Abstract
Abstract
Background:
Ectopic parathyroid glands can present in a challenging location in the superior posterior mediastinum.
Methods:
Two patients with primary hyperparathyroidism were operated on for ectopic paraesophageal parathyroid glands in the superior posterior mediastinum. Sestamibi scan, computed tomography (CT) scan, and photon emission CT were used to identify the exact location of these glands. We describe a minimally invasive resection using a three-arm robotic-assisted thoracoscopic technique.
Results:
Both lesions were completely resected with using the port-based robotic approach with expedited recovery. There was no perioperative morbidity. Patient had low postoperative pain scores and improved symptomatically.
Conclusion:
Robotic approach for resection of superior posterior mediastinal parathyroids is safe and effective in this challenging operative location.
Introduction
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A more challenging place for ectopic glands is the location in the superior posterior mediastinum. Although these are less common, this location is particularly difficult to access for surgeons, and typically requires a thoracotomy. Paraesophageal lesions are thought to be displaced superior parathyroid glands that have descended into the chest in the tracheoesophageal groove. 3 Access to this tracheoesophageal grove high in the chest is difficult by both video-assisted thoracoscopic surgery (VATS) and open approach. In our experience, we have utilized a robotic-assisted approach for allowing completely port-based minimally invasive resection. We describe our robotic-assisted approach to resection of paraesophageal ectopic parathyroid glands in the superior posterior mediastinum based on 2 illustrative cases.
Patient Selection and Preoperative Workup
Case 1
A 70-year-old woman, former smoker with a history of a newly diagnosed gastric neuroendocrine tumor, hypertension, and diabetes mellitus was found to have hypercalcemia (10.5 mg/dL), and an elevated PTH (156.8 pg/mL). A PET scan was performed for her neuroendocrine tumor, which showed a hypermetabolic right paratracheal node. She underwent endoscopic ultrasound and biopsy of the presumed right paraesophageal lymph node, which demonstrated parathyroid tissue. A 99mTc sestamibi scintigraphy demonstrated uptake inferior to the right thyroid lobe. A computed tomography (CT) neck and chest showed an enhancing 2.1 × 1.2 cm nodule in the right upper mediastinum in the tracheoesophageal groove, which corresponds to the area of increased uptake on the parathyroid sestamibi scan (Fig. 1).
Case 2
A 74-year-old woman, never smoker, with a history of breast cancer, diabetes mellitus, coronary artery disease, chronic kidney disease, and hypertension, presented with cough and productive sputum, and was diagnosed with pneumonia. On examination, she was noted to have thyromegaly. She had been previously diagnosed and treated for osteoporosis, but denied other symptoms of hyperparathyroidism or renal disease. Blood tests revealed a leukocytosis of 11 and hypercalcemia (10.7 mg/dL). Further investigation revealed decreased phosphorous level at 2.8 mg/dL, elevated PTH >270 pg/dL, and a decreased thyroid-stimulating hormone of 0.97 mIU/L. Ultrasound of the neck showed a multinodular goiter. Fine needle aspiration biopsy of the biggest nodule was consistent with a benign colloid nodule. CT scan of the thorax revealed a 3.6 × 1.9 × 1.4 cm right paraesophageal mass in superior mediastinum just posterior and inferior to thyroid gland. A 99mTc sestamibi scintigraphy confirmed the diagnosis of an ectopic parathyroid gland (Fig. 2).
Operative Setup
The patient is initially placed supine on the operating room table. Single lumen endotracheal intubation is first performed after induction with general anesthesia. Fiberoptic bronchoscopy is then carried out. The single lumen tube is then exchanged for a double lumen endotracheal tube. Patient positioning for robotic resection of a right-sided posterior superior mediastinal mass requires a left lateral decubitus position, with careful padding of pressure points, an axillary roll, flexing the bed, and bean bag for stability. The patient is secured to the operating table with safety straps.
A three-arm robotic-assisted technique is used to perform the resection, currently utilizing the da Vinci Xi model (Intuitive Surgical, Sunnyvale, CA). The port sites are marked on the skin. A total of four ports are placed. The camera port (8 mm) is placed in the posterior axillary line in the eighth intercostal space. The posterior port (8 mm) for the robotic arm is placed 10 cm from the camera port. Given the location of the operative field in the superior posterior mediastinum, we adjusted to the placement of our anterior port (8 mm) from the typical location for lung surgery to the fifth intercostal space of the anterior axillary line. An accessory port (12 mm) port is placed in the 10th intercostal space (Fig. 3).
Trocar placement for a right-sided three-arm robotic-assisted approach.
Operative Technique
After inspection of the chest with the camera, the da Vinci Xi robot is docked to the robotic ports. We use a Cadiere grasper and a bipolar Maryland grasper through the other ports. To expose the superior mediastinum, the upper lobe is pulled inferiorly using a gauze roll on a grasper through the assistant port. Posterior to the right subclavian artery, the superior mediastinal pleural is incised using the bipolar forceps. The paraesophageal parathyroid is typically easily identified in this location. Additional methods for localizing the parathyroid can be employed using the Firefly technology, which is integrated in the da Vinci Xi robot. In some cases, the parathyroid shows autofluorescence; otherwise, parathyroid can be achieved by intraoperative injection of methylene blue, as previously described. 4 Once the mass is identified, it is grasped using the Cadiere and dissected circumferentially using the bipolar electrocautery. The parathyroid adenoma typically has a defined capsule, which allows us to grasp the gland and deliver it out of the mediastinum. Special care is made to use the bipolar to cauterize several small feeding blood vessels. In addition, caution is taken when using the bipolar cautery around the esophagus for concern of thermal injury. Thus, the mass is peeled off the esophagus bluntly using gauze rolls and dividing attachments with the bipolar cautery. Attention is paid to identify and spare the recurrent laryngeal nerve (Fig. 4). Once all attachments are dissected, the mass is removed in total through the assistant port using an endocatch bag. Complete resection of the parathyroid adenoma is confirmed by sending a piece for frozen section analysis, and by use of intraoperative PTH test. According to the Miami criterion, reduction of PTH level at 10 minutes after resection by 50% from the highest preoperative value should be confirmed. 5 Intercostal nerve blocks are performed using 0.25% ropivacaine with epinephrine. A 28F straight chest tube is placed through the sixth intercostal space robotic port and placed on −20 cm of suction. The lung is re-expanded under direct vision. The remaining incisions are closed in three layers.
Postoperative Management
Patients are admitted overnight. A patient-controlled anesthesia pump is used the day of surgery and transitioned to oral pain medication the next day. On postoperative day 1, chest tube is removed if output is <200 mL and patient is discharged home. Patients are given a calcium supplement upon discharge and calcium levels are checked on the morning after surgery and only if symptomatic afterward. We aim for discharge to home on postoperative day 1.
Outcomes
Operative times for two presented cases were 183 and 90 minutes, respectively. Estimated blood loss was between 5 and 10 mL. Both patients were extubated postoperatively and reported good pain control with median pain level of 4 (range 2–6) on a nurse recoded 10-point pain scale while hospitalized. Pathology confirmed ectopic parathyroid adenoma in both patients. Postresection PTH level normalized on day 1 in Case 1 and Case 2 at first follow-up. In addition, both patients reported marked symptomatic improvements with increased energy levels.
Comment
Ectopic parathyroid glands result from abnormal migration during embryogenesis. This occurs in 15%–20% of patients with hyperparathyroidism. 1 Most mediastinal parathyroid adenomas are not accessible with a transcervical approach, but require transthoracic exploration. A minimally invasive approach is favored given the risk for morbidity from a sternotomy or thoracotomy for these benign lesions. The paraesophageal location in the superior posterior mediastinum accounts for 5%–10% of ectopic glands, and presents a challenge to reach thoracoscopically, and even with thoracotomy. In a previous study, Ismail et al. reported on the use of robotic surgery for resection of 2 patients with parathyroids in the anterior mediastinum. Their series of 5 cases was able to show that a three-arm robotic-assisted dissection was feasible and effective, even in the setting of reoperation, with minimal associated morbidity. 1 Minimally invasive resection of paraesophageal ectopic parathyroids in the posterior superior mediastinum has not been previously described. Resection in this location nearing the thoracic inlet, typically require a high thoracotomy, as in the previous report by Ogawa et al. 6 In this location, parathyroids are crowded by vulnerable structures, such as the esophagus, the airway, subclavian artery, and recurrent laryngeal nerve. Based on our experience, the robotic-assisted approach is ideal for parathyroids in this location, and allows for minimally invasive completely port-based approach.
Successful resection of posterior mediastinal lesions depends largely on accurate preoperative localization of the ectopic glands. Diagnostic modalities such as an ultrasound of the neck, CT of the neck and chest, and parathyroid scintigraphy (sestamibi scan) are most beneficial for accurate localization and planning. For intraoperative localization, the use of robotic surgery is advantageous. Compared with a VATS approach, there is an enhanced view secondary to the three-dimensional camera. In addition, the wristed instruments allow for careful dissection, fine movements in small spaces, and the ability to reach and operate with precision, in the apex of the chest. Resection of superior posterior mediastinal lesions can be accomplished with the use of a three-arm approach rather than a fourth-arm approach. We find that the fourth arm is only used for retraction and manipulation of the lung, which we were able to accomplish with the assistant port. From a technical aspect, there can be thermal spread from the bipolar electrocautery, resulting to injury in adjacent structures. Therefore, when near the recurrent laryngeal nerve or esophagus, it is better to use blunt dissection. Finally, using this technique permits the use of carbon dioxide insufflation, which results in compressing of the lung parenchyma and flattening of the diaphragm, giving us a greater working space. Although we have not encountered a left-sided lesion, the robotic approach should be equally effective for resection of left-sided paraesophageal ectopic parathyroids above the aortic arch.
In summary, our experience shows that a robotic approach for paraesophageal parathyroids in the superior posterior mediastinum is safe and effective, and facilitates a quick recovery by avoiding a thoracotomy.
Footnotes
Disclosure Statement
Dr. Merritt is a speaker for Intuitive Surgical. There are no other relevant financial or personal conflicts of interests to disclose. This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.