or other vessels that are encountered at this time are clipped and divided.

Miccoli retractors are used to retract the strap muscles and soft tissues and expose the superior lobe and vascular bundle. At this point, a 30°, 5-7 mm rigid endoscope is introduced into the field to visualize the superior pole (see the image below). Three persons are required for the procedure at this point: a surgeon, a retractor, and an endoscopist.

The surgeon uses Miccoli spatula-shaped dissectors and aspirator dissectors to dissect the superior pole vascular bundle. Care is taken to identify and preserve the external branch of superior laryngeal nerve, which is identified medial to the superior vascular pedicle. The thyroid lobe is then retracted medially and endoscopic dissection is carried further to dissect the lateral and posterior attachments. The recurrent laryngeal nerve (RLN) is identified and preserved during this step, along with the parathyroid glands (see the image below).

Once the lobe has been sufficiently mobilized, an atraumatic clamp can be used to externalize the lobe from the incision, and the remainder of the dissection can be carried out under direct vision. The isthmus is divided, and the lobectomy is complete. Total thyroidectomy is performed by repeating the same procedure contralaterally.

The wound is irrigated and complete hemostasis is ensured. The strap muscles are reapproximated. The skin is closed in layers with absorbable sutures and skin sealant. No external drainage is required.

Postoperatively, the patient should be given analgesics, antiemetics, and postoperative antibiotic prophylaxis. Any preoperative thyroid hormone supplementation should be continued.

A prospective, double-blind, randomized trial by Hong et al found repeated administration of acetaminophen 1 g IV over the initial 24 hours following thyroidectomy was easy, effective, safe, and well tolerated for pain management in patients with moderate-to-severe postoperative pain. The IV route for acetaminophen is currently investigational in the United States. ^[14]

For total thyroidectomy, ionized calcium and albumin levels should be checked in the recovery room and every 6-8 hours thereafter. Typically, hypocalcemia is defined as a corrected serum calcium level below 8.0 mg/dL. Early signs of hypocalcemia include perioral numbness or paresthesia and the Chvostek sign (facial spasm upon percussion of the facial nerve). Calcium supplementation may be required in some cases.

Some groups consider patients who undergo MIVAT lobectomy for same-day discharge with close follow-up.

The patient is seen in the office 1-2 weeks postoperatively (see the first image below), and again 6 weeks later (see the second image below). The wound healing should be assessed, and any pathology results and further treatment plans should be discussed. If the patient experiences hoarseness or shortness of breath, vocal fold movement should be assessed.

Complications from minimally invasive video-assisted thyroidectomy (MIVAT) are the same as with conventional thyroidectomy and occur at a similar rate. However, one study suggests surgical site infections are significantly less with the endoscopic technique. ^[15] Complications include the following:

• Bleeding or hematoma

• Wound infection

• Transient or permanent recurrent laryngeal nerve (RLN) injury

• Transient or permanent external branch of the superior laryngeal nerve (EBSLN) injury

• Hypocalcemia

Cosmetic outcome is much better (see the images below) than that of conventional thyroidectomy. Some series have shown less postoperative pain and discomfort after minimally invasive video-assisted thyroidectomy (MIVAT) than with conventional thyroidectomy. ^[16] The MIVAT approach has also resulted in shorter hospital stays. ^[11] In groups with the most experience performing MIVAT, operative time is equivalent to that of conventional thyroidectomy, but a learning curve certainly exists.

For early papillary thyroid carcinoma (PTC), the oncologic adequacy of MIVAT is comparable with that of conventional thyroidectomy.

Around 15-20% of thyroid nodules that require surgery fit within the size criteria for minimally invasive video-assisted thyroidectomy (MIVAT). MIVAT surgery will likely gain an increasing role in this subsection of thyroid nodules.

Because MIVAT surgery is still relatively new, the following controversies exist:

Size criteria

Most groups advocate for a nodule diameter that is less than 30 mm and a thyroid volume below 30 mL. Some authors have shown that they can safely operate on a nodule size up to 40 mm in diameter and a thyroid volume approaching 50 mL.

Eligibility

Patients with a history of thyroiditis are still excluded from candidacy for MIVAT by certain groups. Some groups now include patients with Graves disease who meet size criteria, and also patients who require prophylactic thyroidectomy for RET germline mutation with normal calcitonin levels and no evidence of medullary thyroid carcinoma (MTC).

Oncologic adequacy

Excessive manipulation of the thyroid and removal of the specimen through a small incision may increase the risk of thyroid capsule rupture and the possible spillage of malignant cells. This has been disproved in at least one study. ^[6] The adequacy of MIVAT for resection of small, low-grade parathyroid carcinoma (PTC) is also considered controversial.

External drainage

MIVAT is usually performed without external drainage. Most conventional thyroidectomy is performed with external drainage.

Outpatient surgery

The safety of MIVAT as a same-day procedure is still being studied.