Minimal Access Neck Surgery
One of the newest frontiers is in minimally invasive soft tissue surgery performed outside an established body cavity. The neck has been one of the soft tissue spaces of considerable interest, and endoscopic or endoscopic-assisted techniques have recently been used to perform both thyroidectomy and parathyroidectomy. Several technical advances have facilitated the development of these new procedures, including the availability of balloon dilator for making artificial space, external lifts, ultrasonic coagulators, and smaller 2 to 3 mm diameter endoscopic instrumentation.
Background
In whole world thyroidectomy and parathyroidectomy are the two most commonly performed endocrine surgical procedures. The most common indication for thyroidectomy is a solitary nodule that is not clearly benign on fine-needle biopsy. Parathyroidectomy is most commonly performed for primary hyperparathyroidism, in which a single enlarged gland or adenoma accounts for maximum number of cases. The principles of neck exploration for these two disorders are well established, and the morbidity of operation is low when carried out by an experienced minimal access surgeon. Unlike many open abdominal operations, recovery is also rapid and most patients are discharged from the hospital the day after surgery and return to unlimited physical activity within fortnight.
Already many surgeons are attempting to perform thyroidectomy and parathyroidectomy through smaller and smaller open incisions to achieve better cosmetic results. However, as open incisions become smaller, surgical exposure, access, ease of dissection, and even safety may be compromised. Further evidence is that parathyroidectomy, for example, is viewed as an invasive procedure by patients and by referring endocrinologists is the reluctance of many individuals with asymptomatic or minimally symptomatic disease to undergo a definitive and curative operation despite the cumulative risks of hyperparathyroidism over time, including osteoporosis and other metabolic sequelae.
In parathyroid surgery, there has also been interest in a focused, unilateral exploration of the neck rather than the accepted gold standard of bilateral neck exploration with identification and biopsy of all four parathyroids. Exploration of both sides of the neck avoids the problem of missed multiple adenomas or asymmetric hyperplasia, which can occur in up to 5 to 15 percent of cases and eliminates the need for preoperative localization studies. However, the advantages of unilateral neck exploration are that it results in less dissection, operative times are shorter. There may also be fewer injuries to the recurrent laryngeal nerve and the other parathyroid glands from leaving the contralateral neck undisturbed. Improvements in the accuracy of parathyroid imaging, such as 99mTc sestamibi scanning and intraoperative assessment of curative resection with the quick parathyroid hormone assay have led to better outcomes from and wider application of the unilateral approach. These considerations become increasingly important in the current economic environment in health care.
Under these circumstances, minimal access approach to neck exploration may offer certain possible benefits, including improved visualization due to magnification, better cosmesis, less trauma to the neck musculature, less pain, and a more rapid recovery. Disadvantages of this approach might include longer operative times, increased hospital costs, possible risk of injury to the recurrent laryngeal nerve, potential tumor spillage, inability to localize the parathyroids, and adverse effects of neck insufflation. Consideration of an endoscopic approach to neck exploration, at the least, presents several challenges from an anatomic standpoint. Unlike the abdominal cavity, in which there is an easily distensible space for laparoscopy, the area that must be expanded and maintained to allow endoscopic access in the neck is composed of only potential spaces between soft tissue and muscle planes and the trachea. The thyroid and parathyroid glands are situated within the pretracheal space and are covered by the strap muscles anteriorly and laterally, which also limits exposure and access.
The absence of a discrete anatomic compartmental boundary in the neck adds further problems if insufflation is used because of the potential for gaseous diffusion subcutaneously and into the mediastinum. The thyroid and parathyroids are also highly vascular structures and are intimately related to the recurrent laryngeal nerve and inferior thyroid artery. Further, the location of the parathyroids, especially the inferior glands, is often variable.
Several technologic advances have been necessary to facilitate the development of endoscopic neck exploration. Miniature 2 to 3 mm endoscopic instruments have been constructed suitable for smaller working space and the more delicate structures in the neck. Many balloon space maker devices have been invented, just like used in laparoscopic hernia repair, could be adapted to create a working space. Gasless laparoscopy has been used with mechanical lifts and retractors to maintain the working space and thus eliminate the need for insufflation of the neck. Ultrasonic coagulators and small clip appliers may be more appropriate for obtaining hemostasis in the neck rather than monopolar cautery. Endoscopic ultrasound also aid in intraoperative localization of the parathyroid adenoma, which is localized preoperatively by sestamibi scanning. These considerations led our group to first explore the possibility of an endoscopic approach to neck exploration in an experimental animal model.
Endoscopic Parathyroidectomy
Endoscopic parathyroidectomy in humans was first performed successfully by Gagner in 1995. The patient had familial hyperparathyroidism and initially presented with acute pancreatitis for which he required laparoscopic pancreaticojejunostomy with stone extraction as well as laparoscopic cholecystectomy. A preoperative sestamibi scan showed four-gland uptake consistent with generalized parathyroid hyperplasia, and a subtotal parathyroidectomy was performed endoscopically. Access to the neck was obtained with four 5 mm ports placed 1 cm above the clavicle and sternal notch. Exposure was achieved by insufflation of the subplatysmal space with 15 mm Hg2+ pressure, which was maintained throughout the operation. Operative time was 5 hours and intraoperatively the patient experienced tachycardia and hypercarbia. Postoperatively, he had subcutaneous emphysema from the eyelids to the scrotum. He recovered uneventfully, however, and was discharged on the fourth postoperative day with a normal serum calcium level.
Since this initial report, endoscopic parathyroidectomy has been carried out by a small number of surgeons using either low-level gas insufflation of the neck or external retractors without CO2 gas. Gagner has excised parathyroid adenomas in several cases, but uses a lower CO2 insufflation pressure (7 to 10 mm Hg2+ ) to reduce the adverse effects of this technique. Duluq has also successfully performed endoscopic parathyroidectomy in several patients with low-level (7 mm Hg2+ ) CO2 insulation for exposure. Norman and Albrink attempted parathyroidectomy in four patients after preoperative localization with sestamibi imaging. Initial access to the pretracheal space was achieved via a 1.5 cm incision, but CO2 at a low insulation pressure (8 mm Hg2+ ) was used to maintain a working space. Although the parathyroid adenoma was visualized in three of the four cases, endoscopic excision was successful in only two patients, and only one normal parathyroid was identified out of these four explorations. At the conclusion of the endoscopic procedure, all patients were converted to open exploration via a 3.5 cm incision, through which the ipsilateral remaining parathyroids, both normal and adenomatous, were identified and either biopsied or removed. Postoperatively, there was subcutaneous air in the anterior neck, but no other sequela of CO2 insulation were noted.
We recently performed endoscopic parathyroidectomy in two patients with primary hyperparathyroidism using a gasless technique. Preoperative localization of the parathyroid adenoma was carried out with 99mTc sestamibi scanning, which identified abnormal uptake in the left neck of both patients. Following the induction of general anesthesia, the parathyroid adenoma was more precisely localized with transcutaneous ultrasound and in each case was posterior to the thyroid lobe. A 1.5 cm incision was then made at the sternal notch, and the strap muscles were divided in the midline to enter the pretracheal space under direct vision. In the first patient, a modified space maker balloon was inserted into this space and inflated to 60 ml volume. After removal of the balloon, a working space was maintained with a handheld S-shaped retractor. The strap muscles were further separated from the left lobe of the thyroid and the thyroid was retracted medially with a Babcock clamp placed through the open insertion site. Endoscopic visualization was achieved with a 3 mm 30° arthroscope. Two 4 mm ports were placed in the neck anterior to the sternocleidomastoid muscle.
A normal inferior parathyroid was identified and biopsied, and the adenoma was localized to the superior position with the aid of laparoscopic ultrasound. The enlarged gland was posterior to the thyroid lobe and wedged between two branches of the inferior thyroid artery and the recurrent laryngeal nerve, which led to a lengthy and tedious dissection. Excision was accomplished by blunt dissection with 3 mm endoscopic instruments and the ultrasonic scalpel. Small ligaclips placed through the open insertion site were used to ligate the vascular pedicle. The second patient was approached in a similar fashion, but a small lift ring attached to a mechanical retractor was used to maintain exposure. A left superior adenoma was removed that weighed 1.7 g. The recurrent laryngeal nerve and inferior thyroid artery were identified during the dissection, but it is difficult to locate the inferior parathyroid despite careful examination of the region of the thyrothymic ligament. Total operative time in our two patients has averaged approximately 4 hours. Exposure was suboptimal at times due to the small space, and there was difficulty in retracting the strap muscles laterally and the thyroid gland medially. Very small amounts of bleeding or fluid accumulation obscured the operative field and required frequent sponging through the open insertion site. Manipulation and retraction of the parathyroid with the small instruments was sometimes difficult as well. Parathyroid tissue was confirmed in all specimens and serum calcium levels have been normal postoperatively.
Miccoli used an endoscopic-assisted approach in approximately 20 patients. Handheld retractors are used to maintain exposure, and the dissection has been carried out with one or two lateral ports. A brief period of insufflation is used initially to aid in expanding the pretracheal space, but the remainder of the operation is carried out, with gasless retraction. Preliminary results have been favorable, but not all patients have had a normal ipsilateral parathyroid identified. Confirmation of successful excision of the parathyroid adenoma was made intraoperatively with use of the quick parathyroid hormone assay.
Alternatives to Endoscopic Parathyroidectomy
Minimally invasive or less invasive approaches to parathyroidectomy have been described recently that do not require endoscopic techniques or instrumentation. Norman and Chheda performed parathyroidectomy through a minimal 2 to 3 cm open incision after precise preoperative localization of the adenoma with sestamibi imaging. The technique used for parathyroid localization is analogous to that used for sentinel node mapping with radiolymphoscintigraphy. The 99mTc sestamibi scanning is carried out 3 hours prior to surgical exploration. The operation is then directed with an 11 mm Neoprobe, which is used to scan and quantitate radioactivity in all four quadrants of the neck. A 2 to 3 cm incision is made over the site of maximal gamma activity, and the adenoma is excised through this minimal incision. The authors have used this technique in 14 patients, 13 of whom had adenomas and one who was correctly predicted to have parathyroid hyperplasia. The adenomas were located operatively on average in just 19 minutes. Nine cases were carried out under local anesthesia, and 11 (79%) patients were discharged the same day as surgery. Serum calcium levels were normal postoperatively and there were no operative complications. This approach is potentially very attractive because it requires minimal dissection and can be carried out under local anesthesia as strictly as outpatient procedure. Both operative and recovery times should be short, which may result in lower hospital costs despite the use of preoperative scintigraphic localization. Frozen section examination by pathology may also become unnecessary if, after excision, all radioactivity is confined to the resected specimen. The limitations of this approach currently are that neither the ipsilateral parathyroid nor the recurrent laryngeal nerves have been routinely identified in these dissections. Further, the accuracy of “sentinel” mapping of the parathyroid adenoma must be confirmed by other investigators.
Thoracoscopic Parathyroidectomy
Video-assisted thoracoscopy should be considered as an alternative to median sternotomy in patients with ectopic mediastinal parathyroid adenomas. Prim and coworkers reported the use of thoracoscopic techniques to successfully excise mediastinal parathyroids in four patients with persistent hyperparathyroidism after failed cervical exploration. All glands were localized preoperatively by a combination of radionuclide scintigraphy and CT scan. The location of the abnormal glands in these four cases included the aortopulmonary window, near the ascending aorta, the aortic arch, and the region of the main pulmonary artery. Three thoracoscopic ports were used, including a 10 mm initial access port placed in the midaxillary line at the sixth intercostal space. Operative times averaged 3.25 hours and all patients became normocalcemic postoperatively, although one patient with secondary hyperparathyroidism developed recurrent hypercalcemia 9 months after surgery. A subxiphoid laparoscopic approach has also been used to excise a mediastinal parathyroid adenoma , but this technique would appear to provide access to glands in the anterior mediastinum only.
Endoscopic Thyroidectomy
Endoscopic excision of the thyroid is more technically demanding because of the more complex blood supply and the intimate relationship of the thyroid gland to the recurrent laryngeal nerve. A lateral approach is used in which three laparoscopic trocars are placed in the subplatysmal space along the anterior border of the sternocleidomastoid muscle from the jugular notch to the angle of the mandible. Both low pressure CO2 and a wall lifter inserted at the jugular trocar site are used to maintain a working space. Division of the strap muscles is necessary to access the thyroid. The thy-roid vessels are divided with clips, and an ultrasonic dissector is used to dissect the thyroid from the recurrent laryngeal nerve. In addition, both parathyroids are identified and preserved, as is the external branch of the superior laryngeal nerve.
Conclusion
Early experience with endoscopic neck exploration prevents any definitive conclusions about its role in the management of patients with either hyperparathyroidism or thyroid disorders. Published experiences have to date been limited to small case reports, and results and outcomes have not been reported in detail. The minimally invasive open approach of “sentinel” parathyroidectomy reported by Norman and Chheda has much to commend it, including accurate localization, rapid operative times, and improved cosmesis, and it is an outpatient operation that can be performed under local anesthesia.
Although the laparoscope provides optical magnification of important neurovascular structures, including the recurrent laryngeal nerve, better methods for exposure and retraction of the strap muscles and thyroid would greatly facilitate visualization and dissection. Improved instruments are needed that allow safe manipulation of the parathyroid to lower the risk of parathyroid rupture as well as to speed the operative dissection. Suction and irrigation devices designed specifically for small spaces such as the neck would help maintain a dry operative field. Surgeons will also need flexibility in the exposure and operative approach to deal successfully with variations in parathyroid anatomy.
Patient selection should be careful for endoscopic approach until there is further experience and improved operative technique. Individuals, who are obese, have a nodular goiter, have had previous neck surgery, or who are likely to have generalized parathyroid hyperplasia should not be considered as a good candidate for an endoscopic exploration. Despite these limitations and challenges, the search for less invasive means for performing neck exploration will undoubtedly continue, and has already led to renewed interest in a unilateral operative approach in patients with primary hyperparathyroidism.
