Robot-Assisted Thoracoscopic Mediastinal Parathyroidectomy: A Single Surgeon Case Series

Introduction

Primary hyperparathyroidism caused by parathyroid adenoma is successfully treated in 96%–98% of cases with cervical parathyroidectomy at high volume centers. ¹ Postoperative persistent hyperparathyroidism is commonly caused by ectopic parathyroid tissue. ² Parathyroid adenomas are found in ectopic locations in 9%–20% of patients, and mediastinal parathyroid adenomas have been associated with larger gland size, higher serum calcium levels, and increased frequency of bone disease.^3–5

Since the cervical approach does not consistently provide adequate access to the mediastinum, sternotomy or thoracotomy was the preferred approach for surgical excision of a parathyroid adenoma located in the mediastinum before the introduction of minimally invasive thoracic surgery. ⁶

Minimally invasive techniques have been associated with decreased patient morbidity, shorter hospital stays, and improved cosmesis. In 1994 the first video-assisted thoracoscopic surgery (VATS) resection of a mediastinal parathyroid adenoma was performed by Prinz et al. ⁷ and proved to be a safe alternative to sternotomy.

In 2004 Profanter et al. performed the first robot-assisted thoracoscopic resection of a mediastinal parathyroid adenoma. ⁸ The robotic surgical platform offers three-dimensional vision, articulated instrument tips, and tremor filtering, each of which allows robot-assisted surgery to overcome some of the limitations of VATS. ⁹ Since Profanter et al. described their robot-assisted technique in 2004, there have been multiple case reports and small case series^10–21 but no large case series describing robot-assisted mediastinal parathyroidectomy. Herein, we describe the largest cohort of patients (n = 8) who underwent robot-assisted mediastinal parathyroidectomy, which has been our approach since 2013.

Materials and Methods

An institutional review board (IRB) approved retrospective review of eight consecutive single-surgeon, single-institution robot-assisted mediastinal parathyroidectomies performed between April 2013 and March 2018 was completed. No patients who underwent the procedure during this time period were excluded. Preoperative medical records and imaging, operative reports, histopathologic findings, and postoperative notes were reviewed. All patient data were kept in a secure database.

Results

Seven of the eight patients were female (Table 1). The patients' ages ranged from 28 to 69, body mass index (BMI) ranged from 24.8 to 42.9 (average BMI: 33.6), and seven of the eight patients had a preoperative diagnosis of primary hyperparathyroidism. Two patients underwent prior procedures for primary hyperparathyroidism: one complete neck dissection and one neck exploration with parathyroidectomy. Preoperative serum calcium ranged from 10.2 to 12.1, and PTH ranged from 70 to 260. The additional patient had a preoperative diagnosis of thymoma; thus, preoperative PTH, preoperative serum calcium, and intraoperative PTH levels were not obtained on this patient. Preoperative imaging included Technetium 99-sestamibi parathyroid scan (n = 3), computed tomography (CT) neck (n = 4), and CT chest (n = 6). All eight procedures were performed by a single surgeon on a da Vinci Si console (Intuitive Surgical, Inc., Sunnyvale, CA) at a single institution. An ectopic parathyroid adenoma was removed from the mediastinum in all eight patients, confirmed on histopathologic examination. In six patients a hemithymectomy was performed to excise the ectopic adenoma, and in two patients enucleation of the adenoma was able to be performed. No procedures were converted to sternotomy. Intraoperative PTH decreased greater than 50% in all seven cases where it was measured. The average procedure lasted 108 minutes, with a range of 76–186 minutes. Mean estimated blood loss was 26 cc (range: 5–40 cc). There were no complications during any of the eight procedures, no postoperative hypocalcemia, and the median length of stay was one night in the hospital. There were no recurrences of hyperparathyroidism.

Procedure Details

Before the operation, localization of the lesion is significant as laterality dictates the surgical approach. For left-sided lesions, we approach from the left. Baseline PTH should be documented and if absent should be obtained on the morning of surgery. Double lumen endotracheal tube is necessary for single lung ventilation. The patient is positioned with the operative side flush with the table, and a rolled towel is placed under the patient's back to elevate the lateral chest wall. The ipsilateral arm is then placed on an armboard that is parallel to the table, effectively rotating the shoulder posteriorly for improved access to the axilla for proper port placement.

The patient is prepped widely in case of conversion to sternotomy and then draped in the usual sterile manner. In large-breasted women, the Ioban™ (3M, Maplewood, MN) drape is used to pull the ipsilateral breast medially, thereby displacing soft tissue and allowing easier port placement. The first port is in line with the nipple in approximately the fifth intercostal space in the mid-axillary line. This is a 12 mm AirSeal trocar. A 5 mm 30 degree thoracoscope is then utilized to visualize the other port insertions. The second port is an 8 mm robotic trocar, 8–10 cm anterior and superior to the camera port, in the second or third intercostal space. We routinely use a bariatric port for this port to avoid a pressure injury to the ipsilateral shoulder. The third port is 8–10 cm anterior and inferior to the camera port and is an 8 mm robotic trocar (Fig. 1). The robot is then brought in over the contralateral shoulder. The robot arms are docked and instruments inserted under direct visualization. The left hand instrument is cadiere forceps; the right is either a spatula, curved bipolar, or an L-hook.

OPEN IN VIEWER

FIG. 1.

Patient positioning for right-sided approach.

The mediastinum is examined and ipsilateral phrenic nerve identified. Dissection is started just medially to the phrenic nerve, and a plane is developed between the pericardium and the thymic fat. This avascular plane is continued superiorly, just medial to the internal mammary vein. The innominate vein is identified, and we clip vessels as needed when dissecting the thymus off of the innominate vein. If the adenoma is identified in thymic tissue and amenable to enucleation, the adenoma is removed in its entirety (Fig. 2). If not easily identified, a hemithymectomy is performed, and the specimen is examined to ensure removal of the adenoma. Postoperatively, calcium is checked on the evening of surgery. On postoperative day 1, laboratories, including calcium, magnesium, and PTH, are checked. The chest tube is removed, and the patient is discharged on calcium supplements and calcitriol.

OPEN IN VIEWER

FIG. 2.

Rendition of ectopic parathyroid adenoma visualized in thymic tissue.

Discussion

The parathyroid glands arise from endodermal epithelial cells. The inferior and superior parathyroid glands are derived from the third and fourth branchial pouches, respectively. During embryogenesis, the superior parathyroid glands descend with the lateral lobes of the thyroid gland into position in the neck. The inferior parathyroid glands are associated with the thymus gland and travel a relatively greater distance during descent. This increased distance in embryologic descent leads to increased irregularity in their final anatomic location. ³ Supernumerary parathyroid glands are not uncommon, as the prevalence of a fifth parathyroid gland has been found to be as high as 13%. ²² Since surgical approach depends greatly on location of the ectopic gland, we recommend preoperative workup with technetium-99m (99mTc) sestamibi (MIBI) and CT of the chest. Ultrasonography, while cost effective and widely available, is operator dependent, and the reported sensitivity fluctuates significantly (44%–87%). ²³ The combination of CT of the chest and MIBI scan has been demonstrated to have a sensitivity and specificity of 100%, yielding the correct diagnosis in all cases. ²⁴ Correct preoperative localization is imperative in preventing unnecessary morbidity to the patient. In 1994, Prinz et al. reported the first VATS procedures to successfully remove ectopic mediastinal parathyroid glands. ⁷ Before the advent of this minimally invasive technique, resection of an ectopic mediastinal parathyroid adenoma required sternotomy with high morbidity and mortality to the patient. Two of the original first four VATS mediastinal parathyroidectomy patients described by Prinz were discharged within 36 hours of operation, and none of the patients had a significant postoperative complication. When first reported in 2004 by Profanter et al., robot-assisted thoracoscopic surgery was described as an effective technique to treat primary hyperparathyroidism due to mediastinal adenoma with less harm to the patient. ⁸ The robot platform provides increased manual dexterity, improved vision of the field, and elimination of tremor. An additional benefit of utilizing the robot platform is the ability to perform a thymectomy if the ectopic parathyroid adenoma is not easily visualized. This case series demonstrates that robot-assisted thoracoscopic parathyroidectomy can be performed safely and effectively without complication as the majority of patients were discharged home after only one night in the hospital. In all cases, there was relatively low blood loss (<50 cc for all cases), and both patients with BMI greater than 40 did well postoperatively without complication and were discharged from the hospital after one night. Postoperative management for all patients included calcium and calcitriol supplementation, and no long-term complications have been noted in any patient.

Ethical Approval

Consent: Written consent was obtained by all patients before surgery, and all patient data have been deidentified; Humane treatment of animals: This work did not involve animals.